Visual display by male fighting fish. Fish06.gif (8349084 bytes)

NOTE: A version of this lab that also includes the effects of hormones on behavior is found here.

INTRODUCTION

Ethology is the zoological study of animal behavior. Ethologists are generally interested in innate or instinctive responses ( genetically-programmed behaviors with little or no learned component). There are several advantages of instincts over learning. The animal does not require experience to perform the behavior; this is especially important if the initial response of the animal is vital to survival. Secondly, instincts do not require extensive neural coding for information storage and modification (and is therefore appropriate for animals with simple nervous systems). As an example, orb-weaving spiders build a perfect web on their first attempt (despite having no prior experience with webs for most species). Not to build a web, or to take the time learning to modify an imperfect web would result in starvation since spiders require webs to capture prey. A major cost of instincts over learning is their inflexibility in the face of environmental change. Innate responses control to one degree or another the feeding, sexual, and social behaviors of all animals (including man). For many animals these mechanisms drive them to choose a particular habitat or food. The study of communication is one of the more interesting aspects of animal behavior. Although much of our own language depends on learned responses, most organisms rely instead on genetically-coded rules of grammar and vocabulary. Three major forms of communication have been described among animals: chemical, visual, and mechanical (including touch and communication by sounds or vibrations). Of these three methods, transmitting messages by chemicals is probably the most primitive.

MATERIALS NEEDED:

Several terms are commonly used in the ethological literature to describe the behavior patterns of animals. Fixed action patterns are genetically-determined sequences of movement. These stereotyped behaviors vary little from one individual to another and are often species-specific. Releasers are found in the environment external and send out stimuli that release fixed action patterns. In the previous experiment, the courtship behavior displayed by your male roaches varied little from one male to another and represents a fixed action pattern. The pheromone deposited by the female roaches was the releaser for the males' courtship display. Releasers can be more complex than the simple presence or absence of a chemical as in the above example. In this exercise, we will explore the combination of complex visual stimuli that serve as releasers to trigger the fixed action pattern of aggressive (agonistic) display by male Siamese fighting fish (Betta splendens). The exchange of aggressive signals allows the fish to set up dominance-subordinate relationships. If the two combatants are not confined to a single bowl, the subordinate animal can flee and the conflict is resolved without the danger of bloodshed. As you shall see, visual communication is an effective way of showing varying levels of motivation and is an example of a graded response.

 
Low-level Aggression by Male Betta splendens A movie is here


High-level aggression by male Betta splendens
Movie of transition from low-level aggression (alert) to high-level aggression (here) 


Appendages used during an aggressive display by male Betta splendens.

PROCEDURE:

CAUTION: Students with brightly-patterned clothing may excite some male fighting fish. Put on a lab coat or smock to hide these colors from the fish during the experiment.

  1. Work in groups of two or three. Collect the following materials: a male fighting fish, several wooden applicator sticks, transparent tape, a mirror, scissors and construction paper. Do not position your fish where it can see neighboring animals. Avoid abrupt movements when near the fish and speak quietly. Do not tap on the side of the fish bowl.
  2. Response of Male Siamese Fighting Fish to Mirror Stimulation. Male fighting fish vary in their aggressive response and the best results will be from the more aggressive males. For aggressive animals, mirror stimulation is enough to elicit an agonistic display. To assay the relative aggressiveness of your animal and to demonstrate the behaviors associated with agonistic display, slowly move a mirror to the flat side of the bowl and observe the response of the fish to its own reflection. Do not hold the mirror near the bowl for more than a minute or so. If the fish is over-stimulated, habituation to the stimulus will occur and the animal may not respond during the later parts of the experiment.
  3. Record the movements associated with the agonistic display. An aggressive animal will use most of their fins and gill structures in the display. Pay attention to the orientation of the animal to its mirror image and record any changes in the coloration of your fish (look for either "bleaching" or brightening in color). Remove the mirror, allow minute or more for the fish to calm down, and then re-apply the stimulus. To the best of your ability, record the sequence of movements associated with full display. Do the gill opercula open first; or are these structures one of the last to be displayed during an agonistic encounter? Compare your results with that of your classmates. If your animal fails to display or the response is less intense than that of other fish, notify your laboratory instructor (you may need a more aggressive animal before continuing).
  4. Response of Male Fighting Fish to Models. For the remainder of the experiment, paper fish models are used to determine stimulus features are important as releasers of agonistic display. Choose a sheet of construction paper of similar color to your fish. Construct the models (body alone, body with all fins, etc.), as indicated in the Excel s[readsheet. Tape applicator stick handles to the models.
  5. Present the models to your fish in the same order as in results table (start with the body alone, follow with a complete model and continue until you present the body with dorsal, ventral and caudal fins). Move the models slowly up to the fish and then wave them slightly to attract the male's attention. Try to present the models in the same way (same speed of presentation, and similar movements).
  6. Allow the fish a minimum of one minute between the presentation of different models. If you do not get a response after 30 seconds or so, slowly remove the model, let fish rest for another minute and then try the same model again. If the fish responds the second time, use the second results in your report. Record your results by indicating if the male's response is similar to that seen during mirror image stimulation. Use a minus sign if no response is observed, a single plus sign if a response is seen, but at less intensity than a full display, and a double plus sign for a full display. 11
  7. Encounters Between Your Male and Another Fish. When you are finished with the models, move your fish near another group's male and observe the response to a living animal. Do not transfer the fish to the same bowl! Determine which animal is the most aggressive. Compare the data your neighbors collected for the models with your own data and determine if the winner in the encounter was generally more responsive. If available and time permits, a female (or another species of fish) can be used as a stimulus for one of the more aggressive males. Briefly describe the behavior of the male to the female.

More on the behavior, ecology, and feeding of fighting fish is here.



Model Betta splendens to be used for puppets. Cut me out! Try the model first. If your fish doesn't respond, use the realistic model instead and indicate in your data that you are using the realistic fish instead of the model. If you have to use the realistic fish, that means that your fish has lower aggression than usual. More fish to cut out are are here and here (mirror image)