ABSTRACT
In taste buds of fish, as in other venebrates, the elongated cells apically bear microvilli which together form the taste bud receptor area. As seen in the scanning electron microscope (SEM), the receptor areas of most species of fish contain two kinds of microvilli, large and small. In some fish however, three or four different types of microvillar structures have been observed. Transmission electron microscopic (TEM) studies revealed that all microvilli (receptor villi) belong to two main types of elongated cells, the electron lucent light cells and the electron denser dark cells. Here we demonstrate that in distinct species of fish both types of cells may have several subtypes. One subtype of light cell always ends in one large apical microvillus, the other subtype{s) show different numbers of distinctly shaped microvilli. The most common dark cell subtype normally bears small and undivided microvilli; other dark cell subtypes have microvilli of variable shapes. The number of
212 Fish Chemosenses
elongated taste bud cells and the respective number of different types of microvilli may vary in fish of different systematic position and even between fish belonging to the same genus. We therefore postulate that in fish, taste bud micromorphology is species specific. It is likely that fish taste buds evolved while fish took possession of their own distinct ecological niche. Key Words: Receptor area; Taste bud; Microvilli; Receptor villi; Ultrastructure; Evolution; Electron microscopy.
