Exercise 30 - Simple Behaviors

STUDENT OBJECTIVE

Using a chi-square analysis, students interpret the responses of Drosophila to light and gravity. If time permits, students can investigate chemotaxis using a simple tee-choice apparatus.

EQUIPMENT AMOUNT (Class of 24 with 8 groups)
Lamp, swing arm with 100 watt bulb 8/lab


MATERIALS

Fruit flies, live 15 flies/group
Vials, plastic 10 cm x 3 cm diameter and stopper (CBS#17-3085, 3086)* 2/group
Tee tubes, 8 mm, rubber stoppers to fit plastic vials above 1/group
Tape (clear) 1 roll/lab
Marking pencil 1/group
Ruler 1/group
Cardboard tube, 30 cm x 4 cm diameter (from center of paper towel roll) 1/group
Stoppers, rubber #8 or #9 2/group
Ring stand 1/group
Clamps 2/group
Ring, 3" diameter iron 1/group
Thermometer 1/group
Beaker, 400 ml 1/group
Beaker, 800 ml 1/group
Stick, wooden, 1/8" diameter x 6" 1/group
Crisper, plastic (to hold materials) 1/group
Black cloth 24" x 24" 1/group
For instructor use only
     Paper punch
     Fiber strapping tape
     Drosophila cultures, two weeks old
     Anesthetizer, ether, camel hair brush, plastic vials with stoppers

PREPARATION

Two Weeks before Lab

Instructions are given in Exercise #9 for culturing Drosophila successfully. Use wild-type flies. There is no need to separate sexes for this exercise. A stock culture chamber should be started with 20 females and 10 males. Place in a 22-24 ° C area with adequate moisture. After 7-8 days, remove all the adults. Emergence of new adults should occur in 12-13 days.

Week before Lab

  1. The ends of the cardboard tubes should be reinforced with a wrapping of fiber strapping tape. Two holes should be punched across from each other, one-eighth inch in from the edge of one end of the tube. The completed chamber should have a rubber stopper on each end that fits securely and permits no light passage.

  2. Assemble tee-tube apparatus as shown in lab manual (fig. 30.4).

Several Hours before Lab

The Drosophila should be lightly anesthetized and 15 counted into each vial. Before giving to the students, observe to make certain flies are alive.

NOTES

  1. The cardboard tube used as a sleeve for the plastic vials can be cut from a mailing tube, or an empty paper toweling tube can be used.

  2. All vials should be washed and rinsed well to remove the possibility of the flies responding to contaminants in the vial.

  3. A piece of tissue over the open end of the cardboard tube during the experiments is an excellent light diffuser.

CLASSROOM SUGGESTIONS

Drosophila can be difficult to count because they respond to the slightest disturbance. Students can divide the responsibility of counting each section of the tube during the trials. Instructors might want to increase the number of flies observed to obtain a larger set of data. Each group can test two vials and not increase the laboratory time by very much.

ANSWERS TO CRITICAL THINKING QUESTIONS

  1. Attempt to control for heat in several ways. Water container between flies and light source filters out much of the heat. Using a thermometer to check temperatures, will tell whether heat is an influence. There is still a possibility that infra red energy is passing into the vials and triggering the flies' movement.

  2. The T tube chambers contained were saturated by placing wet cotton in them. There should be no difference between the chambers due to humidity.

  3. These two taxes favor emergence. Fruit flies inside a rotten fruit or under a layer of rotting vegetation will move in such a way as to escape entrapment.

SUPPLEMENTAL MATERIALS

Bird Brain--The Mystery of Bird Navigation (NOVA), 27-minute film. Chicago, IL: Time-Life.

The Guanaco of Patagonia: Study of Behavior and Ecology, 29-minute film. Ames, IA: Iowa State University. #57624

Protist Behavior, 11-minute film. Rochester, NY: Ward's. #140W2015

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