How do you construct a choice chamber for Drosophila behavior experiments?

A choice chamber is made by cutting the bottoms off two bottles at marked lines 1 cm and 1.5 cm from the base, then fitting one bottom into the other and taping them together. Poke a center hole with a tape tab for easy access. Label one side A and the other side B. This two-chambered design allows researchers to observe animal behavior studying taxis behavior drosophila in controlled conditions.

What is geotaxis and how is it measured in fruit flies?

Geotaxis is the directional movement of organisms in response to gravity. In the assay, flies are placed in a vertical choice chamber and counted as moving up or down at specific time intervals. The chamber is rotated between measurements to control for chamber orientation. Data reveals whether flies prefer moving against gravity (negative geotaxis) or with gravity (positive geotaxis).

How does the phototaxis experiment determine if flies are attracted to light?

One side of the choice chamber is covered with tin foil to create darkness while the other remains open to light. After 10 minutes, researchers count flies on each side. More flies in the light side indicates positive phototaxis (attraction), while more in the dark side indicates negative phototaxis (repulsion). Equal distribution suggests no light preference.

What role does odor play in the chemotaxis experiment with Drosophila?

Chemotaxis tests fly responses to chemical stimuli using apple cider vinegar and distilled water on cotton balls placed in opposite chamber sides. After 10 minutes, fly distribution indicates attraction or repulsion to the vinegar odor. This measures whether flies preferentially move toward or away from specific chemical cues in their environment.

Why is a null hypothesis important in taxis behavior experiments?

The null hypothesis predicts that flies will show no preference and move randomly, establishing a baseline expectation. Comparing actual results against this random distribution allows researchers to determine whether observed fly behavior is statistically significant or due to chance. This framework distinguishes true behavioral responses from random movement patterns.

How should you prepare a Drosophila colony before beginning taxis assays?

Upon receiving the fly colony, perform a count to verify exactly 40 living individuals are present in the vial. This standardized population size ensures consistent experimental conditions across all trials. Using the same number of flies allows for reliable comparisons between geotaxis, phototaxis, and chemotaxis results.

What data visualization method is recommended for analyzing taxis experiment results?

Plot collected data as bar graphs showing different conditions and time points for each taxis type. This visual representation allows researchers to compare fly responses across geotaxis, phototaxis, and chemotaxis experiments. Bar graphs make it easier to identify patterns and draw inferences about Drosophila melanogaster behavior across different environmental stimuli.

Animal Behavior

Concepts Instructor Prep Student Protocol

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Have you ever left a fruit bowl out for a while and return to discover a fruit fly settlement? But why is the fruit fly attracted to ripe fruit in the first place? In other words, what is the stimulus that tells them where to go? This analysis is part of a wider field called ethology, which is the study of animal behavior.

A stimulus may cause two types of animal movement. Kinesis, which is non-directional or random, or taxis, which is directional. An example of kinesis would be the movement of the flies in random directions when chased away. Conversely, an example of taxis would be the directed movement of the flies back towards the ripe fruit. This specific type of taxis is referred to as chemotaxis and since it is towards the stimulant, food, it is further defined as positive chemotaxis. An example of negative chemotaxis would be the fly moving away from an insect repellent. Another common type of taxis is phototaxis, which is movement is response to a light stimulus. Moths are showing positive phototaxis when they move towards a light source. On the contrary, cockroaches that scuttle away when the light is turned on are being negatively phototactic. Geotaxis, also known as gravitaxis, is movement in response to gravity. Moving in the direction of gravity is positive geotaxis, while movement in the opposite direction is negative geotaxis. There are many other types of taxis, including aerotaxis, barotaxis, hydrotaxis, and magnetotaxis - which are movement in response to oxygen, pressure, water and magnetic fields respectively.

So why do scientists study animal behaviors like these? One of the goals may be to find the genetic basis for the behaviors exhibited by individuals or groups within a species. Sometimes, a behavior can even be traced to a specific mutation in a single gene. On a broader scale, understanding how genetics and behavioral traits are linked can also help us to gain a better understanding of behaviors across the animal kingdom, including our own.

In this lab, you will assess the geotactic, phototactic and chemotactic responses of the fruit fly Drosophila melanogaster, using choice chambers.

Print Procedure Steps

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Making Choice Chambers
- Before beginning the experiments, use one of the Sharpies from the lab table to trace a line around the circumference of the bottom of both bottles. One line should be 1 cm from the base of the bottle and the other should be 1.5 cm from the base of the bottle.
- Use a razor blade to make a small cut in each bottle at the mark.
- Then, insert the scissors and carefully cut along the line until the bottoms of the bottles are removed completely.
- Fit one bottle bottom into the other.
- Tape the bottles together to make a secure chamber.
- Use the razor blade and scissors to poke a hole into the center of the chamber.
- Take a piece of tape and fold the edge onto itself to make a tab and place the tape over the hole. Note: The tab helps with easy removal and reattachment of the tape to the chamber.
- Use the Sharpie to label one side of the chamber A and the other side B.
- Upon receiving the colony of Drosophila, perform a count to make sure there are 40 living individuals in the vial.
Geotaxis
- To perform a geotaxis assay, first attach a clean, empty bottle cap to each end of the choice chamber and turn the fly vial upside down onto its lid.
- Open the tape flap in the center of the choice chamber.
- Insert the funnel into the hole and tap all of the flies into the chamber. HYPOTHESES: The alternate hypothesis is that more flies will be moving against gravity, or up, regardless of the orientation of the choice chamber. Alternatively, if the flies are positively geotactic, then more flies will move down, or with gravity. The null hypothesis is that the flies will have no preference with regard to gravity and will move randomly within the chamber.
- Once the Drosophila are in the chamber, close the tape flap, rotate the chamber so that it stands vertically with side A on the bottom, and start the timer.
- Immediately, count the number of Drosophila that are moving up and the number that are moving down. Record these data for time point 0 in the table.
- After 30 seconds, rotate the chamber so that side B is on the bottom and count the number of Drosophila that are moving up or down. Record these data for time point 30 in the table.
- After 60 seconds, rotate the chamber so that side A is on the bottom again and record the number of moving flies for time point 60. Click Here to download Table 1
- Hold the chamber over the fly vial and carefully open the cap to return all of the Drosophila back to their empty vial.
Phototaxis
- To perform a phototaxis analysis, first cover side A of the choice chamber with tin foil, taking care that the foil reaches to the exact center between the two sides.
- Ensure the caps are secured on both ends of the chamber. HYPOTHESES: In this exercise, the alternative hypothesis is that more flies will be found in the light side of the choice chamber, if the flues are attracted to light, or on the dark side if they are repelled by light. The null hypothesis is that Drosophila will have no preference with regard to either stimulus. Therefore, equal numbers of flies will be found on either side of the choice chamber.
- Open the tape flap in the center of the choice chamber, insert the funnel into the hole, and tap all 40 flies into the chamber as previously described.
- Set the timer to sound an alarm at 10 minutes.
- When the alarm sounds, stop the timer, and count the number of flies in the open side B of the chamber.
- Subtract that number from the total number of flies added to the choice chamber to calculate the number of flies in the covered side A.
- Record these data in the table for time point 10. Click Here to download Table 2
- Carefully, return all of the flies back to their empty vial.
Chemotaxis
- HYPOTHESES: In this exercise, the alternative hypothesis is that more flies will be found on the side of the chamber with the apple cider vinegar if the flies are attracted to the odor. Or, if the flies are repelled by the vinegar, then more of them will be found on the side of the chamber presenting the odorless water. The null hypothesis is that Drosophila will have no preference with regard to either stimulus and will move randomly in the chamber. Use an individual disposable plastic pipette to dispense two drops of the apple cider vinegar onto one cotton ball for side A of the chamber.
- Use an individual disposable plastic pipette to dispense two drops of the distilled water onto a cotton ball for side B of the chamber.
- Fold two pieces of tape over themselves to create individual pieces of double-sided tape and use the tape to attach each cotton ball to the inside of the single bottle cap.
- Screw the bottle caps with the cotton balls onto their corresponding sides of the chamber.
- Transfer all of the flies into the chamber and set the timer to sound an alarm after 10 minutes.
- When the alarm sounds, stop the timer and record the number of flies in each side of the chamber. Click Here to download Table 3
- At the end of the final experiment, funnel the flies into a morgue tube containing 70% ethanol.
- Dismantle the choice chambers for recycling. NOTE: Since all of the chemicals used in these experiments are lab safe, the liquids can be disposed of down the sink, the chambers rinsed, and the solids can be thrown away in the trash.
Results
- Gather all of the data collected for the geotaxis, phototaxis, and chemotaxis experiments.
- Plot these values as bar graphs for different conditions and different time points.
- Use these data to draw inferences about the behavior of drosophila melanogaster.