Development of taste organs in Rana temporaria. Transmission and scanning electron microscopic study.

In tadpoles of Rana temporaria two successive generations of taste organs: taste buds (TBs) and taste disks were studied. The TBs are located in the apices of oral premetamorphic papillae. Each TB consists of vertically elongated receptor cells (probably taste) and supporting cells. No basal (Merkel) cells were observed there. Morphologically, two types of receptor cells have been distinguished in a TB. Complete synaptic structures were observed in the TBs between the 30th and 41st of Gosner's (1960) developmental stages, though synaptic vesicles occur already at stage 26. The taste disks consist of taste cells, supporting cells and basal cells. Dense-core synaptic vesicles occur in the gustatory cells at stage 41, but complete synaptic structures were not observed earlier than at stage 45. Synaptic junctions observed at some of the gustatory cells seem to be reciprocal (bidirectional).