diamond stingray

The diamond stingray attains a disc width of 1 m (3.3 ft) or possibly 1.2 m (3.9 ft); females grow larger than males. Its pectoral fin disc is rhomboid in shape, slightly wider than long, with angular outer corners and subtly convex margins. The snout is blunt-angled and non-projecting. The eyes are fairly large and immediately followed by the spiracles (paired respiratory openings). The mouth is strongly curved, containing 21–37 upper tooth rows and 23–44 lower tooth rows; the teeth are small and blunt, and arranged into flattened surfaces. Three or five papillae (nipple-like structures) are found in a row across the floor of the mouth. The whip-like tail generally measures up to one and half times the length of the disc, and bears one (more if replacements have grown in) long, slender, serrated spine on the upper surface, closer to the base than the tip. Behind the spine, there are long dorsal and ventral fin folds that rise gradually, reaching a relatively high apex before sloping down abruptly. The presence of the upper fin fold separates this species from the similar longtail stingray (D. longa), which shares most of its range. However, the tail is often damaged, in which case differentiating the two species in the field becomes all but impossible. …

The diamond stingray is found in the eastern Pacific Ocean from southern California to northern Chile, as well as around the Galápagos and Hawaiian Islands; it is very abundant around Baja California and in the Gulf of California. At the northern and southern extremes of its range, it is generally only present during periods of suitably warm water brought about by El Niño. There is a record of this ray from off British Columbia, which is unconfirmed and would be highly anomalous as it is known to be a tropical and warm-temperate species. A bottom-dwelling inhabitant of inshore waters, the diamond stingray favors sandy or muddy bottoms, often near rocky reefs or kelp forests. Off southern California, it usually occurs from the intertidal zone to a depth of 7 m (23 ft) during the summer, shifting to depths of 13–18 m (43–59 ft) during late fall and winter. For unknown reasons, it prefers to overwinter in kelp forests rather than sandy flats. Off Chile, the diamond stingray occurs at a similar depth of 3–30 m (10–100 ft). On the other hand, this species has been reported from as far down as 355 m (1,165 ft) off Hawaii, which if accurate would suggest that it utilizes a much greater range of depths than previously realized.

The diamond stingray is most active at night, spending much of the day buried in sand with only its eyes protruding. When foraging for food, it may be solitary but more commonly forms groups numbering up to the hundreds. There is strong segregation by sex and age. This species feeds on crustaceans, molluscs, and other invertebrates, as well as small bony fishes; its powerful jaws and molar-like teeth allow it to crush hard-shelled prey. It mainly targets burrowing organisms, but may also take prey exposed on the bottom. There is a record of a female 69 cm (27 in) across, that had gorged herself on at least 30 small crabs. In the Bahía Magdalena lagoon complex, Baja California Sur, its most important source of food are pea crabs, followed by the razor clam Solyema valvulus, and then polychaete worms. The typical hunting strategy of the diamond stingray is to cruise just above the sea floor, landing atop any prey encountered. It then quickly levers its body up-and-down with its disc, producing negative pressure to extract the prey from its burrow. This ray has also been known to excavate large pits by undulating its disc and spitting jets of water, so as to uncover buried prey. …