Tips on maintaining fruitflies by yourself!
By Raymond on Feb 28, 2009 in Lab
Undergraduate Lab
Tips on maintaining fruitflies by yourself!
Recipe for flies: Yummy!!!
| Water | 50L |
| Agar | 470g |
| Sucrose | 1580g |
| Glucose | 3160g |
| Preservative | 142g |
| Doxycycline (antibiotics) | 2.1g |
| Amoxicillin (antibiotics) | 4.16g |
| sodium tartrate (it is an emulsifier used in food like jellies) | 438g |
| calcium chloride | 36.3g |
| maize powder | 3885g |
Of course, you may change the amount according to the proportion. You can use a great pot to “cook” the food, or just a beaker with a microwave oven.
This is the formula in our lab. You can find more useful recipes and cooking instructions in the following website of Bloomington:
http://flystocks.bio.indiana.edu/Fly_Work/media-recipes/media-recipes.htm
Dry Yeast can also be spread on the surface of the medium to prevent the growth of fungi and improve the growth of larvae
4 “types” of medium:
Small/Big vials: choose the appropriate one according to the amount of flies you need. For instance, if you just want to obtain 10~50flies in the next generation, use small vials. If you want hundreds, get big vials. If the genotypic frequency of the required genotype in the next generation is small, it is still better to use large vials, or you might get angry when you can find only one fly you want in the small vials.
Some examples:
- Small vial, thin medium: lifespan, climbing assay, temporary storage of flies (e.g. virgins) for 1-3days
- Small vial, thick medium: storage, backcross, cross (if you need small number of flies)
- Big vial, thin medium: temporary storage of flies for 1-4days, e.g. when we have to prepare hundreds of flies for an olfactory learning experiment. It is adviced to put a piece of small round-shaped paper over the medium to restrict the diet of flies, and a fan-shaped filter paper inside the vial so that flies would have a dry place to stand on. You’ll be helpless when you find that your dear flies stuck on the sticky food…
- Big vial, thick medium: storage and cross
Some tools for keeping flies include:
-
- Microscope or stereoscope for observation of fly, together with carbon dioxide for anesthesia and brush pens for picking flies
- Vials for keeping flies
- An automatic autoclave for sterilization of paper and small tools
- Fly storage rooms with suitable temperature and humidity (meaning air-conditioner and humidifier)
Environmental conditions:
Temperature:
18℃ :for storage or backup of flies which won’t be used in short term. Generally, it takes around 3 weeks for the flies to complete one generation in this temperature. Flies cannot survive if it drops below 18, as you know, insects are cold-blooded.
If you are using GAL4-GAL80 gene switch, in which the permissive temperature is 30℃, you may want to keep the flies in 18 to prevent leckage expression until you want to switch the gene on.
25℃ : I keep my flies I use recently in this temperature.
28 ℃: When I do lifespan assay, I sometimes put the flies in 28℃ to facilitate their metabolism, so that they can live shorter or die earlier and I do not have to count them for 2-3months.
30℃ : You will need it if you are using the GAL4-GAL80 gene switch (permissive temperature).
Over 30℃: Are you doing a heat shock experiment?
Humidity:
You may find that the growing rate and conditions are not exactly the same if the room is too wet or too dry. Generally flies love relatively high humidity. If you just want to maintain some flies at home, you may put the vials in a few centimeters of water.
Light:
To keep the room similar to natural environment, you may install a system which automatically turns off the light at night and on in the morning.
Maintain flies in 25℃:
Day 1
It is to your benefit to “synchronize” the generation cycles of your flies. Otherwise, you will find that your brain capacity is too small to remember when you should transfer the flies or insert papers or pick virgins with so many vials of flies!
Better to put some dry yeast on the surface.
Sufficient number of flies in a vial can also prevent mould.
You may want to put some paper into the vial so that the flies will have a dry and safe place to stay and will not need to swim over the “ocean of food” when the medium is full of larvae. No need care about the shape of the paper, but it is better that the paper is deeply inserted into the medium, otherwise when you transfer the flies after eclosion, you will feel very troublesome if the sticky paper full of larvae drop down to your hand. The paper should not cover too much of the medium, or else the females will have no place to lay their eggs.
Also, the paper should be sterilized in high temperature to prevent the growth of mould, parasites or even eggs of flies of another genotype. You may use newspaper if you just want to have some flies at home.
An “ocean of larvae” A vial with paper inserted
On around day 9 and 10, you will see the maggot stuck tightly on the paper and the wall of the vial. It takes a maggot around 3 days to become adult fly.
Day 11 or 12
Adult flies appear on Day 11 and you can start to collect virgins on Day 12.
Tips on selecting virgins:
First, be clear with the purpose of picking virgins, and how strict is the virginity required for the experiment. If you will use the virgin in crosses to produce double transgenic flies which can be maintained through generation, and if the genotypes of flies cannot be well determined by phenotype, you have to use “strict virgins” with all the clear markers a virgin should have: pale color body and black dot in abdomen. To obtain strict virgins, you have to screen the vials every 2 hours.
If you just use the virgins for one time purpose, you may screen and clear the vials every 4-8hours and assume that all the females are virgins.
So, determine the purpose of your experiment and use your logic to analyze which is more important, virginity or time.
On Day 11, on which a small part of flies have just undergone eclosion, you may clear the flies in the vials and put it in 18℃ overnight. Come back to the lab early morning and hopefully you will find many lovely white virgins when you place the vials back to room temperature.
Also, it may not be to your advantage if you transfer your flies to new vials on Tuesday… you’ll find that you have to come back to the lab on Saturday and Sunday after 11 days. (well, don’t tell your boss…)
You may also increase the number of vials so that you can pick up more virgins at one time (but then you will have more vials to wash)
Tips on keeping the genotype of your flies pure:
You know, it can be disastrous to your experiments and thesis if the genotype of your flies is not correct. Be very careful about this.
- Label the vials clearly. You may mix the stock if you are having two strains named “11a11” and “11a17”.
- Better not to use the same vial of flies for maintenance and experiment. For instance, if you want to pick virgins, you should keep at least two vials of flies, one for giving birth to next generation, and one for experiments. Wandering flies get into your vial when you plug in and out the bungs.
- Better not to “borrow” the flies from your colleagues, unless you will just use it one time and you are not going to cross them with your own flies for new genotypes, or you think that your colleagues are more careful than you are.
- Keep flies you are not using at 18℃ might help to decrease the rate of unexpected mutation in your mutant genes This is especially true for double balancers.
- Check if the correct phenotypes still present periodically.
- Better not to transfer your flies if you find that many flies are flying in the lab.
Useful links:
http://www.protocol-online.org/prot/Model_Organisms/Drosophila/Drosophila_Culture___Handling/
Protocol Online: experiment protocols for Drosophila
http://flybase.org/
Flybase: stocks
http://flystocks.bio.indiana.edu/
Bloomington Drosophila Stock Center at Indiana University
http://flybrain.neurobio.arizona.edu/
Flybrain: Database of Drosophila nervous system
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