Genus- Species-Authority-Date
Goblin sharks were first given a genus when they did not match into any genera of the living or fossil record of lamniform. Zoologist David Starr Jordan identified the shark and gave it a genus named after Professor Kakichi Mitsukuri, the professor from Japan whom the shark was brought over by from the university of Tokyo, Japan (Jordan 1898). Jordan by the request of Professor Mitsukuri made the species name after Mr. Allen Owston, the man who gave him the specimen and the genus after himself thus dubbing the mystery shark: Mitsukurina owstonii (Jordan 1898). The common name for M. owstonii (Jordan 1898) , goblin shark, came from the Japanese creature after which it was named Tengu, or a spirit with a large protruding nose, that was almost bird-like in nature, which was mistranslated to be the Japanese equivalent of a goblin (Martin 1999).
Systematics and relationships
Chondrichthyes is the class to which all cartilaginous fish belong. Elasmobranchii is the class including families of sharks and rays. Lamniform is the order of sharks which include the Great White, Salmon shark, Mako shark, and goblin sharks. These are referred to as Mackerel sharks due to the trend that their caudal peduncles similar to the mackerels on which they feed. Lamnoidei describes the members of the laminformes’ order; a total of 15 living members (Compagno 2008). Mitsukurinae is the name given to goblin sharks’ family. There are six members of which five are extinct relatives of the goblin shark and one currently described living species M. owstonii (Jordan 1898).
Description and key characters
The goblin shark reaches between 3.1 m to 6.2 m long, from the tip of the rostrum to the end of the caudal fin. The goblin shark has a pink to a light cream white color since it inhabits the abyssal waters beyond the reach of sunlight. This eliminates the need for pigmentation to hide from predators and from unsuspecting prey(Yano 2007). The Goblin shark has a flabby and robust trunk comparatively to other deep-sea sharks(Yano 2007). Unlike most sharks, Goblin sharks lack a nictitating membrane around the eyes, which is a trait of their order the Lamnoids. Goblin sharks are heterodonts, having cuspidate and slender, erect, lanceolate-type teeth (Yano 2007). Yano performed teeth counts and noticed the teeth lack a basal cusp, another difference between Goblin Sharks and their cousins in the Lamnoid order. Goblin sharks have two dorsal fins which are typical of other sharks in the Lamnoid order. The goblin shark’s snout is broad which allows for easy identification as it is one of the namesake features the “Tengu” (Yano 2007). the goblin shark is missing a defined lower lobe on its caudal fin which makes it distinct from those in the Lamnoid order like Carcharodon Carcharias (Smith 1838) for example. The Great White Shark has a very distinct lower caudal lobe to help propel itself through the water (Camhi 2008). The fact that the goblin shark retains ancestral traits and has few derived traits may be due to goblin sharks being the basal specimen of the lamniformes (Martin 1999).
Distribution and abundance.
The goblin shark was originally thought to only inhabit the submarine canyons off the coast of Japan, though it has since been caught off the Gulf of Mexico, Brazil, Australia, Taiwan, and New Zealand (Rincon, Vaske, Gadig 2012). The Goblin Shark’s deep-water habitat makes it a challenge to determine the exact extent of its habitation. These independent sightings, however, allowed scientists to estimate a range of almost every ocean except for the Arctic and Antarctic, as far as current reports can tell. The depths of nearly 700 m to 1300 m provide plenty of dark places for the goblin sharks to hide without a trace (Rincon 2012).The goblin shark has been found in many locations around the globe but there are no thoughts currently as of yet about abundance but it might be assumed that they are more populous around japan as that is where they have been caught in the most numbers. These traits would suggest that Goblin sharks are most likely lone animals with a wide range, following the submarine canyons and cliffs while being one of the deep-sea apex predators. The goblin sharks that have been caught for study have been caught off of continental shelves, slopes, seamounts, and off the coast in deep waters (Orlov, Afanasiev, Pelenev, 2017). These are some of the reasons the goblin shark is believed to be a mesopelagic fish as opposed to its pelagic cousins.
Ecology and life history
Goblin sharks have been caught at depths ranging from 100m to 1300 m but they most often habituate the region between 100m and 960m (Orlov 2017). These pathways seem to follow a trend of being near seamounts, continental slopes, and ridges. The goblin shark maintains a balance in seawater by keeping lipids stored in the liver at high concentrations, allowing it to be nearly neutrally buoyant in the water column (Duffy 1997). The goblin shark uses multiple kinds of teeth to try and capture benthic prey items like ratfishes, isopods, and squid (Duffy 1997). The Goblin shark relies on its elongated rostrum to detect prey and navigate the inky blackness of the deep sea. The rostrum is lined with ampullae of lorenzini, which are thought to act as a transceiver of electric signals from moving prey as the goblin shark sits motionless in the water column (Yano 2007). The goblin shark is thought to be a slow swimmer as it has the asymmetrical caudal fin which does not allow for maintained fast speeds but possibly allows for short bursts, which lends itself to be a mesopelagic, motionless stalker (IUCN 2007). The goblin shark can grow up to 6.2 m, but until it grows to a juvenile size, the shark is susceptible to predation by larger fish and other organisms. There is no evidence of goblin sharks interacting symbiotically with any other organisms. Though goblin sharks may use seamounts and coastlines to navigate on their massive migratory paths they might also use their lateral lines to navigate from place to place via the earth’s magnetic field. There is little known about the life history of the goblin shark, though adults of both sexes have been caught and studied. There has yet to be a pregnant specimen which would allow a closer examination of the larval stages.
Reproduction.
The Goblin shark is thought to have similar reproductive strategies to other lamnoid sharks involving oviviparous birth with oophagous strategies (Gilmore 1993). This is common in Sand Tigers, Great Whites, and other Lamniformes. The young who develop early most likely consume the smaller littermates as well as undeveloped eggs as this can be seen with Sand tiger sharks Carcharias taurus Rafinesque,1810. The strategy of producing young viviparously allows for a few young to be well developed and ready to emerge provides a better chance rather than egg laying which is low-energy and high-yield with less success. The goblin shark has not been caught while pregnant so there is no definitive answer on the size and number of their litters. Juveniles have been caught, which allow comparisons between them and adults, though the only differences seem to be that the claspers were uncalcified in the males and the female’s ovaries were not fully in use (Gilmore 1993). There has not been, to date, an attempt to study the age of the goblin shark and no past studies have included information about the size of crystals deposited inside the shark as a way of checking the age.
Behaviors
Goblin sharks are thought to be mainly slow and sluggish animals which prefer to hang in the water columns and predate while other fish are moving. In order to achieve such a distinct and specialized feeding behavior, they would need a weapon to match their own unusual look. The goblins shark has pioneered a unique ability to slingshot feed, in which it allows its upper jaw to extend out while the lower jaw engulfs the prey item (Nakaya 2016). This is one of the fastest feeding motions in the ocean. In a wild study of goblin sharks at depth by the Japanese Broadcast Association, the feeding is clocked in at 1.379 seconds to engulf a fish (Nakaya 2016). The goblin sharks can retract, set, and fire their jaws in a large gape before prey can react to the pressure wave of the mouth movement. The shark’s jaws can extend 1 to 9 times as far from its head, thanks to the “slingshot” effect of its feeding, which surpasses its fellow lamniformes (Nakaya 2016). This hunting behavior is evolutionarily beneficial to hunt prey undergoing vertical migrations and to overcome being a slow swimmer. Vertical migrations usually take place when animals in the aphotic zones of the ocean move upwards in the water column towards the surface. Organisms that the Goblin shark feeds on, like teleost and squid, will often make this journey to breed or feed at the surface. This allows the goblin shark to patrol and prey on them with nearly instantaneous precision. The goblin shark’s reproductive behaviors, like most sharks, remain a mystery hidden in the depths, as there are no ideas for a specific location for breeding or footage of multiple goblin sharks congregating, except for one instance after a typhoon(Gilmore 1993).
Conclusion
The goblin shark is one of the most unique morphological examples of a shark today, especially with its lineages connecting to one of the most respected shark families: the Lamniformes, which have been brought into the public eye in both good and bad light. The goblin shark has awed people ever since they were caught by Japanese fisherman and were seen as a sign of bad luck. The goblin shark’s awe-imposing look has led it to be very popular in the media, appearing in the star-studded “Shark Week” 2017 on “Alien Sharks”. These majestic creatures of the deep, seemingly undisturbed by time, are referred to as living fossils. This allows for us to study an animal which has preserved a lineage from the Holocene, as well as examine the possible connections to extinct species of lamniformes and put together a more proper, cladistical study. The goblin shark might just be the flagship species for other species of shark unknown to man beneath the inky blackness of abyssal trenches. The goblin shark also provides a reason to support the efforts of deep sea exploration , of which much is still unknown, but with every dive scientists learn more. The goblin shark is one of the most interesting sharks to have ever inhabited the seas with its unique extended rostrum, asymmetrical caudal fin, and slingshot feeding. Before further study and appreciation, the goblin shark will continue to swim the seas in the same way it has for the past 12,000 years and its extinct cousins did millions of years ago.
