Structural Organization of the Taste Apparatus in Characins (Characidae,Teleostei)

The morphology and distribution of taste buds in the outer integument of the body and in the oral cavity of two forms (blind cave and sighted terrestrial ones) of the astyanax Astyanax fasciatus and in intact and blinded individuals of the Buenos Aires tetra Hyphessobrycon anisitsi have been studied using electronic scanning and light microscopy. In sighted individuals of both species, the morphometric parameters of the taste apparatus and the distribution of taste receptors are similar; the taste apparatus in the oral cavity is more developed than in the outer covers. Morphologically different taste zones were found in the oral cavity of characins. In blind fish, the taste apparatus of the maxillary zones is distinguished by smaller taste buds and a greater density of their distribution. The sensory field of taste buds in blind and sighted individuals of astyanax and tetra has a similar ultrastructure; it is formed by taste cells of three types. In blind astyanaxes and blinded individuals of tetra, numerous modified epidermal cells were found for the first time in the epithelium of the taste zones and in contact with taste buds, which are regarded as tactile receptors and a constituent element of polysensory taste-tactile complexes localized in blind fish in mainly ventral sensory zones.