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Round Stingray, Urobatis sp. (Description, feeding, reproduction, threats to human)

Photo credit: Glenda Vélez Calabria (Colombia)      Review: Abdel Rahman El Gamal

This photo was taken in mundo marino and te mostramos lo que pasa en el fondo, Colombia

Introduction: The round stingrays are which belong to the family “Urolophidae” and the genus “Urobatis” are cartilaginous fishes. It is also known as raya redonda (in Spanish). Due to its small size and large tail spine, the round stingray lacks commercial value and even considered a nuisance when they become entangled in the nets of shrimp trawlers are hence they are usually discarded.

Description: The round stingrays are distinguished by the presence of massive pectoral fins which join the boy to form a disc. The enlarged pectoral fins made it possible for these rays to swim by means of undulating or oscillating their fins. These rays have no anal fin. Instead, they have a whip-like tail with a long, thick, serrated stinging spine and with no caudal fin. The width of fin disc in females is larger compared to that in males with a maximum of about 30 cm to 25 cm respectively.

The eyes of the round sting rays are located on the upper side of the head while the nostrils, mouth, and gill slits are on the ventral side of the flattened body.

Distribution and habitat: This species inhabits tropical to warm-temperate waters at depths which could range from their common depth of less than 15 m up to much greater depths. While they prefer the soft-bottomed habitats (e.g. mud or sand), they also occur around rocky reefs. The species is endemic to the eastern North Pacific Ocean.

Feeding habits: The round stingray juveniles feed mostly on benthic invertebrates such as worms and small benthic crabs. As they grow, they feed on bivalve molluscs and polychaete worms. They use their pectoral disc and mouth in digging the pits to uncover buried preys. On the other hand, the round stingrays could be preyed upon by the elephant seal, the black sea bass and sharks.

Reproduction: The round stingray is ovoviviparous, whereas a female bears on the average 1-6 young that measure 6-8 cm at birth after a 3-months gestation period. The female is equipped by organs behind her eyes through which she emits a localized positive electric field, which serves to attract males towards copulation. 

Threats to humans: Numerous incidences of bathers who got stung by round stingrays when they accidentally step on the fish. The wound caused by its venomous spine can be quite painful, but is not fatal. The annual replacement of the stinging spine reduced the effectiveness of a program that targeted the clipping of the spines of the large stingray populations.

Round stingray

 

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