''Swima'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of marine

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ...

worms Worms may refer to: *Worm, an invertebrate animal with a tube-like body and no limbs Places *Worms, Germany, a city ** Worms (electoral district) * Worms, Nebraska, U.S. *Worms im Veltlintal, the German name for Bormio, Italy Arts and entertai ...

found in the ocean at depths between 1,800 and 3,700 meters (5,900 and 12,140 feet). Even if they are agile swimmers, they are often seen hanging immobile in the water column as they are neutrally buoyant. This

deep ocean The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 metres (656 feet) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combin ...

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

(free-swimming) genus has modified

bioluminescent Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some b ...

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...

s that can be cast off from an individual. These discarded gills somewhat resemble green "bombs" that remain illuminated for several seconds after they have been discarded. It is thought that this is a defensive mechanism rather than reproductive, as it is seen in both mature and juvenile individuals. And because they are eyeless, communicating with light would be difficult. ''Swima'' worms are closely related to the recently discovered genus ''

Teuthidodrilus ''Teuthidodrilus samae'', dubbed as the squidworm, is a species of acrocirrid marine annelid worms. It is free-swimming and can be found in the deep sea water column at depths of . It feeds on marine snow and can grow to about in length and ...

'', another pelagic cirratuliform of the

bathyal zone The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypel ...

Discovery

The first specimens of the genus ''Swima'' were discovered in the deep trenches of

Monterey Bay Monterey Bay is a bay of the Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica ...

, off the coast of

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

Taxonomy

There are currently three species recognised within the ''Swima'': * '' S. bombiviridis'' Osborn, Haddock, Pleijel, Madin & Rouse, 2009 (Green Bomber Worm or Bombardier Worm),

(

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

) * ''

Swima fulgida ''Swima'' is a genus of marine polychaete worms found in the ocean at depths between 1,800 and 3,700 meters (5,900 and 12,140 feet). Even if they are agile swimmers, they are often seen hanging immobile in the water column as they are neutrally ...

'' Osborn, Haddock & Rouse, 2011 (Shining Bomber) * ''

Swima tawitawiensis ''Swima'' is a genus of marine polychaete worms found in the ocean at depths between 1,800 and 3,700 meters (5,900 and 12,140 feet). Even if they are agile swimmers, they are often seen hanging immobile in the water column as they are neutrally ...

'' Osborn, Haddock & Rouse, 2011 (Tawi-Tawi Bomber))

Anatomy and physiology

Animals of the ''Swima'' are characterized by a thick gelatinous sheath, transparent body, simple

nuchal organ The nuchal organ is a ciliated pit or groove present at the posterior end of the prostomium of annelid worms, some cephalopod A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, o ...

s, a single medial subulate branchia, and four pair of small segmental branchiae modified as elliptical, bioluminescent sacs.

Etymology

The genus name, ''Swima'', is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

, referring to the animal's ability to swim.

References

External links

* Terebellida {{annelid-stub