Smoothtooth blacktip shark

Smoothtooth blacktip shark
Conservation status
	; Endangered (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Order:	Carcharhiniformes
Family:	Carcharhinidae
Genus:	Carcharhinus
Species:	C. leiodon
Binomial name
	Carcharhinus leiodon; Garrick, 1985
	Range of the smoothtooth blacktip shark

The smoothtooth blacktip shark (Carcharhinus leiodon) is a

type specimen caught from the Gulf of Aden, off eastern Yemen, and a handful of additional specimens caught from the Persian Gulf, off Kuwait

. Reaching 1.3 m (4.3 ft) in length, this species has a stocky greenish-colored body, a short snout, and black-tipped fins. It can be distinguished from similar species by its teeth, which are narrow, erect, and smooth-edged.

Little is known of the smoothtooth blacktip shark's natural history; it likely inhabits shallow waters and feeds on small

habitat degradation

within its range.

Taxonomy and phylogeny

The first known specimen of the smoothtooth blacktip shark was a 75-cm-long, immature male caught by Wilhelm Hein in 1902 and deposited at the

ichthyologist Jack Garrick in a National Oceanic and Atmospheric Administration technical report. He gave it the specific epithet leiodon, from the Greek leios meaning "smooth", and odon meaning "tooth".^[3] This species was known only by the single specimen until 2008, when fishery surveys in Kuwait uncovered several more specimens.^[2]

Based on

molecular phylogenetic techniques on mitochondrial DNA sequences, Alec Moore and colleagues reported in 2011 that this species is closely related to the graceful shark, the blacktip shark, and the Australian blacktip shark (C. tilstoni).^[2]

Description

Superficially, the smoothtooth blacktip shark resembles the blacktip reef shark (C. melanopterus). It is rather robust in build, with a short and blunt snout. The large nostrils are preceded by well-developed, triangular flaps of skin. The small, circular eyes are equipped with nictitating membranes. The mouth forms a wide arch and has very short furrows at the corners. Sixteen upper and 14–15 lower tooth rows are on either side, along with two or three small teeth at the symphysis (center) of either jaw. The teeth are distinctive in shape, having narrow, upright cusps without serrations; finetooth sharks and juvenile spinner sharks are the only other members of Carcharhinus with similar teeth. The five pairs of gill slits are long.^[2]^[3]

The fairly long and pointed

dermal denticles are slightly overlapping and bear three prominent horizontal ridges leading to three or five marginal teeth. This species is greenish-yellow to greenish-gray above, sometimes with a scattering of tiny dark dots. The underside is white, which extends in a pale band onto the flanks. All the fins have sharply defined black tips, and a broad, dark midline stripe runs from the second dorsal fin base to the tip of the upper caudal fin lobe. The largest recorded specimen is 1.2 m (3.9 ft) long.^[2]^[3]

Distribution and habitat

The smoothtooth blacktip shark has only been recorded from eastern Yemen and Kuwait, some 3,000 km (1,900 mi) apart. These two locations differ markedly: the Gulf of Aden near Yemen is over 2.5 km (1.6 mi) deep with a narrow

speedboat fishers, this shark can be supposed to inhabit shallow, coastal waters. Still, these waters encompass a range of habitats from estuaries to coral reefs, thus the habitat requirements of the smoothtooth blacktip shark remain largely unknown.^[2]

Biology and ecology

Considering its resemblance to the blacktip reef shark, the smoothtooth blacktip shark may play an equivalent shallow-water

viviparous like all other Carcharhinus species, with the developing young sustained to term by a placental connection to the mother.^[5] Judging from the available specimens, males reach sexual maturity at some point between 0.9 and 1.2 m (3.0 and 3.9 ft) long.^[2]

Human interactions

Prior to the finding of additional specimens in Kuwait, the

Gillnet and other fisheries off Kuwait are known to take the smoothtooth blacktip shark as bycatch, while intensive Yemeni and Somalian shark fisheries operate in the Gulf of Aden. The status of the Yemen subpopulation is uncertain because no further specimens have been recorded since the original over a century ago.^[2]