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Several of the heat shocked embryos displayed motoneuron disturbances when viewed under the microscope. Whereas normal somites are the same size, those whose development was disturbed had somites of varying size.

We treated 90 embryos to heat shock and 10 embryos were kept as controls. Of the 90 treated embryos, 77 survived the 24-hour incubation period and were fixed and stained. Five of the 10 controls survived and displayed normal somite development (Figure 1).

Of the 77 surviving experimental embryos, 8 hatched and were swimming around. All 8 of the fish that hatched showed visible disturbances in their motoneural axons (Figure 2).

When treated, embryos had developed approximately 15-20 somites. The abnormalality did not appear immediately after treatment, but there was a zone of regular axons before the abnormal axon. Since we did not record the treatment stage and final stage of each embryo, it was imposible to determine exactly how large the zone was.

©Cebra-Thomas, 2000

Last Modified: 10 May 2004

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