Heterogeneity of fish taste bud ultrastructure as demonstrated in the holosteans Amia calva and Lepisosteus oculatus

Abstract

Taste buds are the peripheral sensory organs of the gustatory system. They occur in all taxa of vertebrates and are pear-shaped intra-epithelial organs of about 80 microm height and 50 microm width. Taste buds mainly consist of specialized epithelial cells, which synapse at their bases and therefore are secondary sensory cells. Taste buds have been described based on studies of teleostean species, but it turned out that the ultrastructure of teleostean taste buds may differ between distinct systematic groups and that this description is not representative of those taste buds in other main taxa of fishes, such as selachians, holosteans and dipnoans. Furthermore, it is not known how variable the micromorphologies of non-teleostean taste buds are. For this reason the taste buds of two holosteans, Lepisosteus oculatus and Amia calva, were investigated and compared. While in both species the taste buds are of the same shapes and sizes, the cellular components of their sensory epithelia differ: in Lepisosteus taste buds comprise two types of elongated light cells and one type of dark cells. In contrast, Amia taste buds contain only one type of light, but two types of dark elongated cells. Afferent synapses are common in the buds of both species, efferent synapses occur only in Lepisosteus taste buds. These differences show that even in the small group of holostean fishes the taste buds are differently organized. Consequently, a representative type of fish taste buds does not exist.

Surface Ultrastructure of the Gills of Odontesthes bonariensis (Valenciennes, 1835)(Teleostei: Atheriniformes) from a Temperate Shallow Lake

“…In most fishes, they are not only distributed in the oropharyngeal cavity of the mouth, but also on the basal parts of the gill arches, and they are frequently found in the skin (Fishelson et al, 2004;Xiong et al). Taste buds are the peripheral sense organs of the gustatory system of fish as well as of other vertebrates; they allow animals to recognize food through detection of distinct chemical substances at short distances (Reutter et al, 2000). The presence of taste buds on both gill arches and rakers of O. bonariensis may be associated with their participation in tasting at the pharyngeal region.…”

Distribution of different taste buds and expression of α-gustducin in the barbells of yellow catfish (Pelteobagrus fulvidraco)

“…The morphology and physiology of the fish gustatory system have been summarized by several authors (Lamb and Caprio 1993;Reutter and Witt 1996;Ogawa and Caprio 2000;Tagliafierro and Zaccone 2001;Northcutt 2005). The cytology of TB in catfishes has been thoroughly studied: poicillids and lungfish (Storch and Welsch 1970;Whitear 1971;Reutter et al 1974;Grover-Johnson and Farbman 1976;Reutter 1978Reutter , 1991; in holostean fishes (Reutter et al 2000); in the tench (Zuwala and Jakubowski 1993); in zebrafish (Hansen et al 2002) and recently in gobies, blennies and cardinal fish species .…”

Ligand-specific induction of endocytosis in taste receptor cells

“…One of these types of taste cells possesses synapses (type III cells, presynaptic cells), another expresses chemosensory transduction proteins (type II cells, light cells, taste receptor cells), and the third class expresses none of these properties (type I cells, dark cells) (Clapp et al, 2006;DeFazio et al, 2006;Tomchik et al, 2007;Yee et al, 2001). It has been stated that cells of the fish taste buds have morphological similarities to those of taste buds of rodent fungiform papillae (Murray, 1974); and a similar classification might be valid for fish taste buds (Reutter et al, 2000;Reutter and Hansen, 2005).…”