Species IUCN · Endangered (EN)

Porcupine Ray

Urogymnus asperrimus, (Bloch & Schneider, 1801)

marinebrackish

About Porcupine Ray

The porcupine ray (Urogymnus asperrimus) is a rare species of stingray in the family Dasyatidae. This bottom-dweller is found throughout the tropical Indo-Pacific, as well as off West Africa. It favors sand, coral rubble, and seagrass habitats in inshore waters to a depth of 30 m (100 ft). A large and heavy-bodied species reaching 1.2–1.5 m (3.9–4.9 ft) in width, the porcupine ray has a nearly circular, plain-colored pectoral fin disc and a thin tail without any fin folds. Uniquely within its family, it lacks a venomous stinging spine. However, an adult ray can still defend itself ably with the many large, sharp thorns found over its disc and tail.

The diet of the porcupine ray consists mainly of benthic invertebrates and bony fishes, which it digs up from the sea floor. It is aplacental viviparous, in which the developing embryos are nourished by histotroph ("uterine milk") produced by the mother. The porcupine ray has long been valued for its rough and durable skin, which was made into a shagreen leather once used for various utilitarian and ornamental purposes, such as to cover sword hilts and shields. It is caught incidentally by coastal fisheries. Because it must be handled carefully due to its thorns, its commercial significance is limited. Unregulated fishing has led to this species declining in many parts of its range, thus it has been listed as Endangered by the International Union for Conservation of Nature.

Appearance

The pectoral fin disc of the porcupine ray is evenly oval, almost as wide as long, and very thick at the center, giving it a domed appearance. The tip of the snout is rounded and barely protruding. The small eyes are closely followed by much larger spiracles. Between the narrow nostrils is a skirt-shaped curtain of skin; the posterior margin of the curtain is strongly fringed and overhangs the mouth. The mouth bears three to five papillae on the floor and prominent furrows at the corners. The area around the mouth, including the curtain, are heavily covered by more papillae. Around 48 tooth rows are found in either jaw. The teeth are small and flattened. Five pairs of gill slits are located on the underside of the disc.

Habitat

The porcupine ray is widely distributed, but uncommon compared to other stingrays that share its range. It is found all along the continental periphery of the Indian Ocean, from South Africa to the Arabian Peninsula to Southeast Asia to Ningaloo Reef off western Australia, including Madagascar, the Seychelles, and Sri Lanka; it has colonized the eastern Mediterranean Sea through the Suez Canal. In the Pacific Ocean, its range continues through Indonesia and New Guinea, north to the Philippines, east to the Gilbert Islands and Fiji, and south to Heron Island off eastern Australia. This species is also found in the eastern Atlantic Ocean off Senegal, Guinea, and Côte d'Ivoire. Bottom-dwelling in nature, the porcupine ray is found close to shore at depths of 1–30 m (3–100 ft). It inhabits sandy flats, coral rubble, and seagrass beds, often near reefs, and also enters brackish water.

Behaviour

The porcupine ray can sometimes be observed lying still on the bottom in the open or inside caves. It is known to form groups at Ningaloo Reef. Its diet consists primarily of sipunculids, polychaete worms, crustaceans, and bony fishes. When feeding, it plows deeply into the bottom, expelling excess sediment from its spiracles in a plume visible from a long distance away. Parasites documented from this ray include the tapeworm Rhinebothrium devaneyi, the nematode Echinocephalus overstreeti, and the capsalid monogeneans Dendromonocotyle urogymni and Neoentobdella baggioi. The porcupine ray is aplacental viviparous, with the developing embryos sustained to term by histotroph ("uterine milk") secreted by the mother. Mangrove forests serve as important habitat for juvenile rays. Males and females mature sexually at about 90 and 100 cm (35 and 39 in) across, respectively.

Humans & conservation

Despite not having a sting, the porcupine ray is capable of injuring humans with its many sharp thorns. It is reportedly bold and tolerant of being approached closely underwater. The tough, thorny skin of this ray, made into a form of leather called shagreen, had many historical uses. In particular, it was used to cover the hilts of various melee weapons, as its extremely rough texture prevented slippage during battle. For example, the Japanese deemed it the only species whose skin was acceptable for covering sword grips. The Malayans used it to cover shields. The skin was also used ornamentally, such as by the Chinese, who dyed it and ground down the thorns to yield a mottled pattern. The native inhabitants of Funafuti Atoll used dried portions of the ray's tail as a rasp-like tool.