As a mammalian cell biologist adrift in a Drosophila genetics lab, my contact with flies is fairly minimal. Through the thin wall separating my desk from the fly room, I can hear the loud repetitive thumping that accompanies the transfer of one colony of flies to a new vial, punctuating the laughter and music of their human supervisors. About once a week the oxygen depletion alarm goes off from excessive use of the carbon dioxide employed to anesthetize the insects, and the PhD students have to troop out with long-suffering expressions and wait for the oxygen levels to go back to normal. It’s not just noise, either: you can always tell when a new undergraduate helper is maintaining the stocks because runaway flies will suddenly appear everywhere in the lab and office, crawling over keyboard and bench in a bewildered search for the big yeasty blob in which they happily pupariated – or failing that, a ripe banana.
Fruit flies may have a long and illustrious history as a model organism, but they aren’t exactly the heavy-weights of the animal kingdom in terms of robustness. Unlike worms, cell lines and the embryos of higher organisms, you can’t freeze them down. Hence, any new transgenic flies have to be passed once or twice a week in perpetuity: there are strains in our incubators still knocking around from Thomas Hunt Morgan’s time. So our lab’s fly collection is massive: thousands of vials full of mutated insects with extra limbs, warped wings and all shades of phenotype in between, lined up in tray after tray. Needless to say, the task of keeping them going is incredibly tedious and the half-life of any young helper is only a few months.
Also, flies don’t weather travel very well. It’s a sad truth that more than half of the flies sent to us by American colleagues, or by the all-important Bloomington Drosophila Stock Center, arrive DOA. It’s all down to UK Customs: the last Fedex shipment of flies we received was held for four weeks at Heathrow, which is presumably how long it takes a Home Office bureaucrat to work out that a fruit fly highly crippled for life outside the yeasty vial is actually not harmful. But even a few days in the post can spell the death of these frail little creatures.
Which is why I was surprised this morning to find an intact Drosophila corpse inside an Eppendorf tube, itself inside a beaker full of clean Eppendorf tubes that had been sealed and autoclaved. Now that’s what I call a sturdy exoskeleton.