Читать книгу Clinical Guide to Fish Medicine - Группа авторов - Страница 82

These animals include the typical stingrays. These show dorsoventral compression with enlarged pectoral fins that are continuous with their heads. The five gill openings are ventral. Eyes and spiracles are on the dorsal surface and water is pulled in through the spiracles for respiration. The jaws are protrusible and do not articulate with the neurocranium (Nelson et al. 2016). There is no nictitating membrane and the cornea attaches directly to the skin around the eyes. The cranial vertebrae are fused with the pectoral girdle (synarcual). There is no anal fin. Most have one or more venomous spines (barbs) along the tail. Some key aquarium families are listed below.

 Aetobatidae, Myliobatidae, Mobulidae, Rhinopteridae: eagle rays, mobulids, cownose rays. These have a small dorsal fin on the base of the tail. The head is elevated above the pectoral fins and the eyes and spiracles are lateral on head. Tooth‐plates are made up of six‐sided teeth in a horizontal arrangement. They are capable of leaping into the air. The mobulids, which include manta rays (Manta spp.), have cephalic lobes that are cranial extensions of the pectoral fins and assist in feeding. These animals also have gill rakers. Mobulids lack venomous barbs.

 Dasyatidae: whiptail stingrays. These inhabit freshwater and saltwater habitats. They have a long and slender tail.

 Potamotrygonidae: river stingrays. These are all freshwater species and show a reduced rectal gland. Their venom is more potent than saltwater species.