Bramble shark

Appearance

The bramble shark has a thick, cylindrical body and a somewhat flattened head. The snout is blunt and shorter than the width of the mouth, with widely spaced nostrils that are preceded by small flaps of skin. The eyes lack nictitating membranes; the tiny spiracles are located well behind them. The wide, curved mouth bears very short furrows at the corners. There are 20–26 upper and 22–26 lower tooth rows; each tooth is knife-like, with a single main cusp and up to three cusplets on either side. There are five pairs of gill slits, with the fifth pair the longest.

The pectoral fins are short and angular, while the pelvic fins are long and relatively large. The dorsal fins are small, with the first dorsal fin origin lying behind the pelvic fin origins. There is no anal fin. The caudal peduncle is robust and lacks notches at the caudal fin origins. The asymmetrical caudal fin has an indistinct lower lobe and an upper lobe without a notch in the trailing margin.

The skin is covered by a layer of foul-smelling mucus several millimeters thick. The dermal denticles are scattered irregularly over the body and vary greatly in size, measuring up to 1.5 cm across. Each denticle is thorn-like in shape, with ridges radiating out from the central point over the base. As many as ten denticles may be fused together to form multi-pointed plates. The underside of the snout and the area around the mouth is densely covered by small denticles in sharks under 90 cm long; these denticles become larger and sparser in larger sharks. This species is brown to black above, with a metallic purplish hue, and paler below; some individuals have red or black blotches. There is a report of one specimen that had a greenish glow when freshly caught. The bramble shark may reach 3.1 m in length. The maximum weight on record is 200 kg for a 2.8 m long female.

Distribution

Records of the bramble shark are fairly rare and originate from widely scattered locations in tropical and temperate waters worldwide, save for the eastern Pacific Ocean. Most have come from the eastern Atlantic and western Indian Oceans, where its range extends from the North Sea and the British Isles to southern Mozambique, including the Mediterranean Sea. In the western Atlantic, this species is represented by a handful of specimens from Massachusetts, North Carolina, Louisiana, Tobago, Brazil, and Argentina. In the Indo-Pacific, it is known from Oman, India, southern Japan, southern Australia, New Zealand, and possibly Kiribati.

Behavior

Sluggish in nature, the bramble shark feeds on smaller sharks, bony fishes, and crabs. The large size of its pharynx, relative to its mouth, suggests that it may capture prey by suction. This species is aplacental viviparous; females have two functional ovaries and two uteruses. Recorded litter sizes have ranged from 15 to 52, and newly born pups have been estimated to measure 40–50 cm long. The dermal denticles in near-term embryos are underdeveloped, appearing as minute spines located within open pits in the skin. The size at sexual maturity is uncertain; the smallest known mature males and females are 1.5 m and 2.1 m long respectively.

Habitat

Found close to the sea floor, the bramble shark most commonly inhabits continental and insular shelves and slopes at depths of 400–900 m. However, it has been reported from as shallow as 18 m, in areas with upwellings of cold water, and from as deep as 1,214 m. At least in European waters, this species may migrate into shallower depths of 20–200 m during the summer.Sluggish in nature, the bramble shark feeds on smaller sharks, bony fishes, and crabs. The large size of its pharynx, relative to its mouth, suggests that it may capture prey by suction. This species is aplacental viviparous; females have two functional ovaries and two uteruses. Recorded litter sizes have ranged from 15 to 52, and newly born pups have been estimated to measure 40–50 cm long. The dermal denticles in near-term embryos are underdeveloped, appearing as minute spines located within open pits in the skin. The size at sexual maturity is uncertain; the smallest known mature males and females are 1.5 m and 2.1 m long respectively.