The goblin shark (Mitsukurina owstoni) is a species of deep-sea shark found in aphotic zones worldwide. This pink-skinned animal has a distinctive profile with an elongated, flattened snout, and highly protrusible jaws containing prominent nail-like teeth. They live at depth up to at least 4265 feet (1300 m).
The goblin shark has a distinctively long and flat snout, resembling a sword blade. The proportional length of the snout decreases with age. The eyes are small and lack protective nictitating membranes, with spiracles behind the eyes. The large mouth is parabolic in shape with highly protrusible jaws and can be extended almost to the end of the snout, though normally they are held flush against the underside of the head. It has 35–53 upper and 31–62 lower tooth rows. The teeth in the main part of the jaws are long and narrow, particularly those near the jaw midpoint, and are finely grooved lengthwise. The teeth near the corners of the jaw are small and have a flattened shape for crushing. Much individual variation in tooth length and width occurs, in whether the teeth have a smaller cusplet on each side of the main cusp, and in the presence of toothless gaps at the symphysis or between the main and rear teeth. The five pairs of gill slits are short, with the gill filaments inside partly exposed. The fifth pair is above the origin of the pectoral fins.
Since it is not a fast swimmer, the goblin shark may be an ambush predator. Its low-density flesh and large oily liver make it neutrally buoyant, allowing it to drift towards its prey with minimal motions so as to avoid detection. Once prey comes into range, the shark’s specialized jaws can snap forward to capture it. The protrusion of the jaw is assisted by two pairs of elastic ligaments associated with the mandible joint, which are pulled taut when the jaws are in their normal retracted position. According to Wikipedia, when the shark bites, the ligaments release their tension and essentially “catapult” the jaws forward. At the same time, the well-developed basihyal (analogous to a tongue) on the floor of the mouth drops, expanding the oral cavity and sucking in water and prey. Striking and prey capture events were videotaped and recorded for the first time in 2008 and 2011 and helped to confirm the use and systematics of the protrusible goblin shark jaws.”
Although observations of living goblin sharks are scarce, its anatomy suggests its lifestyle is inactive and sluggish. Its skeleton is reduced and poorly calcified, the muscle blocks along its sides are weakly developed, and its fins are soft and small. Its long caudal fin, held at a low angle, is also typical of a slow-swimming shark. The long snout appears to have a sensory function, as it bears numerous ampullae of Lorenzini that can detect the weak electric fields produced by other animals. Due to the snout’s softness, it is unlikely to be used for stirring up prey from the bottom as has been proposed.
Given the depths at which it lives, the goblin shark poses no danger to humans. A few specimens have been collected alive and brought to public aquariums, though they only survived a short time. One was kept at Tokai University and lived for a week, while another was kept at Tokyo Sea Life Park and lived for two days. Its economic significance is minimal; the meat may be dried and salted, while the jaws fetch high prices from collectors. At one time, the Japanese also used it for liver oil and fertilizer.