''Bathykorus bouilloni'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

hydrozoa Hydrozoa (hydrozoans; ) are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specializ ...

n first described in 2010. It is a deep-sea species found in the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...

, and appears to be common at depths below .''Bathykorus bouilloni'' Raskoff , 2010
Arctic Ocean Diversity. Retrieved November 7, 2011. It is the only species in the monotypic

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

''Bathykorus''. The genus name comes from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''bathy'' meaning "deep" and ''korus'' meaning "helmet", referring to the depth at which this species is found and to the shape of the bell. Its helmet-like appearance bears a resemblance to the helmet of

Darth Vader Darth Vader is a fictional character in the ''Star Wars'' franchise. The character is the central antagonist of the original trilogy and, as Anakin Skywalker, is one of the main protagonists in the prequel trilogy. ''Star Wars'' creator George ...

, giving it the nickname Darth Vader jellyfish. The specific name is in honour of Dr.

Jean Bouillon Jean Bouillon (20 December 1926 – 29 March 2009) was a Belgian marine biologist and expert on Hydrozoa. Biography Jean Bouillon was born in Uccle, Belgium. He worked from 1955 to 1991 as a professor at the Université libre de Bruxelles. He wa ...

, (1926–2009), a marine zoologist.

Description

''B. bouilloni'' is a small, gelatinous hydrozoan growing to around in width. It is transparent and pale blue, with four primary noncontractile tentacles set high above the margin of the dome-shaped bell. Lower down near the undulating margin are four short secondary tentacles, each with a

statocyst The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, and crustaceans. A similar structure is also found in ''Xenoturbella''. The statocyst cons ...

on either side. The central circular mouth on the oral surface leads to a gastric chamber out of which lead 12 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 A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this ce ...

s on the

aboral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

side. The

gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sper ...

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

''B. bouilloni'' is found in the

, especially around

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

and the north of

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

. The jellyfish can only be found at an underwater depth range of , but it is more common in the middle of this range.

Biology

Because of the depths at which this species is found, it is not possible to visually observe it ''

in situ ''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...

'', and observations are usually made by

remotely operated underwater vehicle A remotely operated underwater vehicle (technically ROUV or just ROV) is a tethered underwater mobile device, commonly called ''underwater robot''. Definition This meaning is different from remote control vehicles operating on land or in the ai ...

s. 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 and it has proved possible to keep these alive in dark tanks at 1 °C (34 °F) for a week or more.

References

Aeginidae Hydrozoan genera Monotypic cnidarian genera {{Hydrozoa-stub