Читать книгу Clinical Guide to Fish Medicine - Группа авторов - Страница 44

The types of teeth or dental plates are dictated by the feeding strategy (biting, crushing, shearing, filter feeding, etc.) and can often be used to speciate animals (Kemp 1999). The teeth or plates erupt and roll out continuously, with the caudal‐most gradually replacing the front; this is polyphyodont dentition. Teeth are lyodont (embedded in the oral mucosa, not ankylosed to the jaw) and consist of dentine and enameloid. Tooth replacement rates vary among species, from 8 to 10 days per row up to 5 weeks per row (Motta 2004). If animals that normally eat crustaceans and hard‐bodied prey are not provided with these foodstuffs, overgrowth of the plates can occur. Gingival hyperplasia and neoplasia have been described in sand tigers (Carcharias taurus) (Borucinska et al. 2004).

Denticles are present in the pharynx of most sharks (except carpet sharks, Orectolobiformes) and some other elasmobranchs such as guitarfish (Rhinobatidae). This may decrease drag for ram ventilators, prevent trauma from prey, and improve predation success (Atkinson and Collin 2012).