Sunday, 16 January 2011

Goblin Shark: Prehistoric monster from the deep

Image showing a goblin shark (Mitsukurina owstoni)
Goblin Shark
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Lamniformes
Family: Mitsukurinidae
Genus: Mitsukurina
Species: Mitsukurina owstoni
Conservation Status: Least Concert (Not threatened)
Common Name(s): Goblin Shark, Elfin shark


The goblin shark is a hideous, strange-looking shark occurring in all three major oceans. First discovered in the waters of Japan more than a hundred years ago, it still remains a poorly understood species with many mysteries surrounding its existence.

It is the last surviving member of the family Mitsukurinidae, a lineage some 125 million years old. The species has been described as a "living fossil", thanks to its prehistoric appearance and its ancient lineage.

Distribution
Specimens have been caught in all three major oceans, indicating a global distribution of the species. In the Atlantic, Goblin sharks have been observed from the northern Gulf of Mexico, Suriname, French Guiana, and southern Brazil in the west, and France, Portugal, Madeira, and Senegal in the east. Individuals have also been sighted in seamounts along the Mid-Atlantic Ridge.

In the Indo-Pacific and Oceania, it has been recorded off South Africa, Mozambique, Japan, Taiwan, Australia, and New Zealand whereas a single specimen was collected off southern California. Juveniles occur frequently at the submarine canyons off southern Japan at depths of 100–350 m (~328–1,150 ft),

Specimens have been collected or sighted at depths of up 1,300 m (~4,265 ft). On rare occasions, individuals have been spotted in inshore waters as shallow as 40 m (~131 ft). In general, adults are found in greater depths than immature goblin sharks do.

Finally, it should be noted that the species distribution is uneven; the majority of known specimens come from the bays of Japan.


Distribution map for goblin shark (Mitsukurina owstoni )
Distribution map for  Goblin Shark


Description
Adults of this weird and fearsome looking shark species routinely grow to be 3-4 meters (10–13 ft) long and 160 kg (352 lbs) heavy. The biggest specimen ever caught was a female, with an estimated length of 5.4 to 6.2 m (18–20 ft) from the Gulf of Mexico, whereas the heaviest specimen was 210 kg (462 lbs) heavy and 3.8 m long. The limit of their size and weight remains a mystery.

The elongated, flattened, dagger-shaped snout is probably the most distinctive trait of the goblin shark. The snout is heavily pored on the underside. These pores are believed to be the external openings of the "ampullae of Lorenzini", special sensory organs, capable of detecting small electric fields produced by other animals. The proportional length of the snout decreases as they age. The snout is not hard or sharp enough to pin or kill prey.

It has very small eyes, five short gill-openings and a large, parabolic-shaped mouth. The mouth comes with protruding, nail-like frontal teeth and rear teeth that are accustomed for crushing. The eyes are black with bluish streaks in the iris and lack nictitating membranes; behind the eyes are spiracles. Their vision is presumed to be poor,  accounting the relatively small optic tectum in the shark's brain. Unlike most deep-sea sharks, the size of the pupils can change, indicating that sight may occasionally play an important role.

They have 35 to 53 upper and 31 to 62 lower tooth rows.

Similarly to most sharks, they have the typical semi-fusiform body which is soft and flabby. However, unlike most sharks, the fins aren't pointed but instead are low and rounded, with the anal and pelvic fins being larger than the dorsal.  The tail is heterocercal, with the upper lobe proportionately way longer to other shark species. The tail doesn't have a ventral lobe or precaudal pits.

The second most distinctive characteristic of the species is its pink coloration, the result of blood vessels located underneath the semi-transparent skin. Actually, it is the only known shark species colored this way. The fins' margins are translucent gray, or blueish.

Males reach sexual maturity at about 2.6 m (8.5 ft) long, while female maturation size is a mystery. There is no data on growth, aging, average and maximum lifespan.


Image showing a goblin shark (Mitsukurina owstoni) head with the jaws extended
 Goblin shark head with jaws extended


Behavior
The goblin shark is a bathydemersal deep-sea animal that prefers to stay just above the sea bottom. It usually stays at depths of  250 m (~820 ft), however, the deepest specimen ever caught was found at a depth of 1300 m (~4265ft). They can probably go even deeper, as a lodged tooth was once retrieved from an undersea cable, at a depth of 1.370 m (4,494 ft).

They usually inhabit the outer continental shelves and upper slopes and are found off seamounts. Very rarely, they will endeavor near  the surface or in shallow waters close to the sore.

Currently, there is almost no knowledge regarding other behavioral patterns, like reproduction as observations of living individuals are scant. Their anatomy suggests an inactive and sluggish lifestyle.

Since they are members of the Lamniformes order, it is assumed that they are ovoviviparous, meaning that the eggs hatch inside the mother's body, who then gives directly birth to young sharks. Mackerel sharks (as Lamniformes sharks are commonly known), are characterized by small litter sizes and embryos that grow during gestation, by eating the yolk of undeveloped eggs and  (a practise known as oophagy). The birth size is probably something close to 82 cm (~32.3 in) long, which is the length of the smallest specimen ever caught. A pregnant specimen has never been caught. Collecting and examining one would surely provide us with many answers.


Perhaps the only good quality footage showing a goblin shark.
This a young one, and the "biting" is staged.

Feeding & Diet
The goblin shark is not a good swimmer and is assumed to be an ambush predator. Its low-density flesh and large oily liver make it neutrally buoyant which helps it to drift towards prey with few motions, avoiding detection.

Similarly to other sharks, the goblin sharks sense their pray by using electro-sensitive organs in the rostrum. This electrosensory ability is exceptionally important to the goblin shark, due to the presence of very little light in the deep waters it inhabits and hunts.

The shark's jaws are highly specialized  and can instantly snap forward to catch prey. This jaw protrusion is assisted by two pairs of elastic ligaments, associated with the mandibular joint, which are pulled when the jaws are in their normal retracted position. When the goblin shark bites, the ligaments release their tension and essentially "catapult" the jaws forward. Furthermore, the shark has a well-developed basihyal (analogous to a tongue) that sucks the victim into the sharp frontal teeth.

Image showing the jaws of two different goblin shark specimens
In the past, differing jaw positions of preserved specimens led to several specimens erroneously
identified as different species

It primarily feeds on teleost fishes, like rattails and dragonfishes. It also consumes cephalopods and crustaceans, for instance decapods and isopods.  Its range of prey includes both bottom-dwelling species like the blackbelly rosefish (Helicolenus dactylopterus), and midwater species like the googly-eyed glass squid (Teuthowenia pellucida). This strongly suggests that the goblin shark hunts both near the sea floor and far above it.

A study on the stomachs of 148 specimens found teleost fishes, squids, decapods, isopods, digested food, and even human refuse! Surely, not a picky eater!

Image of a rattail which is common prey for goblin sharks
Rattails are common prey for goblin sharks

Natural Enemies
Goblin sharks perhaps may be hunted by the blue shark (Prionace glauca) and other large shark species, but there is no definite data on this. A study on a specimen collected off of Ulladulla, New South Wales, Australia and deposited at the Australian Museum in Sydney revealed that when alive, it was host to 4 different species of tapeworms, all recovered from the spiral intestine

Conservation Status
Although sightings of the the goblin shark are exceptionally rare, for the moment it is classified as of "least concern" by the IUCN. This, because the species has a wide distribution, with most populations believed to reside in areas with little to none fishing activities, as it is a very rare bycatch. Overall, the species doesn't seem to be immediately threatened by human related activities and their numbers seem to be stable.

The main human activities with some minor negative impact on the species are:
  • Fishing (although it is a rare practice)
  • Accidental fishing (bycatch)
  • Water Pollution 

Finally, there seems to be an interest for goblin shark jaws by collectors, with prices for jaws imported by Taiwan to the USA ranging from US$1,500?$4,000, depending on the quality, size and other factors.


Sightings and occurrences
Some worth-noting sightings are the following:
  • The first M. owstoni specimen was caught by a Japanese fisherman in the Kuroshio Current, off the coast of Yokohama, Japan in 1897. The specimen was later estimated to be a male, 3.5 ft long goblin shark. 
  • A goblin shark was discovered in waters off eastern Australia in 1985. In New Zealand, a specimen was caught three years later, in 1988.
  • A specimen was caught in waters off Tasmania in 2004 and was 4 meters long. The specimen was then taken to the national fish collection in Hobart.
  • During 2003, more than a hundred goblin sharks were caught off the northwest coast of Taiwan, an area in which they had never sighted before. These sharks were caught after a recent earthquake in the area
  • A goblin shark was held captive by the Tokai University,Japan, only to die a week later.
  • A 1.3 m long specimen was caught alive in Tokyo Bay, at a depth between 150 to 200 m (~500 - 650 ft) on January 25, 2007. It was transferred to the Tokyo Sea Life Park to be displayed, but died two days later.
  • In April 2007, a bunch of goblin sharks were reported swimming in shallow waters in the Japanese Sea and a live one was captured near the Tokyo Bay.
  • In August 2008, NHK filmed a live goblin shark in Japan. The shark was small, about 1.3 meters long.
  • Many specimens have been caught in the vicinity of New South Wales and Tasmania. These specimens are preserved at the Australian Museum.
  • In the Indian Ocean, a cable malfunction necessitated the raising of the cable. A nail-like tooth was found embedded in the wire covering. The tooth was later reported to belong  to a goblin shark.
  •  In April 2014, a shrimper in Key West, Florida, while fishing in the Gulf of Mexico, pulled out a goblin shark in a fishing net that was 600 m (~2000 feet) deep down. This is only the second goblin shark to have been caught in the Gulf of Mexico.

In captivity
The species doesn't do well in activity and dies shortly after. As aforementioned, the specimen in the Tokai University died a week later whereas the one at Tokyo Sea Life Park just two days later.


Are they dangerous?
Due to the predominantly deep oceanic levels they occupy, goblin shark pose little -if any- danger to humans. There have been no recorded attacks and therefore injuries to humans.

Comparison between an average human and a goblin shark
Comparison between an average adult goblin shark and a diver


Discovery
The species was first described in 1898, by American ichthyologist David Starr Jordan (1851-1931), using an immature male as a basis. The specimen was 107 cm (~42 in) long. Jordan recognized the weird fish not only as a new species, but also as a new genus and family.

The young specimen was caught in Sagami Bay near Yokohama and had been acquired by shipmaster and amateur naturalist Alan Owston (1853–1915), who then gave it to Professor Kakichi Mitsukuri at the University of Tokyo. Mitsukuri then gave it to Jordan.  

Jordan named the newly discovered shark in honor of these two men.

Interesting Facts about Goblin sharks
After death, the pink coloration quickly fades and becomes a dull gray or brown.
- Females seem to be slightly larger than males.
Goblin shark is a translation of its old Japanese name "tenguzame". Tengu are a type of legendary creature found in Japanese folk religion, often depicted with a long nose and red face.

Image showing a tengu, from which goblin sharks are named after
A tengu shrine


References
Parsons, G., Ingram, G., & Havard, R. (2002). FIRST RECORD OF THE GOBLIN SHARK MITSUKURINA OWSTONI, JORDAN (FAMILY MITSUKURINIDAE) IN THE GULF OF MEXICO Southeastern Naturalist, 1 (2), 189-192 DOI: 10.1656/1528-7092(2002)001[0189:FROTGS]2.0.CO;2
- Duffy, C. (1997). Further records of the goblin shark, (Lamniformes: Mitsukurinidae), from New Zealand New Zealand Journal of Zoology, 24 (2), 167-171 DOI: 10.1080/03014223.1997.9518111
- Rincon, G., Vaske, T., & Gadig, O. (2012). Record of the goblin shark Mitsukurina owstoni (Chondrichthyes: Lamniformes: Mitsukurinidae) from the south-western Atlantic Marine Biodiversity Records, 5 DOI: 10.1017/S1755267211000923
- Yano, K., Miya, M., Aizawa, M., & Noichi, T. (2007). Some aspects of the biology of the goblin shark, Mitsukurina owstoni, collected from the Tokyo Submarine Canyon and adjacent waters, Japan Ichthyological Research, 54 (4), 388-398 DOI: 10.1007/s10228-007-0414-2
- Masai H, Sato Y, & Aoki M (1973). The brain of Mitsukurina owstoni. Journal fur Hirnforschung, 14 (6), 493-500 PMID: 4792175
- Caira, J., & Runkle, L. (1993). Two new tapeworms from the goblin shark Mitsukurina owstoni off Australia Systematic Parasitology, 26 (2), 81-90 DOI: 10.1007/BF00009215
- Jordan, D.S. (1898). "Description of a species of fish (Mitsukurina owstoni) from Japan, the type of a distinct family of lamnoid sharks". Proceedings of the California Academy of Sciences (Series 3) Zoology 1 (6): 199–204.
- Some aspects of the biology of the goblin shark, Mitsukurina owstoni, collected from the Tokyo Submarine Canyon and adjacent waters, Japan
-  Compagno, L.J.V. (2002). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date (Volume 2). Food and Agriculture Organization of the United Nations. pp. 68–71. ISBN 92-5-104543-7.

3 comments:

  1. Wow that shark looks scary

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    Replies
    1. I don't think this shark looks scary at all . I think this shark is just very weird looking.

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