Porcupine Ray.

The porcupine ray, Urogymnus asperrimus, is a species of stingray in the family Dasyatidae, found in shallow coastal waters throughout the tropical Indo-Pacific and off West Africa. Growing over 1 m (3.3 ft) across, the porcupine ray has a thick, rounded pectoral fin disk with small eyes. Unlike other stingrays, it does not have a venomous spine on its tail. Its common name comes from the numerous large thorns covering the back and tail of adult individuals. Little is known of its biology; it feeds on benthic invertebrates and is likely ovoviviparous as with other members of its family. Historically, the porcupine ray was valued as a source of shagreen; its tough, spiny skin was used to cover shields, hilts, and other items. In addition, its tail was used as a rasping tool. The porcupine ray is declining in numbers throughout its range from human exploitation and habitat degradation, and has been assessed as Vulnerable by the World Conservation Union.

Taxonomy

The porcupine ray was originally described as Raja asperrima by German naturalists Marcus Elieser Bloch and Johann Gottlob Schneider, in Systema Ichthyologiae (1801), based on a partial dried skin from Mumbai, India. In the same work they also described a West African form, Raja africana, which is now regarded to be the same species. In 1837, Johannes Peter Müller and Friedrich Gustav Jakob Henle moved this species into its own genus, Urogymnus. The specific epithet asperrimus is Latin for "roughest". Other common names include black spotted ray, rough-skinned ray, roughback stingaree, solanders ray, and thorny ray.

Distribution and habitat

The porcupine ray is widely distributed in the Indian and Pacific Oceans, from South Africa and Madagascar to the Arabian Peninsula and the Indian subcontinent, to Southeast Asia, the Philippines, and Indonesia, to as far east as New Guinea, Australia, and Fiji. It is also present off the coasts of Senegal, Guinea, and Côte d'Ivoire, and has colonized the eastern Mediterranean Sea through the Suez Canal. This species is typically encountered on sandy flats or coral rubble near reefs, or inside caves. It also ventures into brackish environments.

Description

A large, heavy-bodied fish, the porcupine ray grows to 2.2 m (7.2 ft) long and over 1 m (3.3 ft) across. Its pectoral fin disk is rounded and very thick, slightly longer than wide, with a blunt-tipped snout. The eyes are tiny and smaller than the spiracles. The mouth is small, containing around 48 tooth rows in either jaw, and 3–5 papillae on the floor. The tail is thin and no longer than the disk, with no fin fold or stinging spine. The dorsal surface of adults is covered with heart-shaped tubercles interspersed with large, sharp thorns, with dense patches of smaller, flattened denticles on the center of the disk and the tail. This species is light gray above and white below, darkening towards the tip of the tail.

Biology and ecology

Porcupine rays are relatively uncommon compared to other stingray species that share its range. They feed primarily on sipunculids, polychaete worms, and crustaceans. Known parasites of this species include the tapeworm Rhinebothrium devaneyi, the nematode Echinocephalus overstreeti, and the monogeneans Dendromonocotyle urogymni and Neoentobdella baggioi. Virtually nothing is known of the porcupine ray's life history; it is presumably ovoviviparous like other stingrays, with the developing embryos being sustained on yolk and later histotroph ("uterine milk") secreted by the mother.

Human interactions

Despite not having a stinging spine, the porcupine ray is capable of injuring humans with its many sharp thorns. This species is believed to be of limited commercial importance on virtue of being difficult to handle; the meat, skin, and cartilage are of value. The skin in particular is prized for making shagreen, a type of leather. Historically, it was often used to cover shields and the hilts of various weapons, as its extremely rough texture prevented slippage during battle. In Japan, the porcupine ray was the only species whose skin was deemed acceptable for covering sword hilts. The Chinese also utilized porcupine ray shagreen ornamentally, by grinding down the thorns to yield a mottled pattern. The native inhabitants of Funafuti Atoll used dried portions of the porcupine ray's tail as a rasp-like tool.

In modern times, porcupine rays are mostly taken as bycatch in demersal tangle net operations. These fisheries are largely unregulated and have resulted in this species declining or vanishing from the Bay of Bengal, the Gulf of Thailand, and likely elsewhere in its range. Additional threats to porcupine ray populations include habitat degradation from coastal development, and depletion of its food supply from overfishing. The World Conservation Union has assessed this species as Vulnerable; it is not the target of any conservation measures.