Ultrastructural development of the vestibular system under conditions of simulated weightlessness.

Electronmicroscopy was used to track the development of the gravity system of frog embryos and larvae which have bred for 5, 7, and 10 d after egg fertilization under conditions of simulated weightlessness on the fast-running horizontal clinostat. Although no differences in the morphologic structure of the organ between test and control animals could be found up to 7 d of development, there is a significant accumulation of vacuoles in sensory epithelia of frog larvae develpoping for 10 d (stage 17) in simulated zero G.