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Starry Round Ray: Urotrygon asterias

Family: Urotrygonidae
Common names

Starry Round Ray, Blotchy Round Ray.

Binomial

Urotrygon asterias

Synonyms

Urotrygon chilensis

Identification

The Starry Round Ray was recently (2024) described on the basis of genetic differences between the northern and southern populations of the Chilean Round Ray (Urotrygon chilensis). Consequently, the following description is based on U. chilensis.

A medium-sized round stingray with a sub-circular disc that is wider than long; width 1.1-1.2 x length. Snout obtusely angular. Snout tip acutely pointed; more extended in mature males. Anterior margins of disc straight to mildly concave, apices broadly rounded. Disc roughened near centre line and on snout. Broken or continuous row of backwards slanting thorns on centre line from nape to tail sting. Pelvic fins broadly triangular with convex posterior margins, length slightly exceeding width.
Eyes large; orbit length 0.26-0.23 x snout length. Mouth weakly arched. Nasal curtain skirt-shaped. Nostrils narrowly oval.
Tail long and slender-based. Lateral skin folds absent. Tail length 53-56% of total length. Caudal sting slender, origin slightly anterior to mid-tail. Upper caudal lobe low and very long; 15-18% of total length. Posterior margin of caudal fin tightly rounded.

Colour

Dorsum highly variable. Often beige, pinkish, or dark brown, with irregular dark spots and blotches that may be scattered or so dense they form a solid mass centrally. Spots often extend onto pectoral fins and top of tail. Tail pale laterally. Ventrum pale, sometimes with subtle blotches. Caudal sting and upper lobe of caudal fin dark.

Size

Maximum total length 49.8cm (Ehemann et. al. 2024). Length at birth unknown.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarelt encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Conservation Status

NOT EVALUATED

The newly described Starry Round Ray has not been evaluated by the IUCN. It is one of the most abundant elasmobranch bycatch species Costa Rica and is common in Guatemala. It is generally discarded but may be retained for bait.
Starry Round Rays have a high biological productivity, but when grouped with Chilean Round Rays, they have undergone a population reduction of 20–29% over the last three generations (20 years) and are collectively listed as ‘Near threatened’.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
Habitat

Tropical/warm-temperate seas. Found on sandy or muddy substrates from very shallow bays to at least 20m (personal observation).

Distribution

Eastern Pacific. Found from the southern Sea of Cortez to Costa Rica.

Reproduction

Aplacental viviparous. Litter size unknown.

Diet

Diet consists mostly of small crustaceans, mollusks, polychaete worms and some fishes.

Behavior

Congregates (probably seasonally) in shallow bays. Camouflages itself under sand when resting.

Reaction to divers

Fairly easy to approach in shallow bays. Bolts once discovered but it is usually easy to pursue. Often found partially buried under sand. Harder to get close to or follow in deeper water.

Diving logistics

Probably fairly common at numerous beaches along the Pacific coast of Central America but rarely encountered around reefs.

I have encountered a few Starry round rays around Playa del Coco on the Pacific coast of Costa Rica, but they are far more common at Playa El Jobo; about 60km north by car. There are no dive shops in El Jobo but the rays congregate in very shallow water so it is easy to see them while snorkelling.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 080

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 078

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 077

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 074

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A small male ray pursuing a larger female. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 067

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A small male ray pursuing a larger female. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarelt encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 057

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarelt encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarelt encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 048

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarelt encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarelt encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
View Larger

Starry Round Ray 043

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarelt encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarelt encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
View Larger

Starry Round Ray 041

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarelt encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarely encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
View Larger

Starry Round Ray 024

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarely encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarely encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 023

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarely encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A juvenile from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 017

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A juvenile from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A juvenile from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 013

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A juvenile from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 008

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A gravid female from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarely encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
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Starry Round Ray 007

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarely encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarely encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.
View Larger

Starry Round Ray 004

Starry Round Ray - Urotrygon asterias. Recently separarted from the Chilean Round Ray Urotrygon chilensis. Aka blotched round ray or blotched stingray. A common but rarely encountered ray from the eastern tropical Pacific. Playa El Jobo, Guanacaste, Costa Rica.

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Similar species

Chilean Round Ray (Urotrygon chilensis) Difficult to distinguish in the field, except by more southerly range from Ecuador to Chile.

Rogers' Round Ray

Rogers Round Ray Quite similar but distinguishable by much sparser, smaller dark spots and proportionately wider disc with more concave anterior margins.

Cimar Round Ray Similarly patterned with dark spots and blotches, but distinguishable by proportionately smaller eyes, rounder disc with rough skin, and tail shorter than disc.