Morphology of taste buds on the gill arches of the mullet Mugil cephalus, and the killifish Fundulus heteroclitus.

The morphology of taste buds on the gill arches of two euryhaline teleosts, the mullet Mugil cephalus, and the killifish Fundulus heteroclitus, were investigated using light microscopic and scanning and transmission electron microscopic techniques. On the mullet gill arches, taste buds were limited to the pharyngeal surfaces of the smooth-surfaced gill rakers. On the killifish gill arches, taste buds were located on the pharyngeal surfaces of all gill rakers and on the gill arch itself at the bases of the gill rakers. Despite dramatic differences in gill-raker structure between these two species, the taste buds themselves were similar ultrastructurally and closely resembled those described in other fishes. Cells within the taste buds included spindle-shaped dark and light cells and basal cells. Ultrastructural features of both the light and dark cells could support either receptor or transport functions. Tufts of microvilli, including one thick microvillus per light cell and numerous thin microvilli per dark cell, protruded at the apex of each taste bud between the ridged surface epithelial cells. Light cells contained numerous tubular membrane elements some of which appeared to open onto the apical surface of the taste bud. Dark cells contained numerous microtubules and apical, electron-lucent vesicles possibly involved in transport.