Starry Round Ray, Urotrygon asterias

Starry Round Ray, Urotrygon asterias. Fish provided by the commercial fishermen of Bahía Kino, Sonora, March 2015. Total Length: 39 cm (15 inches). Disc: 22 cm (8.6 inches) x 23 cm (9.1 inches). Tail: 17 cm (6.7 inches). Photograph and identification courtesy of Maria Johnson, Prescott College Kino Bay Center, Kino Bay, Sonora.

Starry Round Ray, Urotrygon asterias. Underwater photographs taken in Zihuantanejo Bay, Guerrero, March 2018. Photographs courtesy of Maude Jette, Dive Zihuantanejo, www.Divezihuantanejo.com.

Note: the identification of these animals with 100% certainty requires a hands on examination with an up-close view of the spinage of the back and tail which is not normally possible while viewing and photographing such species underwater. The identifications made above should be viewed accordingly for which I would estimate a greater than 90% that each has been identified correctly.

The Starry Round Ray, Urotrygon asterias, is a member of the American Round Stingray or Urotrygonidae Family, and is known in Mexico as raya redonda. Globally, there are thirteen species in the genus Urotrygon, of which five are found in Mexican waters, all in the Pacific Ocean.

The Starry Round Ray has a wide oval disc-shaped body with a straight front margin, that are slightly wider than they are long with a slightly projecting snout. They are a uniform gray, gray-brown or tan color with irregular dark gray or black spots. Their underside is off-white with a brown border. Their pectoral fins are continuous around the head. Their head has large eyes and spiracles on top and the mouth, nostrils, and gill slits are located on the ventral side. Their tail is slender and about equal to the disc length with one large venomous spine located mid-tail. They have denticles scattered over the entire disc with patches between their eyes, on the sides below their eyes, along the back, and on top of and on the sides of their tail. They have one row of irregularly shaped thorns on the mid-back and tail.

The Starry Round Ray is a demersal species that resides over and within coastal sandy and muddy bottoms at depths up to 61 m (200 feet). They reach a maximum of 42 cm (17 inches) in total length with a maximum disc width of 26 cm (10 inches). They seek food by stirring bottom sediment with their pectoral fins to dislodge small crustaceans, small fish, mussels, and worms on which they feed. Reproduction occurs via internal fertilization with embryos developing via aplacental vivparity with a gestation period of three months. Their pups are born alive and resemble miniature adults that are independent at birth. The Starry Round Ray is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Starry Round Ray is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from Magdalena Bay, Baja California Sur, northward along the central and northwest coasts of Baja.

The Starry Round Ray can be confused with the Panamic Stingray, Urotrygon aspidura, the Spiny Stingray, Urotrygon munda, and the Thorny Stingray, Urotrygon rogersi, however, both lack the spotting pattern on their backs found in the Blotched Stingray.

From a conservation perspective the Starry Round Ray is currently classified as Data Deficient. They are very rare, seldom seen by humans, and of limited interest to most.