[Structure of the vestibular apparatus and ionic composition of the body of Xenopus laevis larvae as affected by weightlessness].

Clawed frog larvae (stages 45-46) that developed for 9 and 8 days beginning with the blastula and tail bud stages, respectively, in the weightless state were investigated. Scanning microscopy of the larval labyrinths did not reveal significant qualitative changes in the receptor and supporting cells of the maculae and in the otolith membrane. Determination of the electrolyte composition (Na, K, Ca, Mg) of the larval body showed no significant changes in the relative content of these elements. The morphometric examinations indicated an increase of the size of the utricular otoliths by 1.3 times as a result of exposure to weightlessness. There was a tendency for a greater asymmetry between the left and right otoliths in the same larva.