| Pondicherry shark | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Order: | Carcharhiniformes |
| Family: | Carcharhinidae |
| Genus: | Carcharhinus |
| Species: | C. hemiodon |
| Binomial name | |
| Carcharhinus hemiodon (J. P. Müller & Henle, 1839) |
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| Range of the Pondicherry shark | |
| Synonyms | |
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Carcharias hemiodon Valenciennes in J. P. Müller & Henle, 1839 * ambiguous synonym |
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The Pondicherry shark (Carcharhinus hemiodon) is a very rare and little-known species of requiem shark, family Carcharhinidae. It is mostly found in coastal and possibly brackish waters around the Indian subcontinent and Southeast Asia. This shark is small and stocky, with a rather long snout and a large first dorsal fin that is placed forward on the body and has a long rear tip. It is gray above and white below, with black-tipped pectoral, second dorsal, and caudal fins. Not seen since 1979, this species is listed as Critically Endangered by the International Union for Conservation of Nature (IUCN), and may be extinct.
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French zoologist Achille Valenciennes originally described the Pondicherry shark as Carcharias (Hypoprion) hemiodon, based on a 47 cm (19 in) long immature male from Pondicherry, India and three more paratypes from the same region.[2] He published his account in Johannes Peter Müller and Friedrich Gustav Jakob Henle's 1841 Systematische Beschreibung der Plagiostomen. In 1862, Theodore Gill proposed that this species be placed in a new genus, Hypoprionodon, based on the relative position of the dorsal and pectoral fins, though this was not generally accepted. Later authors have recognized Hypoprion as a synonym of Carcharhinus.[3] Another common name for this species is long nosed shark.[4] The evolutionary relationships of this species are uncertain. In 1988, Leonard Compagno placed it in an informal phenetic group also containing the smalltail shark (C. porosus), blackspot shark (C. sealei), spottail shark (C. sorrah), creek whaler (C. fitzroyensis), whitecheek shark (C. dussumieri), the Borneo shark (C. borneensis), and the hardnose shark (C. macloti).[5]
The Pondicherry shark was apparently broadly distributed in the Indo-Pacific region; it has been found at a handful of widely separated locations from the Gulf of Oman, India, and the Indonesian islands of Borneo and Java. There are also less reliable records from around the South China Sea, New Guinea, and northern Australia. It inhabits inshore waters and has been reported from brackish water in the lower stretches of the Hooghli and the Saigon River, though this remains to be verified.[3]
The Pondicherry shark is rather thick-bodied, with a moderately long, pointed snout. Each nostril is a broad slit preceded by a small, nipple-shaped flap of skin. The eyes are large and circular. The mouth is arched, without prominent furrows at the corners. There are 12–14 tooth rows on each side of both jaws, in addition to 1–2 small teeth at the symphysis (center). The teeth have a single narrow cusp, with those in the upper jaw wider and more angled than those in the lower jaw, and sometimes weakly serrated.[2][3]
The pectoral fins are short and falcate (sickle-shaped) with pointed tips, originating below the fourth gill slit. The first dorsal fin is tall, with a distinctive long free rear tip, and originates just behind the pectoral fin insertions. The second dorsal fin is long but low, and positioned about opposite the anal fin. There is a low ridge between the dorsal fins. The dermal denticles are oval and overlapping, with three (sometimes five) horizontal ridges leading to small marginal teeth. This species is plain gray above and white below, which extends in an obvious band onto the flanks. The pectoral, second dorsal, and caudal fins are tipped in black, while the other fins darken toward the margins.[2][3] The maximum size is uncertain due to a lack of large specimens, but probably does not much exceed 1 m (3.3 ft).[6]
Virtually nothing is known of the natural history of the Pondicherry shark.[2] Its diet likely consists of small bony fishes, cephalopods, and crustaceans.[4] It is presumably viviparous like other members of its family, with newborns measuring under 32 cm (13 in) long.[6] A known parasite of this species is the tapeworm Acanthobothrium paramanandai.[7]
Extremely rare, fewer than 20 specimens of the Pondicherry shark have been deposited in museum collections, most of which were collected prior to 1900. Despite detailed market surveys across much of its presumed range, the last confirmed sighting of the Pondicherry shark was in 1979 and it is feared to be extinct.[1] If it still survives, it would be heavily pressured by expanding, unregulated artisanal and commercial fisheries in the Indo-Australian region. The International Union for Conservation of Nature (IUCN) has listed it as Critically Endangered.[1]