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Facts about the Frilled Shark

Leena Palande
Ever wondered why the frilled shark has often been termed as a 'living fossil'? The reason behind it is that it exhibits several 'primitive' features. We bring you some intriguing facts about the frilled shark, a mysterious deep-sea species of sharks.

Did You Know?

The frilled shark, one of the world's strangest sea creatures, is thought to have changed little in about 80 million years. It bears a resemblance to ancestor species that lived during the time of the dinosaurs. It shows no signs of evolution since prehistoric times. So, it is often referred to as a 'living fossil'.
The frilled shark, one of the least seen sharks, is also known as a lizard shark, scaffold shark, or a silk shark. It is not commonly seen because it lives at depths of between several hundred and several thousand feet. It is an extant species of sharks and is usually found in the Atlantic and Pacific oceans.
It was thought to have long been extinct, however, it was discovered in the 19th century in Japanese waters.
The six pairs of gill slits that give it a fringed appearance have earned the species the descriptive name 'frilled shark'. The scientific name of the species is Chlamydoselachus anguineus. Its mouth is located at the terminal edge of its snout, and not underneath, like most other sharks.
As they are hardly seen, detailed information about how a frilled shark catches its prey, or how often it catches its prey is not available.

Interesting Facts about Frilled Sharks

The length of the shark can be about 2 m (6.6 ft). Females are larger than males. Males reach sexual maturity at 95 cm, females at 135 cm. The visible part or the upper body of the shark is dark brown or gray in color. The color of its belly is comparatively lighter.
The frilled shark size, its dark brown, elongated, eel-like body, broad and flattened head, short, rounded snout, expanding long jaws, an extremely wide gape, and several rows of needle-like, tricuspid teeth make it a scary-looking fish. These sharks or their giant relatives are thought to be a source for reports of sea serpents.
The frilled shark's diet consists of cephalopods (octopuses, squid, cuttlefish, etc.), bony fish, and smaller sharks. The fast-moving squid comprise about 60% of the diet of this shark. It can accommodate a large prey (over half its size) in its mouth. Most captured individuals showed no signs of stomach contents. This is an indication of a fast digestion rate and/or long intervals between feedings.
These sharks cannot swim fast. Due to the intense cold of its deep-sea habitat, its metabolic processes are slow and this makes it lethargic. Moreover, these sharks are not able to deliver a strong powerful bite force like their cousins.
However, their serpentine bodies help them catch fast-swimming slippery squid. It is believed that while preying, the shark bends its body and lungs forward like a snake. It is also believed that by closing the gill slits, it creates negative pressure and sucks the prey.
The numerous (300 teeth over 25 rows), needle-like, curved, pointed frilled shark teeth do not allow the prey to escape, once caught.
The anal fin is quite larger than the lobe-like dorsal fin. Apart from the small, paddle-shaped pectoral fins, they have very long caudal fins.
Frilled sharks typically have a pair of thick skin folds, running along their bellies, separated by a groove. The exact function of these folds is not known. It is believed that these folds accommodate the expansion of the digestive tract after the ingestion of a large prey.
Although some are caught at the depth of 1500 m, these sharks are believed to live at depths of 500-1000 m. They are rarely seen at the surface, but are sometimes found higher in the water column at depths between 50 and 200 meters. It is obvious that they feed on the species that are found in a similar habitat.
Research shows that the shark is perfectly adaptable for living in deep waters. It comes with a large, oil- and hydrocarbon-packed liver. The typical position of its fins and its large-sized liver having low-density lipids enable it to maintain its position in the water column with minimum effort. These features enable it to float and hover in deep waters.
The frilled shark is aplacental viviparous - the embryos emerge from the egg capsules when they are inside the mother's uterus. There, they are nourished by egg yolk. There is no placental connection between the young and the mother. The mother's body helps them exchange gases (oxygen and carbon dioxide). A female gives birth to 6 to 12 live young at a time, many of which may not survive into adulthood. The newly born pups are about 40 - 60 cm long.
There is no specific breeding season as such. The gestation period may be as long as three and a half years, the longest of any vertebrate (nearly twice as long as Asian elephants carry their young).
As these sharks are likely to mature late, and as they have a low reproductive rate, even incidental catches may eliminate the species over time.
The International Union for Conservation of Nature has assessed the species as 'Near Threatened'.
A terrifying frilled shark was recently (in Dec. 2014) caught in waters off south-eastern Australia. It was found as deep as 1,500 meters. Appearance of this rarely-sighted species was really horrifying. The one that was caught in Japan in 2007 died soon after it was put in a large seawater pool.
Frilled sharks pose little or no danger to human beings. Populations of the species seem to be more vulnerable to disease now, perhaps due to pollution and habitat changes (drastic changes in climate bring about a change in the temperature of seawater). It is very difficult to restore the frilled sharks' population, which is already on the decline.