Objectives:

• become familiar with studying the behavior of fish
• gain experience in quantitative behavioral techniques
• explore behavior patterns of communication

Discussion and Pre-Lab Preparation: The guppy, Poecilia reticulata, is a fresh-water teleost fish in the family Poeciliidae. It is native to mountain streams of Trinidad and northeastern South America but has been introduced to many parts of the world in mosquito control programs. They are also a favorite of the aquarium trade with individuals from many individual strains judged in championships. There are instructions on how to maintain and breed them. Here are more care instructions. You can browse to your hearts content in the following list of guppy links. Guppies are live-bearing, with brood sizes of 1-25, according to the size of the female. Maturation occurs after 6-8 weeks at which point the male anal fin develops into an elongated organ, the gonopodium, which is used for internal fertilization. Several successive broods may arise from a single insemination. With pronounced sexual dimorphism, female guppies are large with silvery-tan coloration, while males are small and brightly colored. Variation in coloration are common among natural strains and relate to predation pressure from piscivorous fish. Differences in pigment variants have been enhanced through extensive breeding leading to some individuals with spectacular coloration.

When removing fish from the tank always use a net. If you must handle a fish, wet your hands throughly before doing so. Touching fish with a dry object will scrape away mucus and expose the skin to infection. Young produced during the project may be removed from the tank and kept in a jar, or returned to the stock tank. Alternatively, you may wish to study the young in the tank and include a section on this in your report.

Figure 1. Basic Fish Morphology. The male guppy, Poecilia reticulata (Poecilidae), uses his intromittent organ, a modified anal fin, to inseminate the female. Here it is being swung forward prior to copulation.

List of common behavior patterns in guppy

Any meaningful study of animal behavior depends on the availability of a comprehensive ethogram. You cannot ask proper questions about behavior until you are thoroughly familiar with the behavior patterns of the species you are studying. In behavior, as in any sceince, we begin with observations. This is perhaps the most difficult phase of the study, for it takes considerable practice and concentration in order to be able to see what an animal is doing. Anyone can watch an animal, but it is an acquired skill to be able to distinguish its behavior patterns. Once trained, however, an observer can apply this skill to the study of any species, with little modification.  A list of behavior patterns in guppies is available. Terminology and illustrations are modified from Baerands et al. 1955. Ethological studies on Lebistes reticulatus (Peters). I: An analysis of the male courtship pattern. Behaviour 8: 249-334.1955. Feel free to add other behaviors to this list or modify definitions of existing ones as you see them. Describe any changes clearly.

• AP = Approach one fish of either sex swims to another
• AT = Attack one fish of either sex bites or rushes at another
• BC = Biting Cloaca during Following Behind (see below) male bites female near the cloaca (genital pore)
• CH = Chafing rubbing any part of the body against any object; may help remove external parasites
• CM = Chasing by Male usually directed toward female as male attempts Gonopodial Contact (see below)
• CF = Chasing by Female may be directed at male or another female
• DJ = Display Jump male in Signoid darts away suddenly
• FB = Following Behind male swims behind female
• FS = Following Side male swims beside female
• GC = Gonopodial Contact male touches female's cloaca briefly with his gonopodium (intromittent organ)
• GS = Gonopodial Swing male brings gonopodium forward from resting position without directing it towards female's cloaca
• GT = Gonopodial Thrust male swing gonopodium toward female's cloaca, without making contact
• L = Luring alternating Approach and Retreat by a male over a short distance toward and away from female. May look as though male attached to female by rubber band.
• P = Posturing male orients towards female's head, but not with body in Signoid curve (see below)
• R = Retreat male leaves female (can be modified for interactions between males, etc)
• SH = Sigmoid High intensity usually directed towards females. Male flexes his body into a strong "C" or "S" shape and vibrates rapidly. Male may be at various angles to female, or even facing away. Degree of intensity (ie. high, medium or low) can depend on either duration of amount of flex in the male's body. Criterion for intensity should be given.
• SL = Sigmoid Low intensity as above, but with either shorter duration or less flex in the male's body
• ST = Stopped fish becomes motionless, on the bottom or above it
• SW = Swimming moving rapidly or slowly

Figure 3. Advanced courting activities.
 
 

Figure 4. Copulation attempt

Exercise 1:

Question: Which behavior patterns are present during courtship in Poecilia reticulata?

Preparation: Social encounters of guppies are staged in observation tanks for groups of three students each. The tank contains gravel and is filled with de-chlorinated water at a depth of 20cm. We need a watch to record the timing of events, a small aquarium net, some fish food (flakes) and a divider.

Procedures: Place 3 females of different size and coloration into the tank. Add 2 males from a separate holding tank where they had been kept isolated for one day. Set up an observation schedule of periods not less than 15 minutes in duration and observe the animals without disturbing them. Remove the divider and begin by watching everything the fish do, including their responses to food and to other fish. Soon you will begin to recognize patterns of movement, like folding the dorsal fin or bending the caudal peduncle, or nipping the water surface in feeding, because you will see the same actions repeatedly. Once you have discovered the behavior patterns of your animals you will have units of behavior with which to work further.

At this point in the study you should begin to record in a notebook everything you notice during your observation periods. Try to describe behavior patterns accurately, and give a descriptive name to each kind. An example is: Gonopodial Thrust - the male swings his gonopodium towards the female's cloaca. This may or may not be followed by a Gonopodial Contact, depending on evasive behavior by the female.

From your records (= protocols) you can extract an inventory of behavior patterns with a description of each one. Such ethograms are important as studies of the "morphology" of species-typical behavior, as material for comparative study of closely or distantly related species (or higher taxa), and as a beginning point for asking further questions about behavior. See Figures 2, 3 and 4 for examples of mating behavior. You can expect differences in the behavior of your fish, for these authors did not work with the same strain of guppy, and because the behavior of these fish is still incompletely known. Consult the list preceding the figures for important behavior patterns.

Each time you move the fish will react to you, but they will soon habituate to your presence if you avoid sudden movements. Keep your notebook well away from the tank when recording data, and preferably held so that your hand movements during writing are not seen by the fish. If the fish are seriously disturbed by your presence, turn off the room lights so that the tank alone is illuminated, and wear dark clothing.

Answer questions: How do such observations relate to the scientific method? Basic behavioral observations are associated with which point of the cycle of scientific inference - preliminary observations, formulate question and hypotheses, design, conduct, and analyze experiments, or communicate results?

Exercise 2:

Question: How can we obtain quantitative behavioral data from guppies?

Preparation: You will have noticed by this stage that some behavior patterns vary in degree of completeness or exaggeration, so that it is difficult at times to be sure that a fish made a given movement, while other patterns seem to be complete and the same each time that they are given. Try to determine which patterns vary in this manner, and which do not. You may, for example, notice Gonopodial Swinging where the gonopodium is only swung part-way forward. Variation in amplitude is one kind of intensity difference; we could say that Gonopodial Swinging occurs at two different intensities (= here degrees of completeness). Are there in fact two distinct intensities of this behavior, or is it a continuum?

The duration of a behavior pattern can serve as a measure of intensity as well. Use the stopwatch provided to time the duration of a few different patterns and determine how much variance there is. You will need an adequate sample for each pattern before you can determine the amount of variance. An example from Gonopodial Swinging would be the length of time the gonopodium is held forward. You may consider recording behavior using techniques similar to those introduced in the lab on crayfish fighting.

Another measure of intensity is the frequency with which a behavior pattern occurs, that is the number of occurrences per unit time. A change in protocol will enable you to record these measurement. First adopt a letter code for each pattern that you wish to study. Observe only one fish at a time and record the letter code of each behavior pattern in order of occurrence. Using a clock or timer, draw a line through the protocol at one minute intervals

Preparation: see exercise 1

Procedures: Quantify the behavior of a single male guppy in one of the above ways.

Answer questions: What are the particular advantages of each appraoch? What are the draw backs? What are the trade-offs?

last modified: 9/29/03