Zebra Shark

The genus name is derived from the Greek stego meaning "covered", and stoma meaning "mouth". The specific epithet fasciatum means "banded", referring to the striped pattern of the juvenile. The juvenile coloration is also the origin of the common name "zebra shark". The name "leopard shark" is sometimes applied to the spotted adult, but that name usually refers to the houndshark Triakis semifasciata, and is also sometimes used for the tiger shark (Galeocerdo cuvier). Both S. fasciatum and S. varium are currently in usage for this species; A taxonomic review in 2019 instead argued that S. tigrinum is its valid name. This name was omitted in Compagno's review in 1984, possibly due to confusion over its year of description (in a publication in 1941, Fowler mistakenly listed it as being described in 1795). Squalus tigrinus was described by Forster in 1781, two years before Squalus fasciatus was described by Hermann. Consequently, the former and older is the valid name (as Stegostoma tigrinum), while the latter and younger is its junior synonym. As the name proposed by Forster in 1781 has been used in tens of publications since 1899, it is not a nomen oblitum.

There is robust morphological support for the placement of the zebra shark, the whale shark (Rhincodon typus), and the nurse sharks (Ginglymostoma cirratum, Nebrius ferrugineus, and Pseudoginglymostoma brevicaudatum) in a single clade. However, the interrelationships between these taxa are disputed by various authors. Compagno (1988) suggested affinity between this species and either Pseudoginglymostoma or a clade containing Rhincodon, Ginglymostoma, and Nebrius.

The zebra shark occurs in the tropical waters of the Indo-Pacific region, from South Africa to the Red Sea and the Persian Gulf (including Madagascar and the Maldives), to India and Southeast Asia (including Indonesia, the Philippines, and Palau), northward to Taiwan and Japan, eastward to New Caledonia and Tonga, and southward to northern Australia.

During the day, zebra sharks are sluggish and usually found resting on the sea bottom, sometimes using their pectoral fins to prop up the front part of their bodies and facing into the current with their mouths open to facilitate respiration. Reef channels are favored resting spots, since the tightened space yields faster, more oxygenated water. They become more active at night or when food becomes available. Zebra sharks are strong and agile swimmers, propelling themselves with pronounced anguilliform (eel-like) undulations of the body and tail. In a steady current, they have been seen hovering in place with sinuous waves of their tails. The zebra shark feeds primarily on shelled molluscs, though it also takes crustaceans, small bony fishes, and possibly sea snakes. The slender, flexible body of this shark allows it to wriggle into narrow holes and crevices in search of food, while its small mouth and thickly muscled buccal cavity allow it to create a powerful suction force with which to extract prey. This species may be preyed upon by larger fishes (notably other, much larger sharks) and marine mammals. Known parasites of the zebra shark include four species of tapeworms in the genus Pedibothrium.

Zebra sharks are usually solitary, though aggregations of 20–50 individuals have been recorded. Off southeast Queensland, aggregations of several hundred zebra sharks form every summer in shallow water. These aggregations consist entirely of large adults, with females outnumbering males by almost three to one. The purpose of these aggregations is yet unclear; no definite mating behavior has been observed between the sharks. There is an observation of an adult male zebra shark biting the pectoral fin of another adult male and pushing him against the sea floor; the second male was turned on his back, and remained motionless for several minutes. This behavior resembles pre-copulatory behaviors between male and female sharks, and in both cases the biting and holding of the pectoral fin has been speculated to relate to one shark asserting dominance over the other.

The courtship behavior of the zebra shark consists of the male following the female and biting vigorously at her pectoral fins and tail, with periods in which he holds onto her pectoral fin and both sharks lie still on the bottom. On occasion this leads to mating, in which the male curls his body around the female and inserts one of his claspers into her cloaca. Copulation lasts for two to five minutes. The zebra shark is oviparous, with females laying large egg capsules measuring long, wide, and thick. The egg case is dark brown to purple in color, and has hair-like fibers along the sides that secure it to the substrate. In captivity, the eggs hatch after four to six months, depending on temperature. An additional study has observed parthenogenesis in females regardless of sexual history.

]] Docile and slow-moving, zebra sharks are not dangerous to humans and can be easily approached underwater. However, they have bitten divers who pull on their tails or attempt to ride them. As of 2008 there is one record of an unprovoked attack in the International Shark Attack File, though no injuries resulted. Zebra sharks are highly susceptible to localized depletion due to their shallow habitat and low levels of dispersal between populations, and market surveys suggest that they are much less common now than in the past. They are also threatened by the degradation of their coral reef habitat by human development, and by destructive fishing practices such as dynamiting or poisoning. As a result, the IUCN Red List has this species categorized as Endangered.