[Surface structure of the otolithic organs of the tadpole of the clawed toad Xenopus laevis].

Beginning from the blastula and tail bud stages, 15 larvae of the clawed toad were kept in three EMKON containers at temperature 15 degrees for 8-9 days. Structure of the hair cells and otolith membrane of the larval otolithic organs was examined with a light microscope, TEM and SEM. In contrast to previous studies, it was found that at the stages mentioned larval otolithic organs are presented not by two, but by three maculae, i.e. the utricular, saccular and lagenar ones with two otoliths. Saccular and lagenar maculae are covered by a common otolith membrane. Separate otoconia may loose from the otolith membrane, this process being enhanced by fixation. Within the maculae, receptor cells differ with respect to the structure of hair bundles. Basing on the morphology of ciliary tufts, 4 types of the hair cells were identified. However, TEM examination did not reveal significant differences in the ultrastructure of these types of cells. Maculae of the three otolithic organs varied in the cell type patterns and cell polarization. No continuous row of the immature hair cells was found along the perimeter of the maculae.