Taste bud form and distribution on lips and in the oropharyngeal cavity of cardinal fish species (Apogonidae, Teleostei), with remarks on their dentition.

Abstract

The oral dentition and type and number of taste buds (TB) on the lips and in the oropharyngeal cavity were compared by means of SEM in 11 species of cardinal fishes (Apogonidae) belonging to five genera. The occurrence of a dense cover of skin papillae on the lips of some species (e.g., Apogon frenatus), as well as differences in structure of vomer, tongue, and palatinum, expose additional morphological characters important for clarification of the taxonomy of this group of fishes. Differences are also revealed in the type of dentition, such as on the vomer and epi-hypopharyngeal bones. Strong and dense dentition of the anterior part of the oral cavity and a high number of TB on this site in species feeding on larger prey (e.g., Cheilodipterus spp) is compared to the relatively feeble jaw armor and richness of TB on the more pharyngeal site in species feeding on smaller prey (e.g., Apogon angustatus, A. frenatus). In addition to the three types of TB (Types I-III) previously described from various teleost fish, a fourth type (Type IV), comprising very small buds, was found in some cardinal fish (Apogon angustatus, A. frenatus). The various TB are distributed from the lips to the pharyngeal bones, on the breathing valves, tongue, palatinum, and pharyngeal bones; their number and type on the various sites differ in the different species. In all species studied the Types I and II TB, elevated above the surrounding epithelium, dominated the lips and anterior part of mouth, while Types III and IV, which end apically at the level with the epithelium, dominated the more posterior pharyngeal region. The highest number of TB, around 24,600, were found in Fowleria variegata, a typical nocturnal species, and the lowest in the diurnal and crepuscular Apogon cyanosoma (1,660) and Cheilodipterus quinquestriatus (2,400). Differences are also revealed in the type of dentition, such as on the vomer and epi-hypopharyngeal bones. The number of TB increased with growth of the fishes. The differences in the total number of TB and their distribution in the oropharyngeal cavity in the various species indicates possible different mechanisms of foraging and food-recognition.