The frilled shark from the Chlamydoselachidae family takes pride of place in the ranking of the most unique fish. This dangerous creature is considered the king of the depths of the underwater world. Originating from the Cretaceous period, this frilled predator has not changed over a long time of existence, and practically did not evolve. Due to anatomy and morphology, the two surviving species are considered to be the most ancient sharks in existence. For this reason, they are also called “living fossils or relics”. The generic name consists of the Greek words χλαμύς/chlamys “coat or cloak” and σέλαχος/selachos “cartilaginous fish”.
View origin and description
For the first time, the cloaked shark was described from a scientific point of view by the German ichthyologist L. Doderlein, who visited Japan from 1879 to 1881 and delivered two specimens of the species to Vienna. But his manuscript describing the species has been lost. The first description that has come down to us was documented by the American zoologist S. Garman, who discovered a 1.5 m long female caught in Sagami Bay. His report The Extraordinary Shark was published in 1884. Garman placed the new species in his genus and family and named it Chlamydoselachus anguineus.
Fun Fact: Some early researchers believed that the frilled shark was a living member of an extinct group of elasmobranch cartilaginous fish, but more recent studies have shown that similarities between the frilled shark and extinct groups are overstated or misinterpreted, and this shark has a number of skeletal and muscular traits that strongly associated with modern sharks and rays.
Fossils of frilled sharks on the Chatham Islands in New Zealand, dated to the Cretaceous-Paleogene boundary, were found along with the remains of birds and conifers, indicating that these sharks lived in shallow water at that time. Previous studies of other Chlamydoselachus species have shown that individuals living in shallower water had large, strong teeth for eating hard-shelled invertebrates.
Video: Frilled Shark
In this regard, it has been suggested that frilled birds survived the mass extinction, were able to use free niches in shallow water and on continental shelves, the latter opening up movement to the deep-sea habitats in which they now live.
The change in food availability may be reflected in how the morphology of the teeth changed, becoming sharper and inward directed to prey on soft-bodied deep-sea animals. From the late Paleocene to the present day, frilled sharks have been unrivaled in their deep-sea habitats and distribution.
Appearance and Features
Frilled eel sharks have a long, slender body with an elongated tail fin, giving them an eel-like appearance. The body is uniform chocolate brown or gray in color, with prominent wrinkles on the belly. There is a small dorsal fin located closer to the tail, above the large anal fin and in front of the highly asymmetrical caudal fin. The pectoral fins are short and rounded. Frilled sharks are part of the Hexanchiformes order, which is considered the most primitive group of sharks.
Within the genus, only the last two species are distinguished:
- frilled shark (C. anguineus);
- South African frilled shark (C. africana).
The head has six gill openings (most sharks have five). The lower ends of the first gill extend over the entire throat, while all other gills are surrounded by frilly skin edges — hence the name “frilled shark”. The muzzle is very short, and looks like a cut off, the mouth is greatly expanded and finally attached to the head. The lower jaw is long.
Interesting fact: The frilled shark C. anguineus differs from the South African relative C. africana in that it has more vertebrae (165–171 versus 146) and more coils in spiral valve gut, as well as various proportional measurements, such as a longer head and shorter slits on the gills.
The teeth on the upper and lower jaws are uniform, with three strong and sharp crowns and a pair of intermediate crowns. The anal fin is larger than the single dorsal fin, and the caudal fin lacks a subterminal groove. The maximum known length of the frilled shark is 1.7 m for males and 2.0 m for females. Males become sexually mature when they are barely a meter long.
Where does the frilled shark live?
The rather rare shark is found in a number of widely scattered locations in the Atlantic and Pacific Oceans. In the eastern Atlantic, it lives off northern Norway, northern Scotland and western Ireland, along France to Morocco, with Mauritania and Madeira. In the mid-Atlantic, the shark has been caught in several locations along the Mid-Atlantic Ridge, from the Azores to the Rise of the Rio Grande off southern Brazil, and off the Vavilov Ridge off West Africa.
In the west of the Atlantic, she was seen in the waters of New England, Suriname and Georgia. In the western Pacific Ocean, the range of the frilled shark covers the entire southeast around New Zealand. In the center and east of the Pacific Ocean, it is found in Hawaii and California in the USA and in northern Chile. The frilled shark, found off southern Africa, was described as a distinct species in 2009. This shark is found on the outer continental shelf and on the upper and middle continental slopes. It is found at a depth of even 1570 m, although it is usually not found deeper than 1000 m from the ocean surface.
In Suruga Bay, the shark is most common at a depth of 50–250 m, except from August to November, when the temperature of the 100 m water layer exceeds 16 ° C and the sharks move into deeper waters. On rare occasions, this species has been sighted on the surface. The frilled shark is usually found close to the bottom, in areas of small sand dunes.
However, its diet suggests that it makes significant forays up into open water. This species can make vertical ascents, approaching the surface at night to feed. There is spatial segregation in size and reproductive status.
Now you know where the frilled shark is found. Let's see what this cloaked man eats.
What does the frilled shark eat?
The elongated jaws of the frilled shark are very mobile, their holes can stretch to extraordinary sizes, allowing them to swallow any prey that does not exceed half the size of the individual. However, the length and structure of the jaws shows that the shark cannot make a strong bite like the common shark species. Most of the fish caught have no or barely identifiable stomach contents, indicating an extremely high rate of digestion or long breaks between feedings.
Frilled sharks prey on cephalopods, bony fish and small sharks. In one 1.6 m long specimen caught, 590 g of Japanese cat shark (Apristurus japonicus) were found. Squid make up about 60% of the shark diet in Suruga Bay, which includes not only slow-moving deep-sea squid species such as Histioteuthis and Chiroteuthis, but rather large, powerful swimmers such as Onychoteuthis, Todarodes and Sthenoteuthis.
The frilled shark feeds on:
The method of catching actively moving squid by the slow-swimming frilled shark is the subject of speculation. Perhaps it captures already injured individuals or those who are exhausted and will die after spawning. In addition, she can capture the victim by bending her body like a snake and, leaning on the ribs located behind, deliver a quick blow forward.
It can also close slits in its gills, creating negative pressure to suck in prey. A frilled shark's many small, curved teeth can easily hook on a squid's body or tentacles. They can also eat carrion that descends from the surface of the ocean.
Character and lifestyle features
The Frilled Shark — a slow deep-sea shark adapted to life on the sandy bottom. This is one of the slowest shark species, highly specialized for life deep in the sea. It has a reduced, poorly calcified skeleton and a huge liver filled with low-density lipids, which allows it to maintain its position in the water column without much effort.
Its internal structure can increase sensitivity to the smallest movements of prey. Many individuals are found without the tips of their tails, probably as a result of attacks by other species of sharks. The frilled shark can capture prey by bending its body and lunging forward like a snake. Long, rather flexible jaws allow it to swallow prey whole. This species is viviparous: embryos appear from egg capsules inside the mother's uterus.
These deep-sea sharks are also sensitive to sounds or vibrations from a distance and to electrical impulses emitted from the muscles of the animals. In addition, they have the ability to detect changes in water pressure. There is little information on the lifespan of the species, probably the maximum level is in the range of 25 years.
Social Structure and Reproduction
Fertilization occurs internally, in the female's egg tubes or oviducts. The male sharks must grab the female, maneuver her body to insert their clamps and direct the sperm into the hole. Developing fetuses are fed primarily from the yolk, but the difference in weight between the newborn and the egg indicates that the mother provides additional nutrition from unknown sources.
Adult females have two functional ovaries and one uterus on the right. The species does not have a specific breeding season, since the frilled shark lives in depths where there is no seasonal influence. Possible mating population of 15 male and 19 female sharks. Litter size ranges from two to fifteen cubs, with an average of six. The growth of new eggs is stopped during pregnancy, possibly due to lack of space inside the body cavity.
Newly ovulated eggs and embryos at an early stage of development are enclosed in a thin ellipsoid golden brown capsule. When the embryo is 3 cm long, its head becomes pointed, the jaws are almost not developed, external gills begin to appear and all fins are already visible. The egg capsule is shed when the embryo reaches 6–8 cm in length and is removed from the body of the female. At this time, the external gills of the embryo are fully developed.
The size of the yolk sac remains constant until about an embryonic length of 40 cm, after which it begins to decrease, mostly or completely disappearing at an embryonic length of 50 cm. The embryonic growth rate averages 1.4 cm per month, and the entire gestation period lasts three and a half years, much longer than other vertebrates. Sharks born are 40–60 cm long. Parents don't take care of their babies at all after birth.
Natural enemies of frilled sharks
Yes several known predators that prey on these sharks. Apart from humans, who kill most of the sharks caught in nets as bycatch, small sharks are regularly preyed upon by mostly large fish, rays and larger sharks.
Near the coast, small frilled sharks that rise closer to the surface of the water are also caught by seabirds or seals. Because they occupy the benthos, they are sometimes caught while bottom trawling or in nets when they venture closer to the surface. Great frilled sharks can only be caught by killer whales and other large sharks.
Interesting fact: The frillers are bottom dwellers and can help remove decaying carcasses. Carrion descends from the open waters of the ocean and stops at the bottom, where sharks and other benthic species play an important role in the processing of nutrients.
These are not dangerous sharks, but their teeth can tear the hands of an unwary explorer or fisherman holding them. This shark is regularly caught in Suruga Bay in bottom gillnets, as well as in full-water shrimp trawls. Japanese fishermen regard this as a nuisance as it damages the nets. Due to the low reproductive rate and the continued advance of commercial fishing into its habitat, there are fears of its existence.
Population and species status
The frilled shark has a wide but very heterogeneous distribution in the Atlantic and Pacific Oceans. There is no reliable information about the number of populations and trends in the development of the species at the current stage. Little is known about its life history, this species is likely to have very low tolerance to changing external pressures. This deep-sea shark is rarely seen as bycatch in bottom trawling, medium underwater trawling, deep sea longline fisheries and deep sea gillnet fisheries.
Interesting fact: The commercial value of frilled sharks is small. They are sometimes mistaken for sea snakes. As by-catch, this species is rarely used for meat, more often for fishmeal or discarded altogether.
Deep sea fisheries have expanded over the past few decades and there is some concern that continued expansion, both geographically and in depth of capture, will increase by-catch levels of the species. However, based on its wide range and the fact that many of the countries where the species has been caught have effective fishing restrictions and depth limits (e.g. Australia, New Zealand and Europe), this species is rated as Least Concern.
However, its apparent rarity and inherent sensitivity to overexploitation means that catches in the fishery must be closely monitored, through fishery-specific data collection and monitoring, to ensure that the species is not threatened in the near future.
Fried Shark Conservation
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The frilled shark is classified as critically endangered on the IUCN Red List. There are national and regional initiatives to reduce by-catch of deep-sea sharks that are already beginning to pay off.
In the European Union, based on recommendations from the International Council for the Exploration of the Sea (ICES) to stop fishing for deep-sea sharks, the European Union (EU) Fisheries Council has set a zero limit on the total allowable catch for most sharks. In 2012, the EU Fisheries Council added frilled sharks to this measure and set a TAC level of zero for these deep sea sharks.
Fun fact: Over the past half century, deep sea fisheries have increased to depths of up to 62, 5 m per decade. There is some concern that if deep sea fisheries continue to expand, the by-catch of these species could also increase. However, in many countries where the species is found, there are effective management and depth restrictions for fishing.
The frilled shark is occasionally kept in aquariums in Japan. In the Australian Southern and Eastern Fish and Salt Shark Commonwealth trawl sector, most areas below 700 m are closed to trawling, providing a haven for this species. If deeper waters are to be reopened to fisheries, by-catch levels for this and other deep-sea sharks should be monitored. Catch and species specific monitoring data will help you understand how bycatch affects fish populations.