Batoidea

Rays (Batoidea, Syn.: Rajomorphii) is a superorder in the class Cartilaginous fishes. With about 630 species, they represent more than half of the approximately 1170 cartilaginous fish species.

Rays live worldwide in all seas, some species also in the deep sea. Real rays (Rajidae) and electric rays are more species-rich in marine areas of temperate latitudes, the other families in tropical regions. Few species of the stingray family (Dasyatidae) also go into brackish and fresh water. In South America, apart from two exceptions, the Potamotrygonidae live in the major streams and rivers of the continent.

In the North Sea, the main members of the ray family (Rajidae) are the thornback ray (Raja clavata), the starry ray (Raja radiata), the smooth ray (Dipturus batis) and the cuckoo ray (Raja naevus). Other European species are the common stingray (Dasyatis pastinaca), the marbled stingray (Torpedo marmorata) and the Atlantic stingray (Torpedo nobiliana).

Features

Rays have a strongly flattened body and large pectoral fins, which are fused with the head. The shoulder girdle is ring-shaped and firmly or articulated to the spine. Some of the anterior vertebrae are fused to form a synarcuale. The mouth, nostrils, and five pairs of gill slits are on the flattened, usually pale underside. On the upper side are eyes and the valved spout holes through which water enters for breathing. The upper eyelid is firmly fused to the eyeball. The upper side is adapted to the particular habitat of the ray, so it can range from sand-colored speckled to black. The upper jaw, the palatoquadratum, is not connected to the neurocranium, but is only supported by the large hyomandibulare.

Movement sequence during undulation of the pectoral fins in a real ray (from bottom to top)

Nutrition

Most rays feed on hard-shelled invertebrates such as clams, crabs and echinoderms.