ABSTRACT
Fish employ their oral taste buds (TB) to screen and, subsequently, either reject food particles or accept and then swallow them (Pavlov and Kasumyan, 1998; Kasumyan and Prokopova, 2003; Hansen and Reutter, 2004; Fishelson, 2005a, b). The TB are distributed throughout the skin, but are especially concentrated along various protrusions around the mouth opening and in the oropharyngeal cavity (Whitear, 1971; Kapoor et al., 1975; Gomahr et al., 1992; Hara, 1992; Hansen and Reutter, 2004). As described by Schulte and Holl (1972) and observed during the present study (Fishelson, pers. observ.), some TB are even found on the cirri growing over the nuchal openings as well as supraocularly. Until recently, TB had been studied in catfish (Reutter, 1978; Kapoor and Finger, 2003; Kiyohara and Tsukahara, 2005), rainbow trout (Ezeasor, 1982), minnow (Kiyohara et al., 1980), and lungfish (Reutter, 1991). Several recent
studies compared the TB distribution in groups of species from the same family: e.g., on several flatfishes (Livingstone, 1987), on cardinal fishes (Fishelson and Delarea, 2004), on blennies and gobies (Fishelson et al., 2004), and on various cichlid fishes (Fishelson, 2005a, b). The form and activity of TB have also been reviewed in several books (Hara, 1992; Finger et al., 2000; Doty, 2003), with the most recent one being Fish Chemosenses, edited by Reutter and Kapoor (2005). All these studies revealed two important phenomena: first, TB distribution is speciesspecific and can serve as a specific marker of microadaptation (Fishelson and Delarea, 2004; Reutter and Hansen, 2005; Fishelson, 2005b; Gon et al., 2007); second, this distribution often shows a unique adaptation to the dentition pattern and the type of food and feeding regime of the fish. Various studies have shown that three types of TB are found in the oral cavity (OC) of fish: type I, situated on small papillae or hillocks, 40-60 mm in diameter and 80-100 mm high, rising above the surrounding epithelium; type II, closely resembling type I, but less elevated; and type III, which does not protrude and whose exposed apical ends are level with the surrounding epithelium. Starting with the studies of Murray and Murray (1970), it became evident that all three TB-types possess two kinds of elongated sensory cells, either dark or pale, bearing sensory protrusions of various dimensions at their apical ends (Reutter and Hansen, 2005). From these, the TB signals are transmitted via the sensory parts of the facial (VII), glossopharyngeal (IX), and vagal (X) nerves to the brain centers situated in the medulla oblongata (Fishelson, 2005b; Reutter and Witt, 2005). The present study compares the distribution and numbers of TB relative to dentition in the OC in selected species of the families Labrisomidae, Clinidae, Blenniidae, Tripterygiidae and Dactyloscopidae, together forming a part of the suborder Blennioidei.
