Seesaw size sorter for Drosophila

Davi Bock

Last night I couldn't sleep, my mind was wandering...I thought of how it would be cool to mount a camera on some servos, and have it notice when people were looking at it, and look back at them -- center them in its field of view -- and maybe pay more attention when people at the center of its view were talking. Then I thought about visual systems, how they're hard to figure out, and that made me think of how it's too bad fruit flies (Drosophila melanogaster) are so small, because although there is an arsenal of genetic tools available for the species, their size makes it hard to do electrophysiology on them (to understand their visual systems). And this made me think that a breeding program to increase Drosophila size would be interesting. And this made made me think of a device to automatically sort Drosophila by size. So I turned on the light and started drawing it.

Pretty simple - basically a finely machined metal straw roughly the size of a single fly, mounted on a low-friction pivot point slighly off center -- so it makes a ramp the fly can walk up, and flies of a certain threshold weight, when the reach the end, cause the ramp to descend. And the movement of the straw interrupts an IR beam, which causes a vacuum to be applied, sucking the fly into the "big fly" container. There are a few more details to it -- I made drawings which I'll scan in and post later. The fly walks down the straw because it smells good stuff at the other end. And you could position the sorter at the top of the colony's breeding box or whatever, to make sure that you keep getting 'good' flies as the breeding program continued -- ones that can still fly, and are smart enough to respond to attractive odors.

Seems like this would be a cool project to have running in the background while I pursued a shorter term thesis project. Gotta find a P.I. who gives his students enough rope to try weird stuff like this. Dave Anderson at Caltech was into making weird apparatus to automate fly stuff -- I wonder if anyone at Harvard's like that.

Of course, maybe you can buy automated fly weigher/sorters from Fisher already, who knows? (Well, apparently not.) In any event, it's fun to think about when you can't sleep.

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