worms under pressure
Avery L. (1987) Worm Breeder’s Gazette 10:139.
The reason worms don’t fall off an upside-down plate is surface tension. The force pressing the worm to the agar surface is roughly the surface tension of water times the perimeter of a sagittal section: 10+E5 -10+E6 times the weight of the worm for a young L1. Because of this, I thought worms might be able to survive high-speed centrifugation. Since Gary Ruvkun bet me ten dollars they wouldn’t, I did the experiment.
The worms were very young L1s prepared by hatching eggs in the absence of food. I first spun some at 100,000G (32,500 rpm in an 80Ti rotor). The spin was as short as I could make it: 5 min acceleration, a few seconds at speed, and 5 min deceleration. The worms were unaffected. About half of them thrashed in liquid, all looked normal in Nomarski, and all grew up to healthy, active adults and produced large broods in the normal time.
Next I spun some more worms at 460,000G (70,000 rpm, as fast as our centrifuge would go). These worms were all clearly abnormal in Nomarski. There were usually empty spaces between the buccal cavity and the head cuticle, and the tail often had similar holes. In some the viscera pulled away from the cuticle in other places, too. Many individual cells were killed. Most of these worms arrested as L1s, though some continued to move. But some of them grew up to become healthy adults and produce progeny.
Spinning at high speed stresses worms in three ways: there are forces flattening them against the bottom of the tube (like the surface tension forces on a plate), a very high static pressure that will affect chemical reactions (e.g. dissolution of gases, as in the bends), and forces causing components of the worm to sediment with respect to each other. Judging from the Nomarski result, it might be the last of these that bothers the worms most, though they are very resistant to all three.