Tawny nurse shark

The tawny nurse shark was first described by French naturalist René-Primevère Lesson as Scyllium ferrugineum, based on a long specimen from New Guinea. His short account was published in 1831 in . A more detailed description, along with an illustration, was published by German naturalist Eduard Rüppell in 1837 as Nebrius concolor, based on a specimen from the Red Sea. Both names were retained, often in separate genera (Ginglymostoma and Nebrius respectively), until they were synonymized by Leonard Compagno in 1984. Compagno recognized that the tooth shape differences used to separate these species were the result of differences in age, with N. concolor representing younger individuals. The genus name Nebrius is derived from the Greek word nebris or nebridos, meaning the skin of a fawn. The specific epithet ferrugineus is Latin for "rust-colored". Other common names for this species include giant sleepy shark, Madame X (a name coined by the shark fisherman Norman Caldwell in the 1930s for the then-unidentified Australian specimens), nurse shark, rusty catshark, rusty shark, sleepy shark, spitting shark, and tawny shark. Based on morphological similarities, Nebrius is believed to be the sister genus of Ginglymostoma, with both being placed in a clade that also contains the short-tail nurse shark (Pseudoginglymostoma brevicaudatum), the whale shark (Rhincodon typus), and the zebra shark (Stegostoma tigrinum). ==Distribution and habitat==

The tawny nurse shark is widely distributed in the Indo-Pacific region. In the Indian Ocean, it is found from KwaZulu-Natal, South Africa northward to the Red Sea, Persian Gulf and India, including Madagascar, Mauritius, the Chagos Archipelago, the Seychelles, and the Maldives. In the western Pacific, it occurs from southern Japan and the coast of China to the Philippines, Southeast Asia, and Indonesia, to as far south as the northern coast of Australia. In the central Pacific, it has been reported from off New Caledonia, Samoa, Palau, the Marshall Islands, and Tahiti. An inshore species, the tawny nurse shark inhabits continental and insular shelves over sandy flats or beds of seagrass, as well as along the outer edges of coral or rocky reefs. This shark may be found from the surf zone, often in water barely deep enough to cover its body, to a maximum depth of on coral reefs; it is most common at a depth of . Young sharks are generally found in the shallow areas of lagoons, while adults may be encountered across a variety of habitats. ==Description==

The tawny nurse shark grows to a maximum length of . ==Biology and ecology==

With a more streamlined form than other nurse sharks, the tawny nurse shark is believed to be a less benthic, more active swimmer. The characteristics of its body, head, fins, and teeth are comparable to other active reef sharks sharing its range, such as the sicklefin lemon shark (Negaprion acutidens). Tawny nurse sharks are primarily nocturnal, though they are said to be active at all hours off Madagascar, and in captivity they will become diurnally active if presented with food. During the day, groups of two dozen or more sharks can be found resting inside caves and under ledges, often stacked atop one another. Individual sharks have small home ranges that they consistently return to each day. Feeding The tawny nurse shark may be one of the few fishes specializing in preying on octopus. Other known food items include corals, sea urchins, crustaceans (e.g. crabs and lobsters), squid, small fishes (e.g. surgeonfish, queenfish, and rabbitfish), and the occasional sea snake. Hunting tawny nurse sharks swim slowly just above the sea floor, poking their heads into depressions and holes. When a prey item is found, the shark forcefully expands its large, muscular pharynx, creating a powerful negative pressure that sucks the prey into its mouth. The tawny nurse shark is the only carpet shark in which there is oophagy: once the developing embryos exhaust their supply of yolk, they gorge on eggs produced by the mother and acquire the distended abdomen characteristic of such oophagous embryos. Unlike in mackerel sharks, the eggs consumed by the embryos are large and shelled rather than small and undeveloped. There is no evidence of sibling cannibalism as in the sand tiger shark (Carcharias taurus). Various authors have reported the length at birth anywhere from , with the discrepancy possibly reflecting geographic variation. Although females release up to four fertilized eggs into each uterus, the very large size of the newborns suggest that the litter size may be as few as one or two. In one examined female that had two embryos sharing a single uterus, one embryo was much smaller and thinner than the other, implying that competition may eliminate the additional siblings. Males attain sexual maturity at a length of , and females at a length of . ==Human interactions==

Encounters with tawny nurse sharks underwater indicate a more docile demeanor than the similar nurse shark; usually divers are able to approach the sharks closely and even touch and play with them without incident. However, this species has been infrequently provoked into biting, and merits respect due to its strength, small but sharp teeth, and extremely powerful jaws. Tawny nurse sharks are favored attractions for ecotourist divers off Thailand, the Solomon Islands, and elsewhere. This species also adapts well to captivity and is displayed in public aquaria in Europe, the United States, Okinawa, and Singapore, where they may become tame enough to be hand-fed. The tawny nurse shark is taken by commercial fisheries operating throughout its range, including off Pakistan, India, Thailand, and the Philippines; an exception is in Australian waters, where it is only taken in small numbers as bycatch. This shark is caught using demersal trawls, floating and fixed bottom gill nets, and on hook-and-line. The meat is sold fresh or dried and salted, the fins are used for shark fin soup, and the offal processed into fishmeal. In addition, the liver is a source of oil and vitamins, and the thick, tough skin is made into leather products. Off Queensland, Australia, the tawny nurse shark is valued by big-game anglers. When hooked, large individuals are tenacious opponents and are difficult to subdue due to their habit of spinning. They are also capable of spitting a powerful jet of water into the faces of their captors, making grunting noises in between jets (making the tawny shark one of the few species of sharks to produce a noise);whether this is a deliberate defensive behavior is uncertain. The International Union for Conservation of Nature (IUCN) has assessed the tawny nurse shark as Vulnerable worldwide, as it faces heavy fishing pressure and its low reproductive and dispersal rates limit the ability of over-exploited populations to recover. Furthermore, this shark's inshore habitat renders it susceptible to habitat degradation, destructive fishing practices (e.g. poisons and explosives, especially prevalent off Indonesia and the Philippines), and human harassment. Localized declines or extirpations of the tawny nurse shark have been documented off India and Thailand. Off Australia, this species has been assessed as of Least Concern, as there it is not targeted by fisheries. ==References==