Living Organism Care- Drosophila

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Quick Start Information:

  • Remove the Drosophila vial from the shipping container and inspect thoroughly
  • Remove the sticky tape that is holding the foam plug securely during transportation, but leave the foam plugs in place otherwise your flies will escape.
  • Store cultures away from direct sunlight
  • Maintain vials between 20 and 25° C
  • To reduce the potential of mite infestation, stand the culture containers together in 1cm of water

Background 

  • The genus Drosophila has over 1,500 species.
  • Select Drosophila species have sperm cells that are 35 times longer than a human sperm.
  • One of the first model organisms used in biology was Drosophila melanogaster. 
  • The average lifespan of an adult fruit fly is between 35-45 days.
  • Small reptiles and amphibians consume wingless Drosophila as a nutritious food source. 
        • Domain: Eukarya
        • Kingdom: Animalia
        • Phylum: Arthropoda
        • Class: Insecta
        • Order: Diptera
        • Family: Drosophilidae
        • Genus: Drosophila
        • Species: melanogaster, virilis, or hydei

Preparation:  

The cultures will be shipped to you in plastic vials. Contained within the vials is a media as a food source. Within each vial, you will find adult flies, larvae, pupae and eggs.
The Flies will continuously reproduce within the shipping vial for approximately 3 weeks after you receive them.  

Housing

Drosophila can be housed in either glass or plastic vessels. These need to be clean and sterilised with boiling water prior to the introduction of media and flies. Polyurethane foam is an ideal plug, but cotton wool wrapped in cotton cloth is also suitable. Your selection of plug needs to allow air to reach the flies.

Feeding

Drosophlia can be raised on a variety of materials. We offer an easy to use instant medium that requires no cooking. The powder medium is placed into the culture vessel, water is added and then a sprinkle of yeast is placed on top of the final surface. After a short period of time, flies may be added. This medium will look different to the cooked version that we supply the flies on, but both work effectively, and both are used within our own laboratory.

Yeast is typically included in media recipes and care needs to be taken to ensure that yeast is not overused. A metabolic by-product of yeast is CO2. Large amounts of CO2 can cause sterilisation of the males, or may even be fatal to the flies in the colony. Please heed the warning and only use the recommended amount.

 

Maintaining and Culturing

Life cycle:

  • There are four stages in the life cycle of Drosophila; egg, larva, pupa and adult.
  • The day after the egg is laid, the larvae hatch. Approximately 8-14 days later, the larvae enter the pupa (puparium) stage. Metamorphosis occurs over 5-8 days. The colour of the pupae becomes darker just prior to when the adults emerge.
  • At first the newly emerged fly is light in colour, the wings are un-expanded and the abdomen is long. However, in a few hours the wings expand, the abdomen becomes more rotund and the colour gradually darkens. Two days after emerging, the females can start laying eggs and will be fertile for their entire lives. (insert drosophila life cycle image)

Virgin flies:

  • You need virgin females for work with genetics.
  • Female drosophila can store sperm from a single insemination for the major portion of her reproductive life. This means that it is very important to select virgin females when conducting genetic crosses. Older males will mate with newly emerged females. The simplest way of controlling this is to remove all adults from the vessel at the pupae development stage.
  • To ensure virginity, females need to be identified before they are 15 hours old. Removal and sexing of all new hatching is best done twice each day, once at the start, and once at the end. The flies tend to hatch in greater numbers toward the start of the day.

Anaesthetising:

  • Flies need to be immobilised for sexing under a stereo microscope. There are several methods that can be employed to safely do this. We offer two products, one based on the release of CO2  and the other based on a solvent (not ether), FlyNap®
  • Do not anaesthetise flies in the culture vessel. Transfer them to another vessel. To transfer you will need an empty container with a similar, but not necessarily the same size neck opening. For the action of transfer, you need to control where the flies are. You can cause all the flies to go to the bottom of the culture vessel if you firmly tap the base of the vessel on a table. The flies will drop to the bottom. You can then quickly remove the plug, invert the vessel directly above the receiving vessel’s neck and tap the combination unit again on the table. The flies will fall from the media end of the culture vessel (now the top), through the adjoining necks, to the bottom of the empty vessel (near the table). Re-plug each immediately.
  • The flies in the new vessel are ready for anesthetizing. Regardless of the method you use, follow the instruction for anaesthetising carefully as it is possible to over anesthetise to the point of death.
  • The anesthetized flies can now be placed on a white card or sheet of paper for examination with a stereo microscope.
  • When transferring anesthetized flies into a new vessel containing media, place the receiving vessel on its side and place the flies on the internal, dry, side of the vessel. Plug the neck but leave the vessel on its side until the flies are active again. If they are placed directly onto the media, they may adhere to the surface and “drown” or die before recovery.

Sexing:

  • When doing genetic experiments it is very important that the flies be sexed correctly. The easiest and most reliable method is via microscopic examination of the genital organs. With the use of a soft hair brush (G10.60), flies can be quickly moved into the view of the microscope and then grouped as male or female. The male genitalia is surrounded by heavy dark coloured bristles. The females are light. In males the tip of the abdomen is more rounded than in females. In general, male files are overall smaller than females, but size alone is not a reliable method of sexing.

 

Mating for genetics:

  • Prepare your vessels with media. Label and date each vial that will receive the crosses with the characteristics of the parents. The first cross between strains is called the parental generation, the P1. The progeny of this cross is the first filial generation, F1. The next generation is F2.
  • Place about 6 female virgins into a vial containing approximately 6 males from another strain. For reciprocal results set up additional vials but reverse the sex of each strain.
  • When pupae start to appear on the glass wall, remove the adults. This will avoid generational confusion.
  • When progeny hatch, characteristics can be examined with a stereo microscope. 

Summary:

Flies from Southern Biological are mature adults and should not be used in genetic mating.

Virgin females, isolated from the progeny, will be required for genetic work.

  • Your delivery from Southern Biological arrives with mature adults. 
  • 8-14 days later, larvae enter pupae stage
  • Remove adults from vial
  • 5-8 days later flies emerge from pupae
  • Remove new flies twice per day and sex. Isolate males and females.
  • Use virgin females for genetic work.

Disposal: 

Southern Biological provides living organisms for educational and scientific study. We strongly advise against releasing Drosophila or any other organisms into the environment. In most circumstances, it is illegal to release lab reared animals and organisms (regardless of whether they are indigenous) into the natural environment without a permit. Drosophila are considered a pest species. For small vivarium pets, such as frogs or lizards the flies can be a nutritious food source

To euthanize the flies, you can place the vials in a snap lock bag or container and freeze for 48 hours. The deceased organisms should then be disposed of in a municipal solid waste container immediately.                                 

 

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