The Frilled shark (Chlamydoselachus anguineus) is a species of shark in the family Chlamydoselachidae, that can be found in the Atlantic and Pacific Oceans over the outer continental shelf and upper continental slope, generally near the bottom. Current research suggests that they do undergo upward movement. They have been found as deep as 5,150 feet but are uncommon below 3,900 feet. In Suruga Bay, Japan, it is most common at depths of 160–660 feet.
Many refer to the Frilled shark as a living fossil. It reaches a length of 6.6 feet and has a dark brown, eel-like body with the dorsal, pelvic, and anal fins placed far back. Its common name comes from the frilly or fringed appearance of its six pairs of gill slits starting at the throat.
Family: Chlamydoselachidae – Frilled sharks
Common Name– Cow and Frilled Sharks
Common Name– Frilled Sharks
Status: IUCN Red List LEAST CONCERN
Average Size and Length: The maximum length of a female Frilled shark is 6.6 feet, and 5.6 feet for males.
Current Rare Mythical Sightings: The Frilled shark belongs to one of the oldest still-extant shark lineages, dating back to at least the Late Cretaceous (about 95 Mya) and possibly to the Late Jurassic (150 Mya). Due to their ancient ancestry and primitive characteristics, the Frilled shark and other members of this line have been described as a living fossil. However, the Frilled shark itself is a recent species, with the earliest known fossil teeth belonging to this species dating to the early Pleistocene era. Because of its unique appearance, it has long been thought of as a mythical sea serpent.
Fossils of frilled sharks from the Takatika Grit of the Chatham Islands in New Zealand, dated to the Cretaceous–Paleogene boundary, were found together with those of birds and conifer cones, which suggests that the sharks lived in shallow waters at that time. Previous research on other Chlamydoselachus species has shown that individuals living in shallower water had larger and stronger teeth for eating hard-shelled invertebrates. It has been hypothesized that frilled sharks, surviving the mass extinction of the K-T boundary event, were able to make use of vacated niches in shallow water and on continental shelves, the latter opening up a move to the deep-water habitats they now inhabit. Changing food availability may be reflected in how tooth morphology has shifted to become sharper and inward-pointing to prey on soft-bodied deep-sea animals. From the Late Paleocene to the present, frilled sharks may have been out-competed, restricting them to their current habitats and distribution. (Consoli, Christopher, P. (2008). “A rare Danian (Paleocene) Chlamydoselachus (Chondricthyes: Elasmobranchii) from the Takatika Grit, Chatham Islands, New Zealand”. Journal of Vertebrate Paleontology. 28 (2): 285–290.)
Teeth and Jaw: The Frilled shark has very long jaws that are positioned terminally, as opposed to the underslung jaws of most sharks. The corners of the mouth are devoid of furrows or folds. The tooth rows are widely spaced, numbering 19–28 in the upper jaw and 21–29 in the lower jaw. The teeth number around 300 in all; each tooth is small, with 3 slender, needle-like cusps alternating with 2 cusplets.
The long jaws of the Frilled shark are highly distensible with an extremely wide gape, allowing it to swallow prey whole over one-half its size. The length and articulation of its jaws means that it cannot deliver as strong a bite.
Head: The head of the Frilled shark is broad and flattened with a short, rounded snout. The nostrils are vertical slits, separated into incurrent and excurrent openings by a leading flap of skin. The moderately large eyes are horizontally oval and lack nictitating membranes.
Tail: The caudal fin is very long and roughly triangular, without a lower lobe or a ventral notch on the upper lobe.
Demographic, Distribution, Habitat, Environment and Range: The Frilled shark has been found in wide, patchy, scattered locations in the Atlantic and Pacific Oceans. In the eastern Atlantic, it can be found off northern Norway, northern Scotland, and western Ireland, from France to Morocco including Madeira, and off Mauritania. In the central Atlantic, it has been caught at several locations along the Mid-Atlantic Ridge, from north of the Azores to the Rio Grande Rise off southern Brazil, as well as over the Vavilov Ridge off West Africa. In the western Atlantic, it has been reported from waters off New England, Georgia, and Suriname. In the western Pacific, it is known from southeastern Honshu, Japan, to Taiwan, off New South Wales and Tasmania in Australia, and around New Zealand. In the central and eastern Pacific, it has been found off Hawaii and California in the US, and northern Chile.
The Frilled shark is benthic, epibenthic and pelagic. It prefers the outer continental shelf and upper to middle continental slope with lots of life. The Frilled shark has been caught at a depth of 5,150 feet, however it usually doesn’t venture deeper than 3,900 feet. In Suruga Bay, it is most common at a depth of 160–660 feet, except from August to November when the temperature at the 330 feet water layer exceeds 59 °F. When this happens, they transition into deeper water. The Frilled shark is usually found close to the bottom, with one individual observed swimming over an area of small sand dunes. On occasion they have been found at the surface. The diet of the Frilled shark suggests that they preform a diel vertical migration in open water towards the surface. There is spatial segregation by size and reproductive condition.
Diet: The Frilled shark preys on cephalopods, bony fishes, and smaller sharks. Squid comprise some 60% of the diet of sharks in Suruga Bay, both slow- and fast-moving squid species. Possibly picking off tired and injured ones. The many small, sharp, recurved teeth of the frilled shark are functionally similar to squid jigs and could easily snag the body or tentacles of a squid, particularly as they are rotated outwards when the jaws are protruded. Observations of captive frilled sharks swimming with their mouths open suggest that the small teeth, light against the dark mouth, may even fool squid into attacking and entangling themselves. (Ebert, D.A.; Compagno, L.J.V. (2009). “Chlamydoselachus africana, a new species of frilled shark from southern Africa (Chondrichthyes, Hexanchiformes, Chlamydoselachidae)“.
Many frilled sharks are found with the tips of their tails missing, probably from predatory attacks by other shark species.
Aesthetic Identification: The Frilled shark is uniform dark chocolate brown, grey, or blackish and has an elongated eel-like body. There are 6 pairs of long gill slits with a frilly appearance created by the extended tips of the gill filaments, giving this shark its name. The first pair of gill slits meet across the throat, forming what appears to be a collar. The pectoral fins are short and rounded. The single, small dorsal fin is positioned far back on the body, about opposite the anal fin, and has a rounded margin. The pelvic and anal fins are large, broad, and rounded, and also positioned well back on the body. There are a pair of thick skin folds of unknown function running along the belly, separated by a groove. The midsection is relatively longer in females than in males, with the pelvic fins pushed closer to the anal fin.
Biology and Reproduction: The Frilled shark differs from the Southern African Frilled shark, having more vertebrae (160–171 vs 147) and more turns in the spiral valve intestine (35–49 versus 26–28), as well as in various proportional measurements such as a longer head and shorter gill slits.
The Frilled shark is specialized for deep sea life. It has a poorly calcified skeleton and a large liver filled with low-density lipids, allowing it to maintain its position in the water column with little effort.
Parasites recognized on the Frilled shark include a tapeworm in the genus Monorygma, the fluke Otodistomum veliporum, and the nematode Mooleptus rabuka.
Most captured individuals are found with no or barely identifiable stomach contents, suggesting a fast digestion rate and/or long intervals between feedings.
The Frilled shark is ovoviviparous. A possible mating aggregation of 15 male and 19 female sharks has been recorded over a seamount on the Mid-Atlantic Ridge. The litter size ranges from 2 to 15 pups, with an average of 6 pups.
Adult females have two functional ovaries and one functional uterus, on the right. Females ovulate eggs into the uterus about once every two weeks; vitellogenesis (yolk formation) and the growth of new ovarian eggs halt during pregnancy, apparently due to insufficient space inside the body cavity. Newly ovulated eggs and early-stage embryos are enclosed in a thin, ellipsoid, golden-brown capsule. When the embryo is 1.2 inches long, the head is pointed when seen from above or below, the jaws are barely developed, the external gills have begun to appear, and all the fins are present. The egg capsule is shed when the embryo grows to 2.4–3.1 inches long and is expelled from the female’s body; at this time the embryo’s external gills are fully developed. The size of the yolk sac remains mostly constant until around an embryonic length of 16 inches, at which point it begins to shrink, mostly or completely disappearing by an embryonic length of 20 inches. The embryonic growth rate averages 1.4 cm per month, and therefore the entire gestation period may last three and a half years, far longer than any other vertebrate. (Tanaka, S.; Shiobara, Y.; Hioki, S.; Abe, H.; Nishi, G.; Yano, K. & Suzuki, K. (1990). “The reproductive biology of the frilled shark, Chlamydoselachus anguineus, from Suruga Bay, Japan”. Japanese Journal of Ichthyology. 37 (3): 273–291.)
Newborn sharks measure 16–24 inches long; males attain sexual maturity at 3.3–3.9 feet long, and females at 4.3–4.9 feet long.
Behavioral Traits, Sensing and Intelligence: The Frilled shark is one of the few sharks with an open lateral line, in which the mechanoreceptive hair cells are positioned in grooves that are directly exposed to the surrounding seawater. This is thought to enhance its sensitivity to the miniscule movements of its prey.
Speed: The Frilled shark is a slow-moving shark. Some scientists believe it could possibly launch brief, quick strikes forward.
Frilled shark Future and Conservation: Small numbers of frilled sharks are caught incidentally by various deep-water commercial fisheries around the world, using trawls, gillnets, and longlines. The Filled shark damages nets, and therefore fisherman just see it as an annoyance.
The Frilled shark is sometimes sold for meat or processed into fishmeal but is not economically significant. It was listed as Near Threatened in the past due to low reproduction and expanding commercial fishing however it has been downgraded to least concern.
Frilled shark Recorded Attacks on Humans: Harmless to humans. There have been rare cases of Frilled sharks caught at the surface that die soon after possibly from weakness from warm water, injury or illness. Scientists have accidently cut themselves on their teeth.