Читать книгу Clinical Guide to Fish Medicine - Группа авторов - Страница 39

The entire elasmobranch endoskeleton is cartilaginous. It is made up of a hyaline cartilage‐like core supported by mineralized tesserae (Omelon et al. 2014). Bone does exist in the form of teeth and denticles. While calcification can occur in the vertebrae and jaws, true bone is not found in those areas (Moss 1977). The centrum of the vertebral cartilage is used for aging elasmobranchs (Dean and Summers 2006). If elasmobranch cartilage is fractured, it does not heal fully but rather forms a fibrous “bandage” (Ashhurst 2004).

Many studies have examined elasmobranch skull anatomy, with particular reference to capturing prey. Three modes of prey capture occur (sometimes in combination): biting, ram feeding, and suction feeding (Wilga and Lauder 2004). Clinical relevance comes from the importance of the jaw protrusion capacity. Permanent jaw protrusion is reported to be associated with spinal deformity in sand tiger sharks (Carcharias taurus) (Anderson et al. 2012).

Figure A1.16 Ampullae of Lorenzini in a bamboo shark (Chiloscyllium sp.) (arrows) and across the ventrum of a blue‐spotted stingray (Neotrygon kuhlii).

Musculature is similar to teleosts, with red and white skeletal muscle (Figure A1.17). Most elasmobranchs are poikilothermic, but regional endothermy has been described in some lamniform sharks such as makos (Isurus spp.), white sharks (Carcharodon carcharias), salmon and porbeagle sharks (Lamna spp.), and thresher sharks (Alopias spp.) (Goldman 1997; Bernal et al. 2012; Shadwick and Goldbogen 2012).

Figure A1.17 Cross‐section through the peduncle of a blacktip reef shark (Carcharhinus melanopterus) showing red and white skeletal muscle.