Knowing more about fruit flies

1. Pictures

Some of the different stages of the fruit fly we looked out for on Day 5 of the module. We learned how to differentiate between the different stages of the larvae, and how to tell between newly formed pupae and "older" pupae, and how to tell if pupal cases were empty or not.




A Drosophila egg under the microscope. Taken from http://www.biologydaily.com/




A 1st-instar Drosophila larva under the microscope. Taken from http://www.ratical.org/co-globalize/MaeWanHo/fruitfly.jpg




first instar (extreme left), 2nd instar (extreme right) and 3rd instar larva (middle) of the fruit fly. Note the differences in length and width. First instar larvae are usually 1-2 mm long, 2nd instar larvae are usually 2-3 mm long, and 3rd instar larvae are around 4 mm long. Also, more developed larvae are usually found higher up in the flask as they are preparing to pupate. The recently hatched larvae would be found nearer the bottom, in the food. Taken from http://www.biology.clc.uc.edu/




Third instar larva (left) and pupa of the fruit fly. Taken from http://www.quest.nasa.gov/




Needless to say, pupa of the fruit fly. The one on the left is a less developed pupa, the prepupa, while the one on the right is in its later stages of metamorphosis. Taken from http://www.openscience.it/

Info about pupa: Sometimes it can be hard to differentiate between pupa and empty pupal cases. Well, there is a simple method to distinguish between the two. Just hold the pupa up to the light. If it allows light to pass through, then it is just an empty pupal case.




And not forgetting the main star itself: the ADULT DROSOPHILA MELANOGASTER, a.k.a FRUIT FLY!!! Taken from http://www.notexactlyrocketscience.wordpress.com/



2. How long?

Well, now that we have since the different stages of growth of the fruit fly, there is still a nagging question: how long does it take for each of the stages of growth? The answer is revealed below:

egg to larva--- 1 day
first instar larva to second instar larva---2 days
second instar larva to third instar larva---2 to 3 days
third instar larva to pupa--- 2 days
pupa to adult--- 6 days

So, adding up the above numbers, it takes a total of 14 days (estimate) for the egg to become an adult drosophila. Compare that to 20 years that a human takes.



3. Experiments
It is now time to explore!!! Explore what? The growth of the fruit fly!!! This is for interested people who would like to know more about the Drosophila Melanogaster (a.k.a fruit fly), and how different conditions can affect their growth through the different stages, particularly through the larval and adult stages.

Firstly, there will be four different set-ups, each with 5 containers of fruit fly larvae with varying compositions of food inside the containers. To prevent inaccuracies, all the larvae used should be newly hatched. There should be around 10-15 larvae in each container (number of larvae used should be the same) The experiment will be carried out for 20 days, which is enough time for the larvae to grow to maturity as adult fruit flies. At the end of the experiment, all the flies in each container will be measured and the average length of the flies will be taken. (Note: A product, FlyNap, can be used to anesthetize the flies to knock them out before measurement)

The results will show which conditions are best for the optimum growth of fruit flies. The below summarization will show the conditions of the various set ups, followed by the 4 different compositions of food in 4 different containers of fruit fly larvae. (Discounting agar powder, water and vinegar). So together, there will be 16 different conditions for the fruit flies (4x4) which can be the best condition for the growth of fruit flies. The best condition will, of course, yield flies which are longer and bigger.


SET-UP 1: Dry conditions, 20 degrees celsius
1. Milo powder, banana, yeast in equal amounts
2. More milo powder, less mashed banana, less yeast
3. More mashed banana, less milo, less yeast
4. more yeast, less banana, less milo

SET-UP 2: Dry conditions, 28 degrees celsius
*same four compositions*

SET-UP 3: Moist conditions, 20 degrees celsius
*same four compositions*

SET-UP 4: Moist conditions, 28 degrees celsius
*same four compositions*


Note: Conditions should be maintained for the whole of the experiment, and there should be no disruptions or external stimulus. The use of thermostats can be used to adjust the different temperatures for the different set-ups. Temperatures should be adjusted beforehand.

Second note: The amount of agar powder and vinegar added should be THE SAME. The amount of water will vary due to the need for moist and dry conditions. However, for each condition (dry or moist), the amount of water should be THE SAME.


HAVE FUN!!!