Читать книгу Clinical Guide to Fish Medicine - Группа авторов - Страница 56

Sturgeons and paddlefish are large, long‐lived, freshwater fish. They have a heterocercal fin with a large dorsal lobe similar to sharks and a reduced or absent preopercle (part of the operculum) such that some of the gills are grossly visible. They have spiracles, similar to some elasmobranchs. The skeleton is mostly cartilaginous. They have a spiral valvular intestine. Gills are often brown in color and this should not be mistaken for methemoglobinemia. Paddlefish have gill rakers. Their skin is largely scaleless although sturgeons have solid dermal plates. They have a prominent pneumatic duct to the swim bladder, so care should be taken when passing a gavage tube. They have a single, simple swim bladder that is asymmetrical and positioned on the right side of the body (Helfman et al. 2009; Nelson et al. 2016).