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Science project, regeneration: do planaria really do it.

High School

Difficulty of Project

Safety issues.

Wear safety glasses, apron and plastic gloves.

Material Availability

Materials are readily available from Carolina Biological Supply and the local supermarket.

Approximate Time Required Completing the Project

2 months.  This includes collection, recording and analysis of data, summary of results and completion of bibliography.

To determine whether freshwater Planarian (flatworms) reproduce asexually by regeneration and whether the size of the segment will determine if regeneration will take place.

Materials and Equipment Required

• Planaria (Dugesia dorotocephala )
• glass containers
• 12 glass vials
• declorinated tap water
• raw beef liver
• a sharp knife or razor blade
• a glass plate or glass cover slip
• plastic gloves
• apron or old shirt as lab coat
• safety glasses
• paper towels

Introduction

Background information.

On the information level, this experiment serves to acquaint students with current information on the concept of regeneration, an asexual process of reproduction and the various studies that have been conducted on the process of regeneration using the flatworm, Planaria.  For over a century, the use of planaria as a basic specimen has lead to tremendous progress in the areas of genetics and currently in stem cell research. The amazing powers of regeneration demonstrated by freshwater planarians has intrigued scientists and resulted in an explosion of studies. Equipped with this investigation and knowledge the students too are both excited and motivated to not only read but conduct further research in this area.

This science fair experiment also serves to acquaint students with the essential processes of sciencing such as the importance of the use of a control, of identifying dependent and independent variables, of data collection, of pictorial and or graphic presentation of data and of being able to make better judgments as to the validity and reliability of their findings.  They take on the role of scientists and in the process they learn to act as one.

Research Terms

• Planaria    
• regeneration  
• asexual reproduction
• Turbellaria
• free living flatworms
• parasitic flatworms
• hermaphrodite

Research Questions

• What are Planaria?
• What are flatworms?
• Where are they found?
• Why are they considered simple and primitive?
• Why are they the subjects of a variety of experiments?
• Of what practical value are studies of regeneration in Planaria?  

Terms, Concepts and Questions to Start Background Research

• What is a control?  A control is the variable that is not changed in the experiment.
• What purpose does a control serve? It is used to make comparisons as to what changed or possibly caused the change.
• What are variables?  Variables are factors that can be changed in an experiment.
• What is an independent variable? The independent variable is the one that is changed in the experiment.
• What is a dependent variable? The dependent variable is the one that changes as a result of the change in the independent variable.

Charting and or Graphing Data

In each section of the experiment, use charts to display the obtained data such the following sample:

Charting Your Observations: Planaria Regeneration

Question: Will the size of the segment determine whether the organism will regenerate? Will the smaller pieces fail to regenerate?

Experimental Procedure

• State the problem you are going to investigate.
• Create and reproduce the data sheets you will use to record your observations.
• Gather all your materials.
• Put on your safety glasses, plastic gloves and apron.
• When you receive the Planaria, store them in glass containers filled with declorinated tap water. Feed them with beef liver twice a week. Keep them in a warm room, 68degrees F.
• When you are ready to begin, select 10 glass containers and label them as A1, A2, A3, B1, B2, B3, C1, C2, C3 and D1 and D2. Fill all of the containers to the ¾ level with declorinated tap water.
• You are going to use four sets of planaria, each set made up of two planaria.  Place the planarian on a glass slide and use a sharp blade or knife for the cutting.   The first set of two will be cut in half and placed into containers A1 and A2. The second set of two will be cut in thirds and place in containers B1 and B2. The third set will be cut into fourths and placed in containers C1and C2. The last set will remain whole and placed in Di and D2. The fourth set is your control.
• Keep all of the specimens in a warm room and replenish the beef liver twice a week.  
• You may wish to take photos each week. Continue and record your observations on a weekly basis for one month.
• Analyze the collected data and finalize your conclusion.
• Prepare your report and include all of the following: a clear statement of the problem, your hypothesis, namely what did you predict would occur, and a list of the materials used. Include the safety precautions taken. Describe the procedures used. Include all the data that were gathered. Include all charts. Explain the purpose of the control.  Formulate your conclusions. For dramatic value, you may include photos of the materials used or of you in the process of conducting this investigation. Include a bibliography of sources you used. You may wish to assess what you did and describe what you would do differently if you were to do this project again. You may wish to expand this research next year.  The process of regeneration is not only intriguing but may yield extensive benefits to the prolongation of life. What other studies might you conduct for this purpose?

Bibliography

 Goss, R. J. 1969. Principles of Regeneration. Academic Press, New York.

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Investigating Planarian Behavior and Regeneration

• Reproduction & Development
• Experimental Design

Resource Type

• Labs & Demos

Description

This activity allows students to observe their own planarian and then design an experiment to investigate how planarians regenerate. It supports viewing of the video Identifying Key Genes in Regeneration .

In this hands-on lab activity, students use planarians as a model organism to study the remarkable process of regeneration. Students first observe the planarian’s physical and behavioral attributes. Student teams then formulate a hypothesis regarding the regenerative ability of planarians. Over two to three weeks, students care for their planarians and collect data to test their hypothesis. After completing their experiments, students view a video to learn about the role of stem cells in regeneration.

This activity is based on an article that is provided as a download.

Student Learning Targets

Design and carry out an investigation.

Use a model organism to gather evidence to support or refute claims/hypotheses.

Estimated Time

anterior, flatworm, multipotency, neoblast, posterior, regeneration, stem cell, totipotency

Primary Literature

Accorsi, Alice, Monique M. Williams, Eric J. Ross, Sofia M. C. Robb, Sarah A. Elliott, Kimberly C. Tu, and Alejandro Sánchez Alvarado. “Hands-On Classroom Activities for Exploring Regeneration and Stem Cell Biology with Planarians.” The American Biology Teacher 79, 3 (2017): 208–223. https://doi.org/10.1525/abt.2017.79.3.208 .  

Terms of Use

Please see the Terms of Use for information on how this resource can be used.

Accessibility Level (WCAG compliance)

Version history, curriculum connections, ngss (2013).

HS-LS1-2, HS-LS1-4; SEP1, SEP3, SEP4

AP Biology (2019)

ENE-3.D, IST-2.A, IST-2.D, IST-3.A; SP3

IB Biology (2016)

Common core (2010).

ELA.RST.9–12.3

Vision and Change (2009)

Explore related content, other resources about planaria.

Other Related Resources

Planaria Regeneration Experiment for the High School Science Class

• Categories : Lesson plans for high school science
• Tags : High school lesson plans & tips

What is Planaria?

Planaria belongs to Kingdom Animalia, Phylum Platyhelminthes (flat worms), Class Turbellaria, Order Seriata, and Family Planariidae. Planaria is the generic name for all flatworms that belong to Family Planariidae whatever their genus names are. The most popular genera (sing. genus) of planaria used in laboratory experiments and scientific researches are those that belong to genus Dugesia, Planaria, and Schmidtea.The genus Dugesia is commonly used in high school biology experiments to demonstrate regeneration. The other planarian genera are more commonly used in advance researches on molecular biology, genetics, and developmental biology.

Planaria flatworms live independently; they don’t parasitize any other organism in order to live. They are found both in saltwater and freshwater environments and eat live and dead small animals.

The planaria flatworm has a body length ranging from 3 to 12 mm. It has a head with muscular mouth used to suck food and two eye-spots used to detect the presence of light. The planaria avoids light because it is a potential source of heat that can dehydrate the flatworm. The elongated tail has cilia on the ventral dermis and these are used by the worm to glide on the mucus that it has secreted.

The planaria reproduces sexually or asexually. Sexually, the flatworms produce gametes (sex cells) to produce offsprings. Two flatworms fuse their gametes to form eggs that will hatch later on. Asexually, planaria flatworms can reproduce through regeneration. The flatworms can cut a portion of their tails and these tails would regenerate heads. The new flatworms would grow and live on their own.

Planaria Regeneration

The planaria has an amazing capability to regenerate its lost body part. When the flatworm is cut crosswise separating the head from the tail, the tail will regenerate the lost head and the head will regenerate the lost tail. The same thing happens when the flatworm is cut lengthwise, the lost body parts are regenerated until each piece became another flatworm with complete body parts. The tail can be cut crosswise into three or four and they will all regenerate a head. Note that the head is regenerated first before tail elongation occurs.

Design of the Experiment

Planaria flatworms can be found in fresh water ponds especially during spring. The teacher can get some flatworms in these ponds for the experiment. There are also shops that sell biological supplies including planarian flatworms. The teacher can buy some flatworms in these shops. The flatworms should be kept in glass containers with some water (preferably spring water) before the experiment. The flatworms need water to prevent dehydration.

Before the experiment, the teacher should explain clearly the objective(s) of the experiment to the students. The main objective of course is to demonstrate regeneration.

The major materials to be used in the experiment are petri dishes, scalpel, and spring water.

The class can be divided into groups where each group will set up their own experiment or there would only be one set up for the whole class depending on the number of flatworms or materials available.

The teacher may instruct the students to observe the anatomy of the flatworms and the movement of the flatworms. The teacher can also ask the students to draw and label the flatworms.

The teacher will demonstrate to the class on how to dissect the flatworms into multiple parts. The figure on the right shows the different ways on how to dissect the flatworms. The figure shows that the flatworm can be dissected into five different ways, so at least five petri dishes are needed for each set up. The scalpel is used to cut the flatworms. The teacher should guide the students on cutting the flatworms. The petri dishes should be filled with some water to prevent dehydration on the flatworms. The flatworm should be kept in the laboratory room where light intensity is minimal.

After the dissection, the students will observe the flatworms daily. They should note and record any changes on the flatworms. After few days, they would notice that the flatworms regenerate their lost body parts.

The experiment should be followed by a classroom discussion about the ability of the flatworms to regenerate their lost body parts. The teacher should discuss the relevance of the experiment including its possible applications in the field of medicine.

Planaria Regeneration . Retrieved on May 22, 2009

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• Why We’re Unique

Regeneration in sponges, Paramecia, Planaria, etc.

Introduction: (initial observation).

Certain invertebrate aquatic animals are able to regenerate their missing parts. This regeneration ability in some animals is so strong that if you cut the animal in half, each half will grow to a complete a whole new animal. The tail half regenerates a new head and the head half regenerates a new tail.

This unusual ability also is a method of asexual reproduction for such animals.

Regeneration abilities vary among these animals; however, they are all subject of attention by scientists who are trying to identify the genes responsible for such regeneration.

The purpose of this project is to observe the regeneration ability of these animals. I may either select sponges or planarians for my experiments because these two are visible to the naked eye and I do not have to use microscope and complex tools for my observations. I may also try to study the effect of one environmental factor such as temperature or pH on the rate of regeneration.

This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “ Ask Question ” button on the top of this page to send me a message.

If you are new in doing science project, click on “ How to Start ” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.  

Project advisor

Information Gathering:

Find out invertebrate aquatic animals and their reproduction methods. Read books, magazines or ask professionals who might know in order to learn about regeneration in plants and animals. Also gather information about the specific animal that you want to study (sponge, planarian,…). Keep track of where you got your information from.

Following are samples of information that you may gather.

What is regeneration?

Regeneration is replacement of parts that have been cut off or otherwise removed:

By growth and division of cells, often dedifferentiation & redifferentiation, & also cell rearrangements.

Some kinds of animals can regenerate all parts of their bodies: sponges, Hydra, Planaria, and some sea squirts . Note that all these also undergo asexual reproduction =budding of new individuals from the body of another. Most or all starfish can regenerate arms from the body; but only those of one genus (Linckia) can regenerate the whole body from arms! (contrary to what most people think) These deliberately tear arms off as a means of asexual reproduction.

Sponges are the simplest form of multi-cellular animals. A sponge is a bottom-dwelling creature which attaches itself to something solid in a place where it can find enough food to grow. The scientific name for sponges is “Porifera,” which translates into “pore-bearing.”

Source…

Almost all sponges pump water to obtain nutrients and oxygen. A sponge is covered with tiny pores which lead internally to a system of canals and eventually out to one or more larger holes. These canals exist to move water through the sponge’s body. Lining these canals are special collar cells. The collar cells force water through the sponge which brings oxygen and nutrients while removing carbon dioxide and waste. The collar cells are how sponges feed. The water brings with it bacteria and other organisms which the cells capture and filter out.

How Do Sponges Reproduce?

Most sponges are both male and female. During mating, one sponge plays the male role while the other plays the female role, even though both are capable of playing either role. A sponge may play a female role one time and a male role the next time. Sperm is released by the “male” sponge and enters the “female” sponge. After internal fertilization, larvae is released. After floating around for a few days, they settle down and start growing.

Sponges can regenerate the entire organism from just a conglomeration of their cells.

Planarians: 

These  flatworms  can regenerate the entire body from just a small piece. They do this by the proliferation and differentiation of the  totipotent stem cells  that it retains in its body throughout its life.

Paramecia can not regenerate missing parts like Planarians and sponges; however they also have some unusual properties or abilities that I like to call degeneration.

In paramecia, if you (somehow) rotate a small area of the animal’s surface so that the power strokes of the cilia in this area are pointing backward, then providing that this area is about half-way between the anterior and posterior ends (which is the plane in which these animals divide after mitosis), then both offspring will have areas of reversed cilia; and this will be inherited by all their offspring, without limit.

If you fuse two Paramecia, back to back, so that they have two mouths on opposite sides (Janus morphology) then this double body will be inherited by both daughter cells each time mitotic divisions occur.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to experiment and observe the regeneration process in planarians or sponges. Record your daily observation so you can use it to answer questions like:

• What is the rate of regeneration in planarians?

You can also perform additional experiments to determine the effect of environmental factors on the regeneration of planarians. Sample questions are:

• How does pH affect the rate of regeneration in planarians?
• How does light affect the rate of regeneration in planarians?
• How does temperature affect the rate of regeneration in planarians?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

For the first question, we need to determine how long it takes for a fragment of planarian to regenerate and become a complete animal.

Independent variable is the size of fragment (1/2, 1/4, …)

Dependent variable is time to fully regenerate.

Controlled variables are all environmental variables including temperature, pH, light.

Constants are experiment method, procedures and growth medium.

For the second question pH is the independent variable. (fragment size will also be added to the list of constants)

For the third question light is the independent variable. (fragment size will also be added to the list of constants)

For the fourth question temperature is the independent variable. (fragment size will also be added to the list of constants)

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

Following are sample hypothesis for the four questions that I have proposed:

• The larger a fragment of planarian, the less it takes to regenerate.
• pH has no affect on the rate of regeneration of planarians.
• Planarians regenerate faster in darkness.
• Planarians regenerate faster in warm water.

Note that the results of your experiments may show that your hypothesis has been wrong. Also it is a good practice to offer an explanation with each hypothesis describing why you are adopting this hypothesis.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1: Planaria Regeneration Rate

Introduction

Many animals are capable of regeneration of lost parts to some extent. In this experiment we will examine regeneration in Dugesia sp. (a planarian), a common freshwater flatworm. These animals have considerable powers of regeneration, and their ability to regenerate has been investigated in great detail. The body is polarized on the anterior-posterior axis. In other words, if you cut off the head the head will grow a new body, and the body will grow a new head. Also, anterior regions grow fastest.

• 2 complete petri dishes (top and bottom)
• Dugesia (from pond or Carolina L210)
• razor blades

Preparation

You must have fully grown planaria for this experiment. If you are growing planaria from culture, you must follow the instructions that you receive with the culture to grow planaria so they will be ready for this experiment. If you are collecting planaria from a pond, you must isolate planaria from algae and other invertebrates that may exist in water.

How to isolate planaria from pond water?

Add tap water to the bottoms of a petri dishes. Take some pond algae and put it in the bottom of another petri-dish. Use an eye dropper to suck up a planarian and put it in the first petri dish. Be sure not to include other visible invertebrates as they may be predators of Dugesia. Collect 20 individuals if possible (keep track by counting them!). Throw away the algae, wash the plate and eye dropper. keep your 20 isolated planarians for this experiment.

Experiment:

Half fill 2 Petri dishes with simulated pond water or aged tap water. This water contains most of the nutrients but none of the micro-organisms of ordinary pond water.

Use an eye dropper to transfer 10 Planaria to each petri-dish.

Label one petri-dish containing 10 planaria and somewater as “ control ” and close the top.

Place the other petri-dish on ice so planaria will become motionless.

With the scalpel or razor blade, quickly cut each Planaria in half. Cuts can be transverse, or longitudinal. Cut exactly half of the worms. Leave both halves in the petri-dish.

Close the lid and label this petri-dish with “ Cut “.

Place the Petri dishes in a dark place at room temperature or in an incubator.

Examine the Planaria for a few minutes every 3 days. Remove any dead sections immediately. Examine the Planaria under a magnifier or dissecting microscope and make sketches to show the changes. Note how many have full, partial, or no regeneration.

Record your observations in a table like this:

Number of live worms in petri-dishes

Any invertebrate zoology text.

Rose, S.M. 1970. Regeneration. Appleton-Century-Crofts, NY

Moraczewski, J. 1977. Asexual reproduction and regeneration of Catenula. Zoomorphologie 88:65-80.

Whitten, R.H. and W.R. Pendergrass. 1980. Carolina protozoa and invertebrates manual. Carolina Biological Supply Co., Burlington, NC. 34 pp.

http://biocourse.bio.tamu.edu/course/zool344/Lab101A.PDF

Experiment 2: Effect of pH on the rate of Regeneration in planaria

Introduction:

Scientists often want to know the affect of environmental factors on the rate of reproduction in different animals. Regeneration for planaria is also a way of asexual reproduction, so it well qualifies for such studies.

This experiment is identical to the previous experiment. Instead of 20 planaria, use 40 planaria in 4 petri-dishes (10 planaria per dish). One dish will be control and 3 others will have cut planaria. These last 3 dishes will have three different pH. One will be normal water pH. The other will be acidic (by one drop of acetic acid) and the last one will be alkaline (by one drop of ammonia solution).

Record 3 results table, one for each pH (Alkaline, normal, acidic). Use the same control for all three results tables.

More Experiments: Effect of other factors such as temperature or light on the rate of Regeneration in planaria or sponges

Many other experiments can be designed to test the effects of certain factors (independent variables) on the rate of regeneration on planarians and sponges.

The structure and procedures of most such experiments are similar to the experiment 1 and 2 described above.

Sponge growth Experiment

Sponges are very simple animals whose cells are not organized into discrete tissues. They are capable of incredible regeneration. The classic experiment to demonstrate this property is to force a sponge through a fine mesh to separate the cells. After a while, the cells re-aggregate by type and reform the sponge’s body.

Obtain a piece of live Microciona or any other marine sponge. Press it through a metal or nylon mesh into seawater. This will break the sponge in small clumps of cells. These clumps will remain suspended in sea water. Examine a drop of the suspension under a compound microscope or magnifier glass. You will see small clumps of cells.

Prepare a series of dilutions in seawater from the original suspension so that you have samples of decreasing densities. Make your dilutions 100%, 50%, 25%, and 10% solutions of the original suspension.

Get 8 identical beakers or glass cups and half fill two beakers with each of the dilutions. Label the beakers with the dilution. Also label one beaker of each dilution as control. (So you will have one control for each dilution).

Cover the control beakers and place them in refrigerator. Keep other beakers at room temperature (72-80ºF) and use an aquarium pump to delver air to these cups a few hours each day.

Make observations of cell clumps every 2 days using a microscope or magnifier glass. If the pieces are still very small, you may use a pipette to transfer a drop of the suspension to a microscope slide and then view it under a the microscope.

Does temperature affect regeneration of sponges?

Materials and Equipment:

Results of experiment (observation):.

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

No calculation is required for this experiment.

Summary of Results: 

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

List of References

• Invertebrate Animals
• Paramecia, a food for newly hatched fish
• Asexual and sexual reproduction in paramecia
• Regeneration
• Encyclopedia of Marine Life
• Animal Diversity
• Biology of Planaria
• Worms in your aquarium
• Buy Planaria Online
• Biology of Paramecia

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• Perspect Behav Sci
• v.41(2); 2018 Nov

Behavioral Research with Planaria

Neil deochand.

1 Health and Human Services Department, University of Cincinnati, 450H Teachers-Dyer Complex, Cincinnati, OH 45221 USA

Mack S. Costello

2 Department of Psychology, Rider University, 2083 Lawrenceville Road, Lawrenceville, NJ 08648 USA

Michelle E. Deochand

3 Cincinnati, OH USA

Associated Data

This article serves as a brief primer on planaria for behavior scientists. In the 1950s and 1960s, McConnell’s planarian laboratory posited that conditioned behavior could transfer after regeneration, and through cannibalization of trained planaria. These studies, the responses, and replications have been collectively referred to as the “planarian controversy.” Successful behavioral assays still require refinement with this organism, but they could add valuable insight into our conceptualization of memory and learning. We discuss how the planarian’s distinctive biology enables an examination of biobehavioral interaction models, and what behavior scientists must consider if they are to advance behavioral research with this organism. Suggestions for academics interested in building planaria learning laboratories are offered.

Electronic supplementary material

The online version of this article (10.1007/s40614-018-00176-w) contains supplementary material, which is available to authorized users.

Nonhuman animal research contributes substantially to understanding human behavior (see Lattal, 2001 ), and continues to inform theory and clinical treatment (American Psychological Association [APA], 2017 ). Planaria are organisms with a unique research history, and provide a model for examining complex learning within their simple behavioral repertoire. However, species used in research appear to be selected based on convention, or ease of access. At first, pigeons were selected to emphasize that mammalian brains and associated cognitive processes were not required to demonstrate complex behavior (e.g., Epstein, 1981 ), but they have remained a conventional research model. The American Psychological Association (APA) noted that 90% of nonhuman psychology research uses rodents and avians (APA, n.d. ). Focusing on the “white rat” to the exclusion of other species minimizes the breadth of scientific discovery (Breland & Breland, 1961 ).

Traditional behavior science uses a limited variety of species in research, potentially leaving undiscovered biological mechanisms and phylogenic contingencies particular to each species (Breland & Breland, 1961 ; Skinner, 1966 ). Zimmermann, Watkins, and Poling ( 2015 ) reviewed animal subjects in studies published in the Journal of the Experimental Analysis of Behavior ( JEAB ) between 1958 and 2013. The most common subjects were avians (47.9% pigeons), rats (24.2%), humans (17%), nonhuman primates (7.5%), and other (5.2%). 1 The majority in the “other” category comprise vertebrates like fish and reptiles. Invertebrate species accounted for 0.13% of research studies that appeared in JEAB between 1958 and 2007 (Sokolowski, Disma, & Abramson, 2010 ). Despite invertebrates dominating a disproportionate amount of the animal kingdom (almost 95%), they are on the fringe of research efforts in psychology (Bitterman, 1965 ; Corning & Lahue, 1972 ; McConnell, 1966 ). Contrary to anthropocentric opinion, a spine is not a prerequisite for neural complexity, nor is one required to confer insight into human behavior.

Invertebrate research is worthwhile for many reasons. Such research is inexpensive relative to vertebrate models, and the care and maintenance of the animals is less labor intensive. In addition, institutions utilizing an institutional animal care and use committee (IACUC) typically waive regulatory oversight for invertebrate use in research and teaching activities (regardless, all activities should be ethically conducted). Numerous species like aplysia (Downey & Jahan-Parwar, 1972 ), blow flies (Sokolowski et al., 2010 ), cockroaches (Dixon, Daar, Gunnarsson, Johnson, & Shayter, 2016 ), green crabs (Abramson & Feinman, 1990 ), honeybees (Grossmann, 1973 ), and planaria (Shomrat & Levin, 2013 ) have been used in operant research, and far more have been used in the respondent literature. Skinner, known for work with pigeons, also conducted research with ants (Barnes & Skinner, 1930 ).

The purpose of this article is to be a primer on planaria behavior. We start by introducing the organism, then cover classic behavior science research on planaria and its implications, then finally we discuss what can be learned by integrating this organism in modern behavior science. There are several reasons to seriously consider the experimental analysis of planarian behavior. First, although the evolutionary lineages of planaria and humans diverged long ago, the neurobiology of a planarian is surprisingly similar to that of vertebrates, and it is considered one of the first organisms to have a “true brain” (Pagán, 2014 ). Second, due to their ability to regenerate after being dissected there are many interesting research questions for experimental analysis. Consider that it may be possible to train a planarian to engage in a target behavior, then dissect the planarian and determine if the head or tail segment retained prior training. Lastly, Katz ( 1978 ) proposed many years ago that planaria would be useful in university laboratories, and they continue to be recommended for that purpose despite being rarely used (Chicas-Mosier & Abramson, 2015 ).

Introducing the Planarian

Planaria belong to the phylum Platy-helminthes , which translates to “flat-worm.” Figure ​ Figure1 1 depicts the basic anatomical layout of the planarian. Sizes vary by species, where some are as short as 1 millimeter in length, others as long as 90 millimeters (Pagán, 2014 ). Most planaria species are found in freshwater (Reddien & Alvarado, 2004 ), but marine and terrestrial species exist (Pagán, 2014 ). Aquatic species use cilia and tail motion to glide in water. Planaria are sensitive to many stimuli including: chemical gradients, texture, vibration, electric fields, weak gamma radiation, magnetic fields, light (Nicolas, Abramson, & Levin, 2008 ), and gravity (Adell, Saló, Van Loon, & Auletta, 2014 ), so it is essential to minimize background interference.

Simplified anatomical depiction of the planarian CNS. The anterior contains the head, brain and eyes; the middle comprises the abdominal trunk and pharynx. Ingested nutrients diffuse to the rest of the body

Feeding in the Planaria

Evasion and hunting patterns, potentially mediated by activity or ability to adhere to surfaces, vary by species (Best, 1960 ). Although most flat worms are parasitic, planaria are opportunistic predators and scavengers (Pagán, 2014 ), preying predominantly upon small insects, larvae, and other invertebrates (Reddien & Alvarado, 2004 ). Freshwater planaria commence the feeding process with a light investigatory head touch to the food, then the head is retracted. Finally, the planarian quickly wraps around and latches on the food (Best, 1960 ). Chemical signals in the water play a major role in localizing food. Planaria are also attracted to live prey that produce disturbances in the water (Reynoldson & Young, 1963 ). They leave a mucus trail on surfaces they contact, which assists in surface adherence and capturing prey (Bocchinfuso et al., 2012 ). In research, planaria have displayed a preference for struggling prey (trapped with petroleum jelly) compared to inert controls (Reynoldson & Young, 1963 ). After ingesting food, locomotion and responsivity to stimuli is much reduced. If stressed sufficiently after eating, planaria will expel previously ingested food enabling more efficient evasion. Latency to feed increases in the presence of novel stimuli, often requiring a habituation period prior to eating (Best & Rubinstein, 1962 ). Planaria can be attracted to water movement without the presence of prey (Allen, 1915 ). This is possibly a discrimination issue, that is to say planaria may “confuse” the movement with presence of prey.

In laboratory conditions planaria can thrive on raw liver or brine shrimp, but they will eat almost any animal tissue readily (Jenkins, 1967 ). Muscle tissue is reportedly not as effective for maintaining planarian growth (McConnell, 1967 ). Freezing is standard for laboratory feeding, but there is a slight reduction in the growth factor compared to fresh samples (McConnell, 1965).

Locomotion in the Planaria

In general, planaria avoid open spaces (Talbot & Schötz, 2011 ) and demonstrate a preference for container walls (Akiyama, Agata, & Inoue, 2015 ). Two-dimensional tracking is usually sufficient to characterize locomotion of planaria. In laboratory environments the upward lifting of the head is minimized due to the shallow depth (1 cm) of the water in petri dishes, and because this action is usually made in response to food or obstacles encountered (Talbot & Schötz, 2011 ). S. mediterranea average speeds up to 2mms -1 , which is about 10 times faster when compared to other invertebrates like C. elegans (Talbot & Schötz, 2011 ). Speed has been reported to be stable within size differences of 1–2.6 cm between planaraia (Raffa, Holland, & Schulingkamp, 2001 ). There are several dimensions of movement one could measure, such as velocity, time immobile, the number and direction of turns, contractions not resulting in direction changes, and worm paths depicting density of locations frequented. The head region, containing the brain, is important in movement and orientating toward or away from stimuli. If the head is separated it will move away from the less mobile headless body (Reddien & Alvarado, 2004 ).

When a planarian is placed in a novel environment, there is an initial exploratory phase. After 5–30 minutes alone in a petri dish, a planarian will become immobile and “scrunch” their head into their body. This action can also be elicited by physically touching the planarian’s head and possibly confers some protection to the brain region. While scrunched up, a planarian may be less sensitive to stimulation that would previous elicit or evoke a response. Researchers have opted to poke, shock, or pipette planaria to locomotion. To purposefully immobilize planaria anesthetizing agents, chilled water, or thicker mediums to slow movement can be used (Dexter, Tamme, Lind, & Collins, 2014 ). Researchers developed a chip that renders a planarian immobile without side-effects (Dexter et al., 2014 ). After dissection, both head and tail segments will typically stay close to concave curves of outer walls of containers and from this position they are less likely to engage in head turning unless out in the open (Akiyama et al., 2015 ).

Drug Effects in Relation to Movement

The planaria central nervous system (CNS) contains nearly every neurotransmitter found in mammalian vertebrates, and for this reason they have been used extensively pharmacological research (Nicolas et al., 2008 ). Planaria are administered pharmacological agents by bathing the worm in a drug solution. Ethanol mixed in a 3% in water solution has been shown to suppress locomotor activity in Schmidtea mediterranea (3–6 mm in size) with no permanent decline in their regenerative ability, even after repeated exposure (Stevenson & Beane, 2010 ). Acute exposure to stimulants does not always result in increased locomotion, possibly because planaria move at their top speeds. Stimulant withdrawal can result in decreases in movement (Ramoz et al., 2012 ). Mephedrone, cocaine, and nicotine have been shown to induce stereotypic contractions, referred to as screw-like or “C-like” hyperkinesias (Pagán et al., 2013 ; Raffa et al., 2001 ; Ramoz et al., 2012 ). Cocaine requires an intact brain to induce contractions, because decapitated segments do not contract, whereas nicotine induces this behavior in the head or headless segments (Pagán et al., 2013 ). It should be noted that planarian size should be reported because this could affect the pharmacokinetics of drug metallization.

Sexual Behavior

Planaria can reproduce asexually by fission, where a worm divides into two or more sections, with each piece regenerating to form genetic clones. Dissection imitates asexual fission, which occurs naturally when a planarian gets larger or is exposed to stressors. Some describe this process as potentially resulting in an “immortal life-history” for planaria (Sahu, Dattani, & Aboobaker, 2017 ). Certain species engage in sexual reproduction as cross-fertilizing hermaphrodites (Reddien & Alvarado, 2004 ), laying cocoons that give birth to hatchlings (Sahu et al., 2017 ). Sexuality reportedly can be induced in some planaria by exposing them to colder temperatures then returning them to room temperatures (Jenkins, 1967 ). Sex allocation in some flatworms can be determined by “penis fencing,” where partners stab one another until injecting enough sperm to assign one as female (Ramm, 2016 ).

Group and Species Behavior

After acclimatizing to an environment, planaria of different species cluster together (Reynierse, 1967 ; Reynierse & Ellis, 1967 ; Reynierse, Gleason, & Ottemann, 1969 ). Planaria engage in mutually protective behaviors such as crowding together under ultraviolet stimulation, which confers some protection from the harmful effects of the radiation (Allee & Wilder, 1939 ). Certain species are more likely to engage in cannibalization of other species. For example, D. tigrina will attack C. foremani at night and when starved, but attacks do not occur in the other direction even though C. foremani predates on larger more active prey like the mosquito wriggler (Best, 1960 ). Housing species separately could prevent cannibalization and transference of diseases between colonies.

Species Used in Research

Biologists interested in behavior have studied several species of planaria. Dugesia japonica , Schmidtea mediterranea , and Girardia tigrina are often preferred models (Auletta, Adell, Colagè, D’Ambrosio, & Salò, 2012 ). S. mediterranea (see Fig. ​ Fig.2) 2 ) have been genomically sequenced, making them an attractive option for molecular biologists (Nicolas et al., 2008 ), and D. japonica are sometimes favored for behavioral experiments because they are highly active and appear to adapt well to training paradigms (Shomrat & Levin, 2013 ).

A1 depicts a single 10 mm planarian ( S. mediterranea ) at 12x magnification. A2 depicts a group of S. mediterranea on a chilled plate to slow movement for image capturing

Classic Behavior Science Research

The planarian brain is actively involved in avoidance paradigms, satiation reflexes, and mating behavior (Egger, Gschwentner, & Rieger, 2007 ). The planaria can perfectly regenerate all elements of its morphology, including its head and brain. Indeed, these regenerative abilities exceed many other animal regeneration capabilities including the axetlotl, spiny mouse, and zebrafish (Newmark & Alvarado, 2002 ). Researchers have been curious what learning, if any, from a trained planaria transfers to the head or tail portions after dissection. Behavior science has developed numerous learning models, and the planarian could be the key to unlocking what physiological changes relate to different psychological learning processes. Unfortunately, the planarian behavioral training literature contains many controversial findings and misinterpretations. Behavior science as a field is positioned to offer guidance where there has been a failure to understand crucial elements in the conditioning literature.

Respondent Conditioning

The “planarian controversy” stems from early classical conditioning experiments using light and shock pairings with turns and contractions (Corning & Riccio, 1970 ). Thompson and McConnell ( 1955 ) attempted to condition turns and contractions in G. dorotocephala using a group design . The conditioned stimulus (CS) was light, and the unconditioned stimulus (US) was shock. In the experimental group, light was presented for 3 s, with shock overlapping the final 1 s. To determine if conditioning occurred number of turns and contractions were examined by comparing three control groups, one where light was presented in the same manner but without shock (light control [LC]), one with no experimental stimuli (response control [RC]) and one in which shock was presented the same number of times as the experimental group (shock control [SC]). Figure ​ Figure3 3 depicts turns and contractions LC or RC groups’ decreased in frequency or were stable, but the experimental group showed response increases, supporting the premise that conditioning occurred. The SC group was used to ascertain if shock sensitized responding to light. Thompson and McConnell ( 1955 ) noted minimal differences between the first and last 15 trials. McConnell, Jacobson, and Kimble ( 1959 ) extended this earlier work by dissecting the worms post training, and examining learning in regenerated segments. A response control group received no directed training, but they were also cut in half to eliminate the possibility that the act of dissection sensitized their responsiveness to shock or light. Their results offered some support that conditioning survived the regeneration process, surprisingly for both the head and tail sections (McConnell et al., 1959 ). However, critiques included that the study was not well-controlled (Halas, James, & Knutson, 1962 ).

Percentage of turns and contractions of control and conditioned worms. Adapted from Thompson and McConnell ( 1955 )

Halas et al. ( 1962 ) replicated Thompson and McConnell’s study. Halas et al. found smaller differences between experimental and LC groups than in Thompson and McConnell’s original study, but otherwise noted that their data were similar. Halas et al. suggested that light actually served as a weak US for turns or contractions, and that the results of the experimental group could be better explained through sensitization. Halas et al. ( 1962 ) were correct in identifying light as a weak US, however, they were incorrect in their interpretation of sensitization. Visual analysis of their results (see Fig. ​ Fig.4) 4 ) support the notion that conditioning occurred, specifically the experimental group data are steady or upward trending, whereas control data are clearly trending down. An examination of both Halas et al. and Thompson and McConnell’s data show that there was no case for sensitization, because in the SC groups there were decreasing turns with continued trials, and little to no differences in contractions. Halas et al. ( 1962 ) had used null-hypothesis significance testing (NHST) to conclude differences between the experimental group and controls were not significant, despite the clear visual analysis of data (It should be note that NHST in psychology is deeply problematic [Branch, 2014 ]). The social context of the science at the time is fascinating, and several records are available indicating that McConnell was a controversial figure in science, and potentially this could have motivated others to discredit his findings (e.g., Duhaime-Ross, 2015 ).

Percentage of turns and contractions of control and conditioned worms. Adapted from Halas et al. ( 1962 )

Halas et al. ( 1962 ) surmised responding was a product of some process other than conditioning. Arguments against conditioning were presented two ways. Either the shock sensitized responding to light by altering the planarian’s physiological response to any stimuli (as noted above, data sets from SC groups across the studies do not support this interpretation). Pseudo-conditioning was presented as the alternative argument, because potentially random presentations of light and shock stimuli could result in similar results to the experimental groups in the classic studies (Travis, 1981 ). Baxter and Kimmel ( 1963 ) added an unpaired control group to Thompson and McConnell’s ( 1955 ) procedure, which received the same light or shock stimuli as the experimental group except they were separated by 15 s. Conditioned contractions increased over time for the experimental group and decreased for the unpaired group, but differences between the groups disappeared quickly during extinction. Jacobson, Horowitz, and Fried ( 1967 ) established that the same light-shock forward pairing resulted in higher responses compared to backward or simultaneous presentations. Both studies substantially weakened pseudo-conditioning and sensitization as potential explanations for Thompson and McConnell’s ( 1955 ) results (Rilling, 1996 ).

The planarian controversy culminated when McConnell ( 1962 ) posited that respondent learning could transfer from trained to untrained planaria through cannibalization. The study included a lack of contemporaneous controls related to the biology of the organism (i.e., no cannibalized shock alone or cannibalized light alone controls were used) leading critics to quickly attribute results to again rely on pseudo-conditioning or sensitization to refute the results, rather than “memory transfer” (Walker, 1966 ; Walker & Milton, 1966 ). Much of this research was denigrated as folklore within psychology, and largely forgotten (Duhaime-Ross, 2015 ). Since then, molecular experiments examining RNA interference have offered support for McConnell’s results and interpretation (Smalheiser, Manev, & Costa, 2001 ).

Operant Responding

A majority of behavioral research with planaria has used classical conditioning procedures (Shomrat & Levin, 2013 ), but there have been operant conditioning experiments (Crawford & Skeen, 1967 ; Chicas-Mosier & Abramson, 2015 ; Krantz, 1964 ; Lee, 1963 ; Wells, Jennings, & Davis, 1966 ). Lee ( 1963 ) attempted to condition a free operant response. When a planarian passed through a photoelectric cell beam, this response was recorded and reinforced by the termination of the aversive stimulus of light (a negative reinforcement procedure). In an extinction phase, the rate of passing through the beam decreased to near zero levels. Krantz ( 1964 ) and Crawford and Skeen ( 1967 ) successfully replicated Lee’s operant responding study, also with yoked controls. Although results were clear, Halas ( 1963 ) critiqued that passing through the beam may not have been an operant response, suggesting it was an artifact of turning the light on. This would have resulted in increased locomotor activity that altered the probability that the planarian would accidentally touch the beam, and subsequently turn off the light source. After a period of activity planaria usually reduce movement particularly in the dark, thus resulting in the planaria already being closer to the photobeam, and more likely to turn it off. Halas ( 1963 ) aptly debated whether this was in fact an instrumental response, but with Skinnerian conceptualizations of operant behavior this distinction becomes more difficult. We will return to the necessity and validity of the operant–respondent distinction below.

Chicas-Mosier and Abramson ( 2015 ) reported a procedure for shaping planaria to move longer distances along the edge of a half petri dish to seek water reinforcement. This was based on early maze work where water was used as reinforcement (Best, 1965 ) combined with Skinnerian shaping. This procedure was robust in design demonstrating that controls do not travel as fast without the training procedure.

The slime trails left by planaria can serve as cues in maze learning based on a preference for “slimed areas” (McConnell, 1966 ). A simple preparation reducing planaria handling and the need for hand shaping is the modified Van Oye Maze, which will be discussed in more detail in the section “Opportunities for University Learning Labs,” below (Wells et al., 1966 ).

Operant–Respondent Distinction

Within behavior science, even with traditional animal models, there are challenges to distinguish between operant and respondent processes. The overlapping interactive effects in processes such as autoshaping, differential outcomes effect, unsignaled avoidance, adjunctive schedule induced behavior, and conditioned suppression lead to these challenges (Pear & Eldridge, 1984 ). Theorists using biobehavioral models have concluded that operant and respondent conditioning are one process with different procedures (e.g., Donahoe & Palmer, 2004 ). The procedural definitions have been based on structural ordering of events related to behavior, but these purely behavioral definitions can be (and have been) greatly improved with biological data (Fox, 2018 ). In a classic example, biobehavioral data have shown that respondent processes in food aversion are enduring and do not require immediate pairing (Garcia, Kimeldorf, & Koelling, 1955 ). Biological sources of information can inform the discussion as to whether theoretically it is worthwhile to consider conditioning separate or interlocking processes (Stein, 1997 ). Maintaining the operant–respondent distinction may largely be for the sake of established procedures in applied behavior analysis and for instructional ease when introducing these concepts.

Integrating Planaria with Modern Behavior Science

Inheritance of behavioral traits.

The planarian’s regenerative powers are being investigated to defy the aging process and unlock regeneration for humans (Sahu et al., 2017 ). Planarian regeneration is also of interest as to what facilitates memory and learning. Learning to approach and eat food under aversive lighting retains after dissection to both tail and head segments (Shomrat & Levin, 2013 ). Retention of eating behavior could reflect, like taste aversion, that there is a biobehavioral interplay related to survival (Garcia et al., 1955 ). Retention of training of an arbitrary operant behavior has yet to be demonstrated. It is interesting that biologists have also noted that conditioned avoidance retains from a larva to moth, a process that is characterized by substantial morphological reorganization (Blackiston, Silva Casey, & Weiss, 2008 ). The implication is, from this and planaria research, that there are biological mechanisms for conditioning that do not require repeated experience even after such substantial morphological changes. If this is the case, it could defy many of the widely held assumptions regarding learning and inheritance (Neuhof, Levin, & Rechavi, 2016 ). In essence, it is unknown whether all neuronally encoded learning from the host is regenerated in the asexual cloning process. Neuhof et al. ( 2016 ) describe four cloning case scenarios in a hypothesis paper presented in Fig. ​ Fig.5 5 where clones resemble (1) twins with an erasure of the host memory; (2) siblings where the head section retains memories of the host but their brains were the same at some point in the planaria’s life span; (3) birth of a child where the brain is made of naïve brain tissue constituting a new generation; and a (4) clone of self and memories.

Adapted from Neuhof et al. ( 2016 )

Although, planaria naturally engage in asexual cloning in the wild, in laboratories it is possible to transplant the head of one planarian onto another planarian, where the new head will take control of a headless body (Reddien & Alvarado, 2004 ). There are only a few species that can survive a surgical procedure like a brain transplant. Successful brain transplants (defined by regaining close to normal behavior after 48 hours) have been accomplished with marine polyclad Notoplana acticola (Pagán, 2014 ). Axolotls are one of the few vertebrates that can survive such a transplantation (De Both, 1968 ), and there is evidence that avoidance responses maintain after a “trained brain” is transferred to a naïve host axolotl (Hershkowitz, Segal, & Samuel, 1972 ).

Opportunities for University Learning Labs

Conditioned place preference occurs with planaria in many scenarios. In a typical scenario, one half of a petri dish is illuminated and the other is in darkness, and the planarian is placed in the mid-section (Ramoz et al., 2012 ). Time spent and number of entrances to both sides are measured in baseline (Ramoz et al., 2012 ; Raffa, Shah, Tallarida, & Rawls, 2013 ). In general, naïve worms spend their time on the darkened side. Later, however, after the planarian is exposed to a drug while exposed to light, preference will shift to spending more time in the illuminated side of the dish (Ramoz et al., 2012 ). This demonstrates drugs can perturb the effectiveness of a stimulus as a reinforcer or punisher, and are important factors to consider within avoidance assays.

The Van Oye Maze also serves as housing, eliminating the need to handle the worms. Groups of worms can be placed in a 250 ml beaker where a baited hook is suspended in the water and gradually lowered (8 mm, 16 mm, 24 mm, and 32 mm). The percentage of worms reaching the goal are compared to control groups at the same 32 mm lowered bait level, who did not receive the gradual lowering (Wells, 1967 ). A testing condition without food, just the hook, allows differentiating between chemical gradient detection and conditioned place preference (Wells et al., 1966 ). Researchers note that this preparation still constitutes one of the most convincing evidence of operant learning due to the number of successful replications (Nicolas et al., 2008 ), and because its methodological rigor makes it challenging to reach other conclusions. The above Van Oye Maze and conditioned place preference procedure do not require expert handling or hand shaping for convincing demonstrations of training.

Many older experiments involving planaria lacked appropriate controls (Block & McConnell, 1967 ; Halas et al., 1962 ; Thompson & McConnell, 1955 ). Planaria laboratories traditionally used numerous and varied training procedures, and often relied on hand-training methods to prompt a planarian to motion, and as a result there have been numerous replication failures (Nicolas et al., 2008 ). Automated devices track behavior and eliminate experimenter bias while minimizing handling or differentials in researcher training expertise (Blackiston, Shomrat, Nicolas, Granata, & Levin, 2010 ). These devices are costly, and it is still crucial to understand functional behavioral processes when designing an experiment. In some cases, hand shaping has been successfully applied, and is cost effective compared to automated devices (Chicas-Mosier & Abramson, 2015 ). Hand shaping might even be warranted for complex behaviors that cannot be integrated into algorithms and automated. An extension of Chicas-Mosier and Abramson’s hand-shaping procedure using water (described in “Operant Responding” section) could be to yoke a control worm in an adjoined half petri dish, side by side with the experimental worm, so that all movements of the dish are experienced by both worms. In our estimation, the shaping procedure for the experimental worm requires that the dish be moved substantially. Although water access is likely the functional reinforcer, the contribution of movement to the results has not been examined.

Light is one of the most common stimuli used in the behavior training literature with planaria, and has been a preferred training stimulus by these authors. Light is considered a weaker unconditioned stimulus compared to vibration and shock (Vandeventer & Ratner, 1964 ). Researchers have examined the specific avoidance responses elicited and or evoked by differing light stimuli (Boring, 1912 ; Marriott, 1958 ; Pirenne & Marriott, 1955 ; Paskin, Jellies, Bacher, & Beane, 2014 ). In general, light will stimulate a planarian into locomotion, and they will come to rest in the dark (Boring, 1912 ), we refer to this pattern of behavior as photonegative responding.

Responsivity to light can be suppressed after an injury, eating, or if the dish contains slime trails (Riccio & Corning, 1969 ). Besides the photonegative moving away from light, planaria engage in distinct responses to light, the first being stereotypic head turns (“wig-waggling”), and the second being a longitudinal body turn, which has previously been referred to as contractions (Halas, James, & Stone, 1961 ). Eye-gouged samples engage in a similar cephalic “wig-waggling” response to light, albeit sluggishly (Taliaferro, 1920 ), and only planaria with intact eyes move away from a lateral light sources (Boring, 1912 ). Therefore, the eyes are integral to directional moving away from light but not “wig-waggling,” which potentially indicates there are photo-receptors on the body of the planaria mediating small head turns. Note planaria may have directional turn preferences, and reversing these preferences back and forth across trials is required to demonstrate effective stimulus control (Abbott & Wong, 2008 ).

Planaria are more sensitive to light on the ultraviolet side of the spectrum than infrared (Pirenne & Marriott, 1955 ). Overdoses of ultraviolet light can cause the death of planaria (Allee & Wilder, 1939 ; McConnell, 1965). Paskin et al. ( 2014 ) replicated some of this previous research by collecting data on photonegative responses measured by the distance of worms in four quadrants after 2 minutes of light exposure. They then also recording the angle of head turns away from lasers of differing wavelengths. The actual angle of the bend was greater when using ultraviolet light was than red light (Paskin et al., 2014 ). Planaria appear to be least sensitive to light in the red spectrum (Shomrat & Levin, 2013 ).

From our investigations, the use of red ambient light as illumination, with contingent omnidirectional light delivery (from the sides and vertically from the bottom), where any type of turn immediately switches off white light, has been useful for training planaria. After an initial turn training in either direction, the researcher can select a specific turn to reinforce with the removal of aversive lighting to initiate directional training. In a video included as supplementary material , the use of this device is demonstrated. In the four main panels, one single worm receives baseline (red background light), left turn training (light termination for turning left), right turn training (light termination for turning right), and omission training (light termination for not turning). The controls consist of two separate worms receiving either red light, or an automated delivery of light on for three seconds and off for seven seconds. The reason why ultraviolet light was not selected as the training stimulus is because a weak aversive stimulus should be selected with hand shaping, as otherwise accidental overexposure to a strong aversive stimulus will result in punishing the desired response beyond easy reacquisition (Hoffman & Fleshler, 1959 ).

Experimental analysis of behavior (EAB), applied behavior analysis (ABA), and clinical service delivery have been described as three interlocking domains (Moore & Cooper, 2003 ; Morris, 1992 ), and a threat to one affects the others in the long term. Although ABA and service delivery appear to be thriving (Deochand & Fuqua, 2016 ), EAB has been encountering new hurdles (Fox, 2018 ). Funding and jobs for basic research in psychology have dwindled, as have undergraduate opportunities to gain formative animal lab learning experiences (see Abramson, 2015 ). If EAB as a field is to thrive, effective strategies to conduct nonhuman research must be in place (Critchfield, 2011 ). Perhaps conducting research with new species, which can be cost-effectively maintained in a laboratory, is a solution; diversification of EAB within the higher education environment could be the “ultimate key to survival” (Poling, 2010 ). Invertebrate research may provide both professional research programs and student research laboratories with the flexibility they need to survive in the current academic climate.

Unraveling the diverse tapestry linking species to their evolutionary origins will require integrating behavioral assays among surviving members of each species. Planaria have unique morphology allowing for reconceptualizing the nature of memory from the bottom up in a biobehavioral model, and could inform what mode of conditioning may require higher brain function. Researchers within behavior science are continuing to develop innovative techniques for training planaria, which could become standard practice (Chicas-Mosier & Abramson, 2015 ). The boundaries of learning have yet to be delineated in planaria. Planaria have been known to go to the top of an electrode to avoid shock (McConnell, 1965), which is as functional a response as the rat that opted for breakfast in bed (Azrin & Holz, 1966 ). Conditioning has been suggested to be one reinforcement process, shown in two procedures (Donahoe & Palmer, 2004 ; Calvin & McDowell, 2016 ), which explains why it was challenging to distinguish between the two in the murky behavioral history of the planaria. If various behavioral assays demonstrate training can be preserved in the planaria in different segments, then these results implicate different biological processes regarding memory transference and retention.

Regeneration is dependent upon neuronal firing to amputated sections (Singer, 1952 ) and is likely essential for regaining the functionality of limbs post regeneration, but mammals may experience phantom pain after similar amputation. Phantom limb pain remains something of an enigma in psychology (Weeks, Anderson-Barnes, & Tsao, 2010 ), but mammal models only allow one amputation whereas regenerative models offer an infinite number of attempts and potential insight into such phenomena. The reliance of methodologically flawed functional magnetic resonance imaging studies may do little to advance the science and investigation into psychological phenomena even with human subjects (Fiedler, 2011 ), perhaps more will be learned from organisms like the planaria as it relates to the chemistry and physiology of learning.

In summary, many traditional nonhuman subjects are no longer as convenient to use, leading to dwindling opportunities and resources for students to engage in animal research, subverting the formative educational experiences for psychology majors (Abramson, 2015 ). Planaria are suitable for use for both training and research paradigms. Extending our reach to incorporating other animal models serves as strong evidence regarding the interspecies generality of our behavioral technology (Sidman, 1960 ). Selecting an organism based on tradition ignores Skinner’s advice to drop everything to study interesting behavioral phenomena (Skinner, 1956 ). Behavioral research with planaria is ongoing and will happen with or without our input, therefore ensuring behavioral science contributes is a “no brainer”.

Electronic Supplementary Material

(MP4 22402 kb)

Acknowledgments

The authors thank Rachel L. Burroughs for helping with editing an earlier draft of this manuscript.

Compliance with Ethical Standards

All material contained herein is not plagiarized.

The authors declare that they have no conflict of interest.

1 Two or more species were used in some studies, therefore the summed total of all the listed species is over 100%.

• Abbott SM, Wong GK. The conditioning and memory retention of planaria ( Dugesia tigrina ) for directional preferences. Bios. 2008; 79 (4):160–170. [ Google Scholar ]
• Abramson CI. A crisis in comparative psychology: Where have all the undergraduates gone? Frontiers in Psychology. 2015; 6 :1589. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Abramson CI, Feinman RD. Lever-press conditioning in the crab. Physiology & Behavior. 1990; 48 (2):267–272. [ PubMed ] [ Google Scholar ]
• Adell, T., Saló, E., van Loon, J. J., & Auletta, G. (2014). Planarians sense simulated microgravity and hypergravity. BioMed Research International , 1–10. 10.1155/2014/679672. [ PMC free article ] [ PubMed ]
• Akiyama Y, Agata K, Inoue T. Spontaneous behaviors and wall-curvature lead to apparent wall preference in planarian. PLoS One. 2015; 10 :1–17. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Allee WC, Wilder J. Group protection for Euplanaria dorotocephala from ultra-violet radiation. Physiological Zoology. 1939; 12 (2):110–135. [ Google Scholar ]
• Allen GD. Reversibility of the reactions of Planaria dorotocephala to a current of water. Biological Bulletin. 1915; 29 :111–128. [ Google Scholar ]
• American Psychological Association (APA). (2017). Resolution reaffirming support for research and teaching with nonhuman animals. Retrieved from http://www.apa.org/about/policy/animal-research-resolution.pdf .
• American Psychological Association (APA). (n.d.). Research animals in psychology. Retrieved from https://www.apa.org/research/responsible/research-animals.pdf .
• Auletta G, Adell T, Colagè I, D’Ambrosio P, Salò E. Space research program on Planarian Schmidtea Mediterranea ’s establishment of the anterior-posterior axis in altered gravity conditions. Microgravity Science and Technology. 2012; 24 :419–425. [ Google Scholar ]
• Azrin NH, Holz WC. Punishment. In: Honig WK, editor. Operant behavior: areas of research and application. East Norwalk, CT: Appleton-Century-Crofts; 1966. pp. 380–447. [ Google Scholar ]
• Barnes TC, Skinner BF. The progressive increase in the geotropic response of the ant Aphaenogaster . The Journal of General Psychology. 1930; 4 :102–112. [ Google Scholar ]
• Baxter R, Kimmel HD. Conditioning and extinction in the planarian. American Journal of Psychology. 1963; 76 :665–669. [ PubMed ] [ Google Scholar ]
• Best JB. Diurnal cycles and cannibalism in planaria. Science. 1960; 131 :1884–1885. [ PubMed ] [ Google Scholar ]
• Best JB. Behavior of planaria in instrumental learning paradigms. Animal Behaviour. 1965; 13 (Suppl. 1):69–75. [ Google Scholar ]
• Best JB, Rubinstein I. Environmental familiarity and feeding in a planarian. Science. 1962; 135 (3507):916–918. [ PubMed ] [ Google Scholar ]
• Bitterman EM. Phyletic differences in learning. American Psychologist. 1965; 20 :396–410. [ PubMed ] [ Google Scholar ]
• Blackiston D, Shomrat T, Nicolas CL, Granata C, Levin M. A second-generation device for automated training and quantitative behavior analyses of molecularly-tractable model organisms. PLoS One. 2010; 5 :1–20. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Blackiston DJ, Silva Casey E, Weiss MR. Retention of memory through metamorphosis: can a moth remember what it learned as a caterpillar? PLoS One. 2008; 3 :e1736. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Block RA, McConnell JV. Classically conditioned discrimination in the Planarian, Dugesia dorotocephala . Nature. 1967; 215 :1465–1466. [ PubMed ] [ Google Scholar ]
• Bocchinfuso DG, Taylor P, Ross E, Ignatchenko A, Ignatchenko V, Kislinger T, et al. Proteomic profiling of the planarian Schmidtea mediterranea and its mucous reveals similarities with human secretions and those predicted for parasitic flatworms. Molecular & Cellular Proteomics. 2012; 11 :681–691. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Boring EG. Notes on the negative reaction under light-adaptation in the planarian. Journal of Animal Behavior. 1912; 2 (4):229. [ Google Scholar ]
• Branch M. Malignant side effects of null-hypothesis significance testing. Theory & Psychology. 2014; 24 :256–277. [ Google Scholar ]
• Breland K, Breland M. The misbehavior of organisms. American Psychologist. 1961; 16 :681. [ Google Scholar ]
• Calvin OL, McDowell JJ. Extending unified-theory-of-reinforcement neural networks to steady-state operant behavior. Behavioral Processes. 2016; 127 :52–61. [ PubMed ] [ Google Scholar ]
• Chicas-Mosier AM, Abramson CI. A new instrumental/operant conditioning technique suitable for inquiry-based activities in courses on experimental psychology, learning, and comparative psychology using planaria ( Dugesia dorotocephala and Dugesia tigrina ) Comprehensive Psychology. 2015; 4 :1–6. [ Google Scholar ]
• Corning WC, Lahue R. Invertebrate strategies in comparative learning studies. American Zoologist. 1972; 12 :455–469. [ Google Scholar ]
• Corning WC, Riccio D. The planarian controversy. In: Bryne W, editor. Molecular approaches to learning and memory. New York, NY: Academic Press; 1970. pp. 107–150. [ Google Scholar ]
• Crawford FT, Skeen SLC. Operant responding in the planarian: a replication study. Psychological Reports. 1967; 20 :1023–1027. [ Google Scholar ]
• Critchfield TS. To a young basic scientist, about to embark on a program of translational research. The Behavior Analyst. 2011; 34 (2):137–148. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• De Both NJ. Transplantation of axolotl heads. Science. 1968; 162 :460–461. [ PubMed ] [ Google Scholar ]
• Deochand N, Fuqua RW. BACB certification trends: state of the states (1999 to 2014) Behavior Analysis in Practice. 2016; 9 :243–252. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Dexter JP, Tamme MB, Lind CH, Collins EMS. On-chip immobilization of planarians for in vivo imaging. Scientific Reports. 2014; 4 :1–9. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Dixon MR, Daar JH, Gunnarsson K, Johnson ML, Shayter AM. Stimulus preference and reinforcement effects of the Madagascar hissing cockroach ( Gromphordahina portentosa ): a case of reverse translational research. The Psychological Record. 2016; 66 :41–51. [ Google Scholar ]
• Donahoe JW, Palmer DC. Learning and complex behavior. Richmond, MA: Ledgetop Publishing; 2004. [ Google Scholar ]
• Downey P, Jahan-Parwar B. Cooling as reinforcing stimulus in Aplysia. American Zoologist. 1972; 12 :507–512. [ Google Scholar ]
• Duhaime-Ross, A. (2015, March 18). Memory in the flesh: a radical 1950’s scientist suggested memories could survive outside the brain—and he may have been right. The Verge. Retrieved August 24, 2018, from https://www.theverge.com/2015/3/18/8225321/memory-research-flatworm-cannibalism-james-mcconnell-michael-levin .
• Egger B, Gschwentner R, Rieger R. Free-living flatworms under the knife: past and present. Development Genes and Evolution. 2007; 217 :89. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Epstein R. On pigeons and people: a preliminary look at the Columban Simulation Project. The Behavior Analyst. 1981; 4 :43–55. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Fiedler K. Voodoo correlations are everywhere—not only in neuroscience. Perspectives on Psychological Science. 2011; 6 :163–171. [ PubMed ] [ Google Scholar ]
• Fox AE. The future is upon us. Behavior Analysis: Research & Practice. 2018; 18 :144–150. [ Google Scholar ]
• Garcia J, Kimeldorf DJ, Koelling RA. Conditioned aversion to saccharin resulting from exposure to gamma radiation. Science. 1955; 122 :157–158. [ PubMed ] [ Google Scholar ]
• Grossmann KE. Continuous, fixed-ratio, and fixed-interval reinforcement in honey bees. Journal of the Experimental Analysis of Behavior. 1973; 20 :105–109. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Halas ES. Operant conditioning in planaria: a criticism. Science. 1963; 141 :390–392. [ PubMed ] [ Google Scholar ]
• Halas ES, James RL, Knutson CS. An attempt at classical conditioning in the planarian. Journal of Comparative & Physiological Psychology. 1962; 55 (6):969–971. [ PubMed ] [ Google Scholar ]
• Halas ES, James RL, Stone LA. Types of responses elicited in planaria by light. Journal of Comparative & Physiological Psychology. 1961; 54 :302. [ PubMed ] [ Google Scholar ]
• Hershkowitz M, Segal M, Samuel D. The acquisition of dark avoidance by transplantation of the forebrain of trained newts ( Pleurodeles waltl ) Brain Research. 1972; 48 :366–369. [ PubMed ] [ Google Scholar ]
• Hoffman HS, Fleshler M. Aversive control with the pigeon. Journal of the Experimental Analysis of Behavior. 1959; 2 :213–218. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Jacobson AL, Horowitz SD, Fried C. Classical conditioning, pseudoconditioning, or sensitization in the planarian. Journal of Comparative & Physiological Psychology. 1967; 64 (1):73. [ PubMed ] [ Google Scholar ]
• Jenkins MM. Aspects of planarian biology and behavior. In: Corning WC, Ratner SC, editors. Chemistry of learning. New York, NY: Plenum Press; 1967. pp. 116–143. [ Google Scholar ]
• Katz AN. Inexpensive animal learning exercises for huge introductory laboratory classes. Teaching of Psychology. 1978; 5 (2):91–93. [ Google Scholar ]
• Krantz ML. Operant conditioning of planarians. Beta Beta Beta Biological Society. 1964; 35 (3):139–141. [ Google Scholar ]
• Lattal KA. The human side of animal behavior. The Behavior Analyst. 2001; 24 :147–161. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Lee RM. Conditioning of a free operant response in planaria. Science. 1963; 139 :1048–1049. [ PubMed ] [ Google Scholar ]
• Marriott FHC. The absolute light-sensitivity and spectral threshold curve of the aquatic flatworm Dendrocoelum lacteum . Journal of Physiology. 1958; 143 :369–379. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• McConnell JV. Memory transfer through cannibalism in planarians. Journal of Neuropsychiatry. 1962; 3 (1):542–548. [ Google Scholar ]
• McConnell JV. Comparative physiology: learning in invertebrates. Annual Review of Physiology. 1966; 28 :107–136. [ PubMed ] [ Google Scholar ]
• McConnell JV, editor. A manual of psychological experimentation on planarians. 2. Ann Arbor, MI: Worm Runner's Digest; 1967. [ Google Scholar ]
• McConnell JV, Jacobson AL, Kimble DP. The effects of regeneration upon retention of a conditioned response in the planarian. Journal of Comparative & Physiological Psychology. 1959; 52 :1–5. [ PubMed ] [ Google Scholar ]
• Moore J, Cooper JO. Some proposed relations among the domains of behavior analysis. The Behavior Analyst. 2003; 26 :69–84. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Morris EK. The aim, progress, and evolution of behavior analysis. The Behavior Analyst. 1992; 15 :3–29. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Neuhof M, Levin M, Rechavi O. Vertically- and horizontally-transmitted memories: the fading boundaries between regeneration and inheritance in planaria. Biology Open. 2016; 5 :1177–1188. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Newmark PA, Alvarado AS. Not your father's planarian: a classic model enters the era of functional genomics. Nature Reviews Genetics. 2002; 3 :210. [ PubMed ] [ Google Scholar ]
• Nicolas CL, Abramson CI, Levin M. Analysis of behavior in the planarian model. In: Raffa RB, Rawls SM, editors. Planaria: a model for drug action and abuse. Austin, TX: Landes Bioscience; 2008. pp. 83–94. [ Google Scholar ]
• Pagán OR. The first brain: the neuroscience of planarians. New York, NY: Oxford University Press; 2014. [ Google Scholar ]
• Pagán OR, Deats S, Baker D, Montgomery E, Wilk G, Tenaglia M, Semon J. Planarians require an intact brain to behaviorally react to cocaine, but not to react to nicotine. Neuroscience. 2013; 246 :265–270. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Paskin TR, Jellies J, Bacher J, Beane WS. Planarian phototactic assay reveals differential behavioral responses based on wavelength. PLoS One. 2014; 9 :e114708. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Pear JJ, Eldridge GD. The operant-respondent distinction: future directions. Journal of the Experimental Analysis of Behavior. 1984; 42 :453–467. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Pirenne MH, Marriott FHC. Light sensitivity of the aquatic flatworm Dendrocoelum lacteum . Nature. 1955; 175 :642. [ Google Scholar ]
• Poling A. Looking to the future: will behavior analysis survive and prosper? The Behavior Analyst. 2010; 33 :7–17. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Raffa RB, Holland LJ, Schulingkamp RJ. Quantitative assessment of dopamine D2 antagonist activity using invertebrate (Planaria) locomotion as a functional endpoint. Journal of Pharmacological and Toxicological Methods. 2001; 45 (3):223–226. [ PubMed ] [ Google Scholar ]
• Raffa RB, Shah S, Tallarida CS, Rawls SM. Amphetamine conditioned place preference in planarians. Journal of Behavioral & Brain Science. 2013; 3 :131–136. [ Google Scholar ]
• Ramm SA. Exploring the sexual diversity of flatworms: ecology, evolution, and the molecular biology of reproduction. Molecular Reproduction & Development. 2016; 84 (2):120–131. [ PubMed ] [ Google Scholar ]
• Ramoz L, Lodi S, Bhatt P, Reitz AB, Tallarida C, Tallarida RJ, et al. Mephedrone (“bath salt”) pharmacology: insights from invertebrates. Neuroscience. 2012; 208 :79–84. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Reddien PW, Alvarado AS. Fundamentals of planarian regeneration. Annual Review of Cell and Developmental Biology. 2004; 20 :725–757. [ PubMed ] [ Google Scholar ]
• Reynierse JH. Aggregation formation in planaria, Phagocata gracilis and Cura foremani : species differentiation. Animal Behaviour. 1967; 15 :270–272. [ PubMed ] [ Google Scholar ]
• Reynierse JH, Ellis RR. Aggregation formation in three species of planaria: distance to nearest neighbour. Nature. 1967; 214 :895–896. [ PubMed ] [ Google Scholar ]
• Reynierse JH, Gleason KK, Ottemann R. Mechanisms producing aggregations in planaria. Animal Behaviour. 1969; 17 :47–63. [ Google Scholar ]
• Reynoldson TB, Young JO. The food of four species of lake-dwelling triclads. Journal of Animal Ecology. 1963; 32 :175–191. [ Google Scholar ]
• Riccio D, Corning WC. Slime and planarian behavior. The Psychological Record. 1969; 19 :507–513. [ Google Scholar ]
• Rilling M. The mystery of the vanished citations: James McConnell’s forgotten 1960s quest for planarian learning, a biochemical engram, and celebrity. American Psychologist. 1996; 51 :589–598. [ Google Scholar ]
• Sahu S, Dattani A, Aboobaker AA. Secrets from immortal worms: what can we learn about biological ageing from the planarian model system? Seminars in Cell & Developmental Biology. 2017; 70 :108–121. [ PubMed ] [ Google Scholar ]
• Shomrat T, Levin M. An automated training paradigm reveals long-term memory in planarians and its persistence through head regeneration. Journal of Experimental Biology. 2013; 216 :3799–3810. [ PubMed ] [ Google Scholar ]
• Sidman M. Tactics of scientific research. New York, NY: Basic Books; 1960. [ Google Scholar ]
• Singer M. The influence of the nerve in regeneration of the amphibian extremity. Quarterly Review of Biology. 1952; 27 :169–200. [ PubMed ] [ Google Scholar ]
• Skinner BF. A case history in scientific method. American Psychologist. 1956; 11 (5):221. [ Google Scholar ]
• Skinner BF. The phylogeny and ontogeny of behavior. Science. 1966; 153 :1205–1213. [ PubMed ] [ Google Scholar ]
• Smalheiser NR, Manev H, Costa E. RNAi and brain function: was McConnell on the right track? Trends in Neurosciences. 2001; 24 :216–218. [ PubMed ] [ Google Scholar ]
• Sokolowski MBC, Disma G, Abramson CI. A paradigm for operant conditioning of blow flies ( Phorma terrae novae robineau-desvoidy , 1830) Journal of the Experimental Analysis of Behavior. 2010; 93 :81–89. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Stein L. Biological substrates of operant conditioning and the operant-respondent distinction. Journal of the Experimental Analysis of Behavior. 1997; 67 :246–253. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Stevenson CG, Beane WS. A low percent ethanol method for immobilizing planarians. PLoS One. 2010; 5 :1–12. [ PMC free article ] [ PubMed ] [ Google Scholar ]
• Talbot J, Schötz EM. Quantitative characterization of planarian wild-type behavior as a platform for screening locomotion phenotypes. Journal of Experimental Biology. 2011; 214 :1063–1067. [ PubMed ] [ Google Scholar ]
• Taliaferro WH. Reactions to light in Planaria maculata , with special reference to the function and structure of the eyes. Journal of Experimental Zoology. 1920; 31 :58–116. [ Google Scholar ]
• Thompson R, McConnell JV. Classical conditioning in planarian, Dugesia dorotocephala . Journal of Comparative and Physiological Psychology. 1955; 48 :65–68. [ PubMed ] [ Google Scholar ]
• Travis GD. Replicating replication? Aspects of the social construction of learning in planarian worms. Social Studies of Science. 1981; 11 :11–32. [ Google Scholar ]
• Vandeventer JM, Ratner SC. Variables affecting the frequency of response of planaria to light. Journal of Comparative & Physiological Psychology. 1964; 57 :407–411. [ PubMed ] [ Google Scholar ]
• Walker DR. Memory transfer in planarians: an artifact of the experimental variables. Psychonomic Science. 1966; 5 :357–358. [ Google Scholar ]
• Walker DR, Milton GA. Memory transfer vs. sensitization in cannibal planarians. Psychonomic Science. 1966; 5 :293–294. [ Google Scholar ]
• Weeks SR, Anderson-Barnes VC, Tsao JW. Phantom limb pain: theories and therapies. The Neurologist. 2010; 16 :277–286. [ PubMed ] [ Google Scholar ]
• Wells PH. Training flatworms in a Van Oye maze. In: Corning WC, Ratner SC, editors. Chemistry of learning. New York, NY: Plenum Press; 1967. pp. 251–254. [ Google Scholar ]
• Wells PH, Jennings LB, Davis M. Conditioning planarian worms in a van Oye type maze. American Zoologist. 1966; 6 (3):295. [ Google Scholar ]
• Zimmermann Z, Watkins E, Poling A. JEAB research over time: species used, experimental designs, statistical analyses, and sex of subjects. The Behavior Analyst. 2015; 38 :203–218. [ PMC free article ] [ PubMed ] [ Google Scholar ]

Behavioral Research with Planaria

• Learning: No Brain Required
• Published: 09 November 2018
• Volume 41 , pages 447–464, ( 2018 )

Cite this article

• Neil Deochand   ORCID: orcid.org/0000-0001-8163-2285 1 ,
• Mack S. Costello   ORCID: orcid.org/0000-0002-9613-7647 2 &
• Michelle E. Deochand 3  

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This article serves as a brief primer on planaria for behavior scientists. In the 1950s and 1960s, McConnell’s planarian laboratory posited that conditioned behavior could transfer after regeneration, and through cannibalization of trained planaria. These studies, the responses, and replications have been collectively referred to as the “planarian controversy.” Successful behavioral assays still require refinement with this organism, but they could add valuable insight into our conceptualization of memory and learning. We discuss how the planarian’s distinctive biology enables an examination of biobehavioral interaction models, and what behavior scientists must consider if they are to advance behavioral research with this organism. Suggestions for academics interested in building planaria learning laboratories are offered.

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Two or more species were used in some studies, therefore the summed total of all the listed species is over 100%.

Abbott, S. M., & Wong, G. K. (2008). The conditioning and memory retention of planaria ( Dugesia tigrina ) for directional preferences. Bios, 79 (4), 160–170.

Article   Google Scholar  

Abramson, C. I. (2015). A crisis in comparative psychology: Where have all the undergraduates gone? Frontiers in Psychology, 6 , 1589. https://doi.org/10.3389/fpsyg.2015.01500 .

Abramson, C. I., & Feinman, R. D. (1990). Lever-press conditioning in the crab. Physiology & Behavior, 48 (2), 267–272.

Adell, T., Saló, E., van Loon, J. J., & Auletta, G. (2014). Planarians sense simulated microgravity and hypergravity. BioMed Research International , 1–10. https://doi.org/10.1155/2014/679672 .

Akiyama, Y., Agata, K., & Inoue, T. (2015). Spontaneous behaviors and wall-curvature lead to apparent wall preference in planarian. PLoS One, 10 , 1–17. https://doi.org/10.1371/journal.pone.0142214 .

Allee, W. C., & Wilder, J. (1939). Group protection for Euplanaria dorotocephala from ultra-violet radiation. Physiological Zoology, 12 (2), 110–135. https://doi.org/10.1086/physzool.12.2.30151489 .

Allen, G. D. (1915). Reversibility of the reactions of Planaria dorotocephala to a current of water. Biological Bulletin, 29 , 111–128. https://doi.org/10.2307/1536302 .

American Psychological Association (APA). (2017). Resolution reaffirming support for research and teaching with nonhuman animals. Retrieved from http://www.apa.org/about/policy/animal-research-resolution.pdf .

American Psychological Association (APA). (n.d.). Research animals in psychology. Retrieved from https://www.apa.org/research/responsible/research-animals.pdf .

Auletta, G., Adell, T., Colagè, I., D’Ambrosio, P., & Salò, E. (2012). Space research program on Planarian Schmidtea Mediterranea ’s establishment of the anterior-posterior axis in altered gravity conditions. Microgravity Science and Technology, 24 , 419–425. https://doi.org/10.1007/s12217-012-9317-6 .

Azrin, N. H., & Holz, W. C. (1966). Punishment. In W. K. Honig (Ed.), Operant behavior: areas of research and application (pp. 380–447). East Norwalk, CT: Appleton-Century-Crofts.

Google Scholar  

Barnes, T. C., & Skinner, B. F. (1930). The progressive increase in the geotropic response of the ant Aphaenogaster . The Journal of General Psychology, 4 , 102–112.

Baxter, R., & Kimmel, H. D. (1963). Conditioning and extinction in the planarian. American Journal of Psychology, 76 , 665–669. https://doi.org/10.2307/1419718 .

Article   PubMed   Google Scholar  

Best, J. B. (1960). Diurnal cycles and cannibalism in planaria. Science, 131 , 1884–1885. https://doi.org/10.1126/science.131.3417.1884 .

Best, J. B. (1965). Behavior of planaria in instrumental learning paradigms. Animal Behaviour, 13 (Suppl. 1), 69–75.

Best, J. B., & Rubinstein, I. (1962). Environmental familiarity and feeding in a planarian. Science, 135 (3507), 916–918.

Bitterman, E. M. (1965). Phyletic differences in learning. American Psychologist, 20 , 396–410. https://doi.org/10.1037/h0022328 .

Blackiston, D., Shomrat, T., Nicolas, C. L., Granata, C., & Levin, M. (2010). A second-generation device for automated training and quantitative behavior analyses of molecularly-tractable model organisms. PLoS One, 5 , 1–20. https://doi.org/10.1371/journal.pone.0014370 .

Blackiston, D. J., Silva Casey, E., & Weiss, M. R. (2008). Retention of memory through metamorphosis: can a moth remember what it learned as a caterpillar? PLoS One, 3 , e1736. https://doi.org/10.1371/journal.pone.0001736 .

Article   PubMed   PubMed Central   Google Scholar  

Block, R. A., & McConnell, J. V. (1967). Classically conditioned discrimination in the Planarian, Dugesia dorotocephala . Nature, 215 , 1465–1466.

Bocchinfuso, D. G., Taylor, P., Ross, E., Ignatchenko, A., Ignatchenko, V., Kislinger, T., et al. (2012). Proteomic profiling of the planarian Schmidtea mediterranea and its mucous reveals similarities with human secretions and those predicted for parasitic flatworms. Molecular & Cellular Proteomics, 11 , 681–691. https://doi.org/10.1074/mcp.M112.019026 .

Boring, E. G. (1912). Notes on the negative reaction under light-adaptation in the planarian. Journal of Animal Behavior, 2 (4), 229. https://doi.org/10.1037/h0075688 .

Branch, M. (2014). Malignant side effects of null-hypothesis significance testing. Theory & Psychology, 24 , 256–277. https://doi.org/10.1177/0959354314525282 .

Breland, K., & Breland, M. (1961). The misbehavior of organisms. American Psychologist, 16 , 681. https://doi.org/10.1037/h0040090 .

Calvin, O. L., & McDowell, J. J. (2016). Extending unified-theory-of-reinforcement neural networks to steady-state operant behavior. Behavioral Processes, 127 , 52–61. https://doi.org/10.1016/j.beproc.2016.03.016 .

Chicas-Mosier, A. M., & Abramson, C. I. (2015). A new instrumental/operant conditioning technique suitable for inquiry-based activities in courses on experimental psychology, learning, and comparative psychology using planaria ( Dugesia dorotocephala and Dugesia tigrina ). Comprehensive Psychology, 4 , 1–6. https://doi.org/10.2466/09.IT.4.6 .

Corning, W. C., & Lahue, R. (1972). Invertebrate strategies in comparative learning studies. American Zoologist, 12 , 455–469. https://doi.org/10.1093/icb/12.3.455 .

Corning, W. C., & Riccio, D. (1970). The planarian controversy. In W. Bryne (Ed.), Molecular approaches to learning and memory (pp. 107–150). New York, NY: Academic Press.

Crawford, F. T., & Skeen, S. L. C. (1967). Operant responding in the planarian: a replication study. Psychological Reports, 20 , 1023–1027. https://doi.org/10.2466/pr0.1967.20.3c.1023 .

Critchfield, T. S. (2011). To a young basic scientist, about to embark on a program of translational research. The Behavior Analyst, 34 (2), 137–148.

De Both, N. J. (1968). Transplantation of axolotl heads. Science, 162 , 460–461. https://doi.org/10.1126/science.162.3852.460 .

Deochand, N., & Fuqua, R. W. (2016). BACB certification trends: state of the states (1999 to 2014). Behavior Analysis in Practice, 9 , 243–252. https://doi.org/10.1007/s40617-016-0118-z .

Dexter, J. P., Tamme, M. B., Lind, C. H., & Collins, E. M. S. (2014). On-chip immobilization of planarians for in vivo imaging. Scientific Reports, 4 , 1–9. https://doi.org/10.1038/srep06388 .

Dixon, M. R., Daar, J. H., Gunnarsson, K., Johnson, M. L., & Shayter, A. M. (2016). Stimulus preference and reinforcement effects of the Madagascar hissing cockroach ( Gromphordahina portentosa ): a case of reverse translational research. The Psychological Record, 66 , 41–51. https://doi.org/10.1007/s40732-015-0149-9 .

Donahoe, J. W., & Palmer, D. C. (2004). Learning and complex behavior . Richmond, MA: Ledgetop Publishing.

Downey, P., & Jahan-Parwar, B. (1972). Cooling as reinforcing stimulus in Aplysia. American Zoologist, 12 , 507–512. https://doi.org/10.1093/icb/12.3.507 .

Duhaime-Ross, A. (2015, March 18). Memory in the flesh: a radical 1950’s scientist suggested memories could survive outside the brain—and he may have been right. The Verge. Retrieved August 24, 2018, from https://www.theverge.com/2015/3/18/8225321/memory-research-flatworm-cannibalism-james-mcconnell-michael-levin .

Egger, B., Gschwentner, R., & Rieger, R. (2007). Free-living flatworms under the knife: past and present. Development Genes and Evolution, 217 , 89. https://doi.org/10.1007/s00427-006-0120-5 .

Epstein, R. (1981). On pigeons and people: a preliminary look at the Columban Simulation Project. The Behavior Analyst, 4 , 43–55. https://doi.org/10.1007/BF03391851 .

Fiedler, K. (2011). Voodoo correlations are everywhere—not only in neuroscience. Perspectives on Psychological Science, 6 , 163–171. https://doi.org/10.1177/1745691611400237 .

Fox, A. E. (2018). The future is upon us. Behavior Analysis: Research & Practice, 18 , 144–150. https://doi.org/10.1037/bar0000106 .

Garcia, J., Kimeldorf, D. J., & Koelling, R. A. (1955). Conditioned aversion to saccharin resulting from exposure to gamma radiation. Science, 122 , 157–158. https://doi.org/10.1126/science.122.3179.1089 .

Grossmann, K. E. (1973). Continuous, fixed-ratio, and fixed-interval reinforcement in honey bees. Journal of the Experimental Analysis of Behavior, 20 , 105–109. https://doi.org/10.1901/jeab.1973.20-105 .

Halas, E. S. (1963). Operant conditioning in planaria: a criticism. Science, 141 , 390–392. https://doi.org/10.1126/science.141.3579.390-a .

Halas, E. S., James, R. L., & Knutson, C. S. (1962). An attempt at classical conditioning in the planarian. Journal of Comparative & Physiological Psychology, 55 (6), 969–971. https://doi.org/10.1037/h0040092 .

Halas, E. S., James, R. L., & Stone, L. A. (1961). Types of responses elicited in planaria by light. Journal of Comparative & Physiological Psychology, 54 , 302. https://doi.org/10.1037/h0045739 .

Hershkowitz, M., Segal, M., & Samuel, D. (1972). The acquisition of dark avoidance by transplantation of the forebrain of trained newts ( Pleurodeles waltl ). Brain Research, 48 , 366–369.

Hoffman, H. S., & Fleshler, M. (1959). Aversive control with the pigeon. Journal of the Experimental Analysis of Behavior, 2 , 213–218. https://doi.org/10.1901/jeab.1959.2-213 .

Jacobson, A. L., Horowitz, S. D., & Fried, C. (1967). Classical conditioning, pseudoconditioning, or sensitization in the planarian. Journal of Comparative & Physiological Psychology, 64 (1), 73.

Jenkins, M. M. (1967). Aspects of planarian biology and behavior. In W. C. Corning & S. C. Ratner (Eds.), Chemistry of learning (pp. 116–143). New York, NY: Plenum Press.

Chapter   Google Scholar  

Katz, A. N. (1978). Inexpensive animal learning exercises for huge introductory laboratory classes. Teaching of Psychology, 5 (2), 91–93. https://doi.org/10.1207/s15328023top0502_9 .

Krantz, M. L. (1964). Operant conditioning of planarians. Beta Beta Beta Biological Society, 35 (3), 139–141.

Lattal, K. A. (2001). The human side of animal behavior. The Behavior Analyst, 24 , 147–161. https://doi.org/10.1007/BF03392026 .

Lee, R. M. (1963). Conditioning of a free operant response in planaria. Science, 139 , 1048–1049. https://doi.org/10.1126/science.139.3559.1048 .

Marriott, F. H. C. (1958). The absolute light-sensitivity and spectral threshold curve of the aquatic flatworm Dendrocoelum lacteum . Journal of Physiology, 143 , 369–379. https://doi.org/10.1113/jphysiol.1958.sp006065 .

McConnell, J. V. (1962). Memory transfer through cannibalism in planarians. Journal of Neuropsychiatry, 3 (1), 542–548.

McConnell, J. V. (1966). Comparative physiology: learning in invertebrates. Annual Review of Physiology, 28 , 107–136. https://doi.org/10.1146/annurev.ph.28.030166.000543 .

McConnell, J. V. (Ed.). (1967). A manual of psychological experimentation on planarians (2nd ed.). Ann Arbor, MI: Worm Runner's Digest.

McConnell, J. V., Jacobson, A. L., & Kimble, D. P. (1959). The effects of regeneration upon retention of a conditioned response in the planarian. Journal of Comparative & Physiological Psychology, 52 , 1–5. https://doi.org/10.1037/h0048028 .

Moore, J., & Cooper, J. O. (2003). Some proposed relations among the domains of behavior analysis. The Behavior Analyst, 26 , 69–84. https://doi.org/10.1007/BF03392068 .

Morris, E. K. (1992). The aim, progress, and evolution of behavior analysis. The Behavior Analyst, 15 , 3–29. https://doi.org/10.1007/BF03392582 .

Neuhof, M., Levin, M., & Rechavi, O. (2016). Vertically- and horizontally-transmitted memories: the fading boundaries between regeneration and inheritance in planaria. Biology Open, 5 , 1177–1188. https://doi.org/10.1242/bio.020149 .

Newmark, P. A., & Alvarado, A. S. (2002). Not your father's planarian: a classic model enters the era of functional genomics. Nature Reviews Genetics, 3 , 210. https://doi.org/10.1038/nrg759 .

Nicolas, C. L., Abramson, C. I., & Levin, M. (2008). Analysis of behavior in the planarian model. In R. B. Raffa & S. M. Rawls (Eds.), Planaria: a model for drug action and abuse (pp. 83–94). Austin, TX: Landes Bioscience.

Pagán, O. R. (2014). The first brain: the neuroscience of planarians . New York, NY: Oxford University Press.

Pagán, O. R., Deats, S., Baker, D., Montgomery, E., Wilk, G., Tenaglia, M., & Semon, J. (2013). Planarians require an intact brain to behaviorally react to cocaine, but not to react to nicotine. Neuroscience, 246 , 265–270. https://doi.org/10.1016/j.neuroscience.2013.05.010 .

Paskin, T. R., Jellies, J., Bacher, J., & Beane, W. S. (2014). Planarian phototactic assay reveals differential behavioral responses based on wavelength. PLoS One, 9 , e114708. https://doi.org/10.1371/journal.pone.0114708 .

Pear, J. J., & Eldridge, G. D. (1984). The operant-respondent distinction: future directions. Journal of the Experimental Analysis of Behavior, 42 , 453–467. https://doi.org/10.1901/jeab.1984.42-453 .

Pirenne, M. H., & Marriott, F. H. C. (1955). Light sensitivity of the aquatic flatworm Dendrocoelum lacteum . Nature, 175 , 642. https://doi.org/10.1038/175642a0 .

Poling, A. (2010). Looking to the future: will behavior analysis survive and prosper? The Behavior Analyst, 33 , 7–17. https://doi.org/10.1007/BF03392200 .

Raffa, R. B., Holland, L. J., & Schulingkamp, R. J. (2001). Quantitative assessment of dopamine D2 antagonist activity using invertebrate (Planaria) locomotion as a functional endpoint. Journal of Pharmacological and Toxicological Methods, 45 (3), 223–226.

Raffa, R. B., Shah, S., Tallarida, C. S., & Rawls, S. M. (2013). Amphetamine conditioned place preference in planarians. Journal of Behavioral & Brain Science, 3 , 131–136. https://doi.org/10.4236/jbbs.2013.31012 .

Ramm, S. A. (2016). Exploring the sexual diversity of flatworms: ecology, evolution, and the molecular biology of reproduction. Molecular Reproduction & Development, 84 (2), 120–131. https://doi.org/10.1002/mrd.22669 .

Ramoz, L., Lodi, S., Bhatt, P., Reitz, A. B., Tallarida, C., Tallarida, R. J., et al. (2012). Mephedrone (“bath salt”) pharmacology: insights from invertebrates. Neuroscience, 208 , 79–84. https://doi.org/10.1016/j.neuroscience.2012.01.019 .

Reddien, P. W., & Alvarado, A. S. (2004). Fundamentals of planarian regeneration. Annual Review of Cell and Developmental Biology, 20 , 725–757. https://doi.org/10.1146/annurev.cellbio.20.010403.095114 .

Reynierse, J. H. (1967). Aggregation formation in planaria, Phagocata gracilis and Cura foremani : species differentiation. Animal Behaviour, 15 , 270–272. https://doi.org/10.1016/0003-3472(67)90011-5 .

Reynierse, J. H., & Ellis, R. R. (1967). Aggregation formation in three species of planaria: distance to nearest neighbour. Nature, 214 , 895–896. https://doi.org/10.1038/214895a0 .

Reynierse, J. H., Gleason, K. K., & Ottemann, R. (1969). Mechanisms producing aggregations in planaria. Animal Behaviour, 17 , 47–63. https://doi.org/10.1016/0003-3472(69)90112-2 .

Reynoldson, T. B., & Young, J. O. (1963). The food of four species of lake-dwelling triclads. Journal of Animal Ecology, 32 , 175–191. https://doi.org/10.2307/2533 .

Riccio, D., & Corning, W. C. (1969). Slime and planarian behavior. The Psychological Record, 19 , 507–513. https://doi.org/10.1007/BF03393880 .

Rilling, M. (1996). The mystery of the vanished citations: James McConnell’s forgotten 1960s quest for planarian learning, a biochemical engram, and celebrity. American Psychologist, 51 , 589–598. https://doi.org/10.1037/0003-066X.51.10.1039 .

Sahu, S., Dattani, A., & Aboobaker, A. A. (2017). Secrets from immortal worms: what can we learn about biological ageing from the planarian model system? Seminars in Cell & Developmental Biology, 70 , 108–121. https://doi.org/10.1016/j.semcdb.2017.08.028 .

Shomrat, T., & Levin, M. (2013). An automated training paradigm reveals long-term memory in planarians and its persistence through head regeneration. Journal of Experimental Biology, 216 , 3799–3810. https://doi.org/10.1242/jeb.087809 .

Sidman, M. (1960). Tactics of scientific research . New York, NY: Basic Books.

Singer, M. (1952). The influence of the nerve in regeneration of the amphibian extremity. Quarterly Review of Biology, 27 , 169–200. https://doi.org/10.1086/398873 .

Skinner, B. F. (1956). A case history in scientific method. American Psychologist, 11 (5), 221. https://doi.org/10.1037/h0047662 .

Skinner, B. F. (1966). The phylogeny and ontogeny of behavior. Science, 153 , 1205–1213.

Smalheiser, N. R., Manev, H., & Costa, E. (2001). RNAi and brain function: was McConnell on the right track? Trends in Neurosciences, 24 , 216–218. https://doi.org/10.1016/S0166-2236(00)01739-2 .

Sokolowski, M. B. C., Disma, G., & Abramson, C. I. (2010). A paradigm for operant conditioning of blow flies ( Phorma terrae novae robineau-desvoidy , 1830). Journal of the Experimental Analysis of Behavior, 93 , 81–89. https://doi.org/10.1901/jeab.2010.93-81 .

Stein, L. (1997). Biological substrates of operant conditioning and the operant-respondent distinction. Journal of the Experimental Analysis of Behavior, 67 , 246–253. https://doi.org/10.1901/jeab.1997.67-246 .

Stevenson, C. G., & Beane, W. S. (2010). A low percent ethanol method for immobilizing planarians. PLoS One, 5 , 1–12. https://doi.org/10.1371/journal.pone.0015310 .

Talbot, J., & Schötz, E. M. (2011). Quantitative characterization of planarian wild-type behavior as a platform for screening locomotion phenotypes. Journal of Experimental Biology, 214 , 1063–1067. https://doi.org/10.1242/jeb.052290 .

Taliaferro, W. H. (1920). Reactions to light in Planaria maculata , with special reference to the function and structure of the eyes. Journal of Experimental Zoology, 31 , 58–116. https://doi.org/10.1002/jez.1400310103 .

Thompson, R., & McConnell, J. V. (1955). Classical conditioning in planarian, Dugesia dorotocephala . Journal of Comparative and Physiological Psychology, 48 , 65–68. https://doi.org/10.1037/h0041147 .

Travis, G. D. (1981). Replicating replication? Aspects of the social construction of learning in planarian worms. Social Studies of Science, 11 , 11–32. https://doi.org/10.1177/030631278101100102 .

Vandeventer, J. M., & Ratner, S. C. (1964). Variables affecting the frequency of response of planaria to light. Journal of Comparative & Physiological Psychology, 57 , 407–411. https://doi.org/10.1037/h0042776 .

Walker, D. R. (1966). Memory transfer in planarians: an artifact of the experimental variables. Psychonomic Science, 5 , 357–358. https://doi.org/10.3758/BF03328401 .

Walker, D. R., & Milton, G. A. (1966). Memory transfer vs. sensitization in cannibal planarians. Psychonomic Science, 5 , 293–294. https://doi.org/10.3758/BF03328437 .

Weeks, S. R., Anderson-Barnes, V. C., & Tsao, J. W. (2010). Phantom limb pain: theories and therapies. The Neurologist, 16 , 277–286. https://doi.org/10.1097/NRL.0b013e3181edf128 .

Wells, P. H. (1967). Training flatworms in a Van Oye maze. In W. C. Corning & S. C. Ratner (Eds.), Chemistry of learning (pp. 251–254). New York, NY: Plenum Press.

Wells, P. H., Jennings, L. B., & Davis, M. (1966). Conditioning planarian worms in a van Oye type maze. American Zoologist, 6 (3), 295.

Zimmermann, Z., Watkins, E., & Poling, A. (2015). JEAB research over time: species used, experimental designs, statistical analyses, and sex of subjects. The Behavior Analyst, 38 , 203–218. https://doi.org/10.1007/s40614-015-0034-5 .

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Deochand, N., Costello, M.S. & Deochand, M.E. Behavioral Research with Planaria. Perspect Behav Sci 41 , 447–464 (2018). https://doi.org/10.1007/s40614-018-00176-w

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Behavioral Research with Planaria

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• 1 1Health and Human Services Department, University of Cincinnati, 450H Teachers-Dyer Complex, Cincinnati, OH 45221 USA.
• 2 2Department of Psychology, Rider University, 2083 Lawrenceville Road, Lawrenceville, NJ 08648 USA.
• 3 Cincinnati, OH USA.
• PMID: 31976405
• PMCID: PMC6701699
• DOI: 10.1007/s40614-018-00176-w

This article serves as a brief primer on planaria for behavior scientists. In the 1950s and 1960s, McConnell's planarian laboratory posited that conditioned behavior could transfer after regeneration, and through cannibalization of trained planaria. These studies, the responses, and replications have been collectively referred to as the "planarian controversy." Successful behavioral assays still require refinement with this organism, but they could add valuable insight into our conceptualization of memory and learning. We discuss how the planarian's distinctive biology enables an examination of biobehavioral interaction models, and what behavior scientists must consider if they are to advance behavioral research with this organism. Suggestions for academics interested in building planaria learning laboratories are offered.

Keywords: Behavior analysis; Conditioning; Invertebrate learning; Memory; Planaria.

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Conflict of InterestThe authors declare that they have no conflict of interest.

Simplified anatomical depiction of the…

Simplified anatomical depiction of the planarian CNS. The anterior contains the head, brain…

A1 depicts a single 10…

A1 depicts a single 10 mm planarian ( S. mediterranea ) at 12x…

Percentage of turns and contractions…

Percentage of turns and contractions of control and conditioned worms. Adapted from Thompson…

Percentage of turns and contractions of control and conditioned worms. Adapted from Halas…

Adapted from Neuhof et al.…

Adapted from Neuhof et al. (2016)

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Image of the week

Figure 1 | Australian green and golden bell frogs ( Ranoidea aurea ).  Waddle et al . constructed mini saunas using bricks inside a small plastic greenhouse. The warm environment enabled the frogs to clear a deadly fungal infection, and the animals gained resistance to reinfection by the fungus. Credit: Anthony Waddle

These endangered green and golden bell frogs ( Ranoidea aurea ) are relaxing in a mini sauna, a pile of bricks inside a cheap plastic greenhouse. The heat helps the animals to recover from chytridiomycosis, a deadly fungal disease that has been wiping out amphibian populations around the world. ( Nature | 6 min read , paywall)

QUOTE OF THE DAY

“you should be careful when you step into their world.”.

Nobel-prizewinning chemist Morten Meldal says that older researchers can learn important lessons about diversity from younger generations. ( Nature | 10 min read )

doi: https://doi.org/10.1038/d41586-024-02148-4

Out of all the ferocious predators out there, why do bears seem so cute and cuddly? Maybe it’s because their fluffy round ears and big nose remind us of dogs . Or maybe it’s their human-like appearance, as evidenced by a viral video of a sun bear that people thought was a person in a costume.

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Sols 4229-4231: More Analyses of the Mammoth Lakes 2 Sample!

Earth Planning Date: Friday, June 28, 2024

After reviewing results from the Evolved Gas Analysis (EGA) experiment that were downlinked yesterday afternoon ( Sols 4226-4228: A Powerful Balancing Act ), the SAM team decided they’d like to go ahead with a second experiment to analyze the Mammoth Lakes 2 drilled sample. This experiment is known as the Gas Chromatograph/Mass Spectrometer (GCMS) experiment.

SAM, whose full name is Sample Analysis at Mars, is actually a suite of three different analytical instruments that are used to measure the composition of gases which come off drilled samples as we bake them in SAM’s ovens. The three analytical instruments are called a gas chromatograph, quadrupole mass spectrometer, and tunable laser spectrometer. Each one is particularly suited for measuring specific kinds of compounds in the gases, and these include things like water, methane, carbon, or organic (carbon-containing) molecules. In the EGA experiment that we ran in our last plan, we baked the Mammoth Lakes 2 sample and measured the gas compositions using the tunable laser spectrometer and quadrupole mass spectrometer. In this plan, we’ll deliver a new pinch of sample to the SAM oven and then measure the composition of the gases that are released using the gas chromatograph and quadrupole mass spectrometer. By running both experiments, we’ll have a more thorough understanding of the materials that are in this rock.

The SAM GCMS experiment takes a lot of power to run, so it will be the focus of today’s three-sol plan. However, we still managed to fit in some other science activities around the experiment, including a ChemCam RMI mosaic of some far-off ridges, a ChemCam LIBS observation of a nodular target named “Trail Lakes,” environmental monitoring activities, and a couple Mastcam mosaics to continue imaging the terrain around the rover. Should be another fun weekend of science in Gale crater!

Written by Abigail Fraeman, Planetary Geologist at NASA's Jet Propulsion Laboratory

Related Terms

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Sols 4226-4228: A Powerful Balancing Act

Interesting Rock Textures Galore at Bright Angel

Sol 4225: Sliding Down Horsetail Falls

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Chemical Science

Simultaneous reaction- and analytical model building using dynamic flow experiments to accelerate process development.

In modern pharmaceutical research, the demand for expeditious development of synthetic routes to active pharmaceutical ingredients (APIs) has led to a paradigm shift towards data-rich process development. Conventional methodologies encompass prolonged timelines for reaction and analytical model developments. Both method developments are separated into different departments and often require an iterative process to optimize the models. Addressing this issue, we introduce an innovative dual modeling approach, integrating the development of a Process Analytical Technology (PAT) strategy with reaction optimization. This integrated approach is exemplified in diverse amidation reactions and the synthesis of the API benznidazole. The platform, characterized by a high degree of automation and minimal operator involvement, achieves PAT calibration through a “standard addition” approach. Dynamic experiments are executed to screen a broad process space and gather data for fitting kinetic parameters. Employing an open-source software program facilitates rapid kinetic parameter fitting and in silico optimization within minutes. This highly automated workflow not only expedites the understanding and optimization of chemical processes, but also holds significant promise for time and resource savings within the pharmaceutical industry.

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P. Sagmeister, L. Melnizky, J. Williams and C. O. Kappe, Chem. Sci. , 2024, Accepted Manuscript , DOI: 10.1039/D4SC01703J

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