Bathykorus bouilloni
Encyclopedia
Bathykorus bouilloni is a species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

 that was first described in 2010. It is a deep sea species found in the Arctic Ocean
Arctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...

 and seems to be common below about 1000 m (3,280.8 ft). It is the only species in its genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, Bathykorus. The genus name comes from the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 bathy meaning "deep" and korus meaning "helmet", referring to the depth at which this species is found and to the shape of the bell. The specific name is in honour of Dr. Jean Bouillon, (1926–2009), a marine zoologist.

Description

Bathykorus bouilloni is a small gelatinous jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

 growing to around 2 cm (0.78740157480315 in) in width. It is transparent and pale blue, with 4 primary non-contractile tentacles set high above the margin of the dome-shaped bell. Lower down near the undulating margin there are 4 short secondary tentacles, each with a statocyst
Statocyst
The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, echinoderms, cephalopods, and crustaceans. A similar structure is also found in Xenoturbella. The statocyst consists of a sac-like structure containing a mineralised mass and numerous...

 on either side. There is a central circular mouth on the oral surface leading to a gastric chamber out of which lead twelve gastric pouches, three in each quadrant. The primary tentacles are solid and usually held above the bell in the direction of locomotion when the animal is foraging. The tentacles bear cnidocyte
Cnidocyte
A cnidocyte, cnidoblast, or nematocyte is a type of venomous cell unique to the phylum Cnidaria . The cnidocyte cell provides a means for them to catch prey and defend themselves from predators. Despite being morphologically simple, lacking a skeleton and usually being sessile, cnidarians prey on...

s on the aboral
Aboral
In biology, aboral surfaces are surfaces away from or opposite the mouth. The term is a compound of the Latin preposition ā, a, abs, meaning from or away from and the noun ōs, ōris n., meaning mouth. It is also the opposite of oral which is the end containing the mouth of a bilaterally...

 side. The gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...

s have not yet been observed, perhaps because they were not ripe at the time of the year when observations were made (June/July).

Distribution

Bathykorus bouilloni is found in the Arctic Ocean
Arctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...

, especially around Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

 and the north of Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. The jellyfish can only be found at an underwater depth range of 800 to 2500 m (2,624.7 to 8,202.1 ft) but it is more common in the central portion of this range.

Biology

Because of the depths at which this species is found, it is not possible to visually observe it in situ ("where it occurs") and observations are usually made by remotely operated underwater vehicles. Nor is it easy to study specimens because they tend not to survive capture by netting. Some individuals have been caught by gentle suction and brought to the surface. It has proved possible to keep these alive in dark tanks at 1 °C (33.8 °F) for a week or more.
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