Frilled shark, the mystery of the abyss



by LORENZO CIOTTI

Frilled shark, the mystery of the abyss

Rarely spotted, the frilled shark captures prey by bending its body and lunging forward like a snake. The extremely flexible jaws allow them to swallow large prey, while the rows of small sharp teeth prevent them from escaping.

It feeds mainly on cephalopods but also consumes bony fish and other small sharks. This species is aplacental ovoviviparous: embryos are born from eggs that hatch inside the mother's uterus, and finish development by consuming mainly the reserves of their yolk.

The frilled shark has the longest gestation period of any vertebrate - it can last three and a half years. 2 to 15 young are born at a time, and there is no distinct breeding season. This species lives on the outer zone of the continental shelf and the upper continental slope, usually near the bottom.

It lives up to 1300 meters deep, although in Suruga Bay, Japan, it is more common at depths of 50-200 meters. It has numerous primitive characters, which earned it the name of living fossil. Its body, which can reach 2 meters in length and is dark brown in color, resembles that of an eel with its dorsal, pelvic and anal fins set far back.

The frilled shark has a very large but discontinuous range. It is found sporadically in the Atlantic and Pacific oceans. In the eastern Atlantic, it lives off northern Norway, north of Scotland and west of Ireland, and from France to Morocco, including the waters off Madeira and Mauritania.

In the central Atlantic, it has been fished in several places along the mid-Atlantic ridge, from the north of the Azores to the Rio Grande chain, off southern Brazil, as well as on the Vavilov range, off West Africa. In the eastern Atlantic, it has been observed off New England, Georgia and Suriname.

In the western Pacific, its presence has been found southeast of Honshu in Japan, Taiwan, offshore New South Wales and Tasmania in Australia and around New Zealand. In the central and eastern Pacific, it has been observed off Hawaii, California and northern Chile.

The frilled shark inhabits the outer zone of the continental shelf and the upper half of the continental slope, and appears to prefer rise and other biologically productive areas. Although it was captured at a depth of 1570m, it generally lives above 1000m.

In Suruga Bay, it is most frequently seen at depths of 50–200m, except from August to November, when the temperature at 100m exceeds 15 ° C and sharks descend to deeper waters. On rare occasions, this species has been sighted on the surface.

The frilled shark is generally found near the bottom. However, its diet suggests that it makes significant forays to the surface.