''Swima'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of marine

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

worms The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive catalogue and list of names of marine organisms. Content The content of the registry is edited and maintained by scien ...

found in the ocean at depths between . 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 or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low tempe ...

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

(free-swimming) genus has modified

bioluminescent Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some fungi, microorganisms inc ...

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, 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 r ...

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 i ...

'', 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 bathypela ...

Discovery

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

trenches A trench is a type of excavation or depression in the ground that is generally deeper than it is wide (as opposed to a swale or a bar ditch), and narrow compared with its length (as opposed to a simple hole or pit). In geology, trenches res ...

Monterey Bay Monterey Bay is a bay of the Pacific Ocean located on the coast of the U.S. state of California, south of the San Francisco Bay Area. San Francisco itself is further north along the coast, by about 75 miles (120 km), accessible via California S ...

, off the coast of

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

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 International_Code_of_Zoological_Nomenclature, 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 spe ...

) * ''

Swima fulgida ''Swima'' is a genus of marine polychaete Annelid, worms found in the ocean at depths between . Even if they are agile swimmers, they are often seen hanging immobile in the water column as they are neutrally buoyant. This Bathyal zone, deep ocean ...

'' Osborn, Haddock & Rouse, 2011 (Shining Bomber) * '' Swima tawitawiensis'' 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 cephalopods, and other invertebrates. Annelids only possess one nuchal organ, although the nature of the grooving may make it appea ...

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 languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

, referring to the animal's ability to swim.

References

External links

* Terebellida {{annelid-stub