Latin name

Chlamydoselachus anguineus

Other names

Lizard shark

Identification

The frilled shark is named for the wide skin folds formed by gill fibres covering the gill slits. There are 6 slits on each side. The membranes of the first pair join at the bottom to form a broad skin blade.

The body is very elongated. The head is broad and flattened, the muzzle short and rounded. The slit-shaped nostrils are arranged vertically and divided into inward and outward openings by skin folds. The large oval eyes are horizontally elongated. The nictitating membrane is absent. Along the abdomen there is a pair of skin folds separated by a furrow of unknown function. The midsection of the female is longer than that of the male and the pelvic fins are closer to the anal fin. The mouth of this shark is almost terminal, not deeper as in most other sharks. There are no furrows at the corners of the mouth. The denticles are small, but on the dorsal surface of the caudal fin they are large and sharp.

Teeth

The teeth are not closely spaced. There are 19-28 and 21-29 rows of teeth in the upper and lower jaws. There are about 300 teeth in the mouth. Each tooth has three curved tips of about the same length, with small cusps in between. 

Features of fish fins

The dorsal, anal and two pelvic fins are close together at the rear of the body. The pectoral fins are short and rounded. The pelvic and anal fins are large and rounded. The long caudal fin is almost triangular in shape and consists of a single upper lobe.

Fish colouring

The colour is a uniform dark brown or grey.

Distribution

Found in many areas of the Atlantic and Pacific Oceans across a wide range of latitudes. In the Atlantic, they are found from northern Europe to South Africa. In the eastern Atlantic, they are found off the northern coasts of Norway and Scotland, west of Ireland and from France to Morocco, including Madeira and Mauritania. In the central Atlantic, they are found along the Mid-Atlantic Ridge from north of the Azores to the Rio Grande Rise off the southern coast of Brazil, and along the Vavilov Ridge off the coast of West Africa. In the western Atlantic, these sharks are common in the waters off New England, Georgia and Suriname. In the western Pacific they are found from Honshu Island, Japan, to Taiwan and off the coasts of New South Wales, Tasmania and New Zealand. In the central and eastern Pacific, they have been observed in waters off Hawaii, California and northern Chile.

Habitat

Deep sea species. Found at depths of 120-1450 metres, although they rarely descend below 1000 metres. These bottom-dwelling sharks are sometimes found in the water column. At night they can make vertical migrations and rise to the surface in search of prey. This species shows spatial segregation based on size and reproductive readiness.

Size

The length of this shark can reach 2 metres, but is usually around 1.5 metres for females and 1.3 metres for males. The weight of an adult does not exceed 4 tonnes. The maximum known age is 25 years.

Behavior

Adapted to life at depth, their skeleton is poorly calcified and their liver is very large and rich in low-density lipids, allowing them to balance in the water column with minimal effort. It is one of the few shark species with an "open" lateral line: the hair cells that act as mechanoreceptors are located in depressions that are in direct contact with the surrounding seawater. This structure is considered basal in sharks and allows them to detect the smallest movements of potential prey. Many of the captured sharks were missing the tip of their tails, probably as a result of attacks by other shark relatives. 

Food and feeding habits

The long jaws of these sharks are highly elongated, allowing them to swallow whole prey up to half their own length. However, the length and structure of their jaws do not allow them to bite with the same force as sharks with a more traditional structure. Poorly identified food remains have been found in the stomachs of most sharks caught, indicating rapid digestion and long feeding intervals. The diet consists mainly of cephalopods, but also includes bony fish and other sharks. 

Reproduction

Reproduction by live birth without placenta. The developing embryo feeds mainly on egg yolk. Adult females have two functional oviducts and a functional uterus on the right side. Breeding is not seasonal as these sharks live at depths where seasonal changes are negligible.  There are between 2 and 15 pups per litter, with an average of 6. The female lays one egg in each oviduct every 2 weeks. Oogenesis and development of new eggs cease during pregnancy, probably due to lack of space in the body cavity.

Development

Eggs and embryos at an early stage of development are enclosed in a thin, ellipsoidal, golden-brown egg capsule. The 3 cm long embryo has a pointed head, fully developed jaws, external gills and all fins are present. The 6-8 cm long embryo sheds the egg capsule, which is removed from the mother's body. By this time the embryo has fully formed external gills. The size of the yolk sac remains almost unchanged until the embryo has grown to 40 centimetres. The sac then begins to shrink and disappears completely when the embryo reaches 50 centimetres in length. On average, the embryo grows 1.5 centimetres per month. Carrying the embryo lasts for a long time, possibly up to two years, and according to some data - at least 3.5 years, which puts these sharks at the top of the list for this parameter among all vertebrates. The size of newborn sharks is 40-60 cm. Males and females reach sexual maturity at lengths of 1-1.2m and 1.3-1.5m respectively.

Fishing

It has no commercial value due to its rarity and is sometimes caught as bycatch.

Relationship with a person

No danger to humans. Used for food.