Swima bombiviridis is a pelagic marine polychaete worm, characterized by its transparent foregut and its more than 15% uncorrected cytochrome oxidase I (COI) distance from all other Swima species. S. bombiviridis displays the distinguishing green bioluminescence that occurs in all the “bomb”-bearing species (luminescent structures are colloquially termed "bombs" because they suddenly burst into light when released by the animal, glowing intensely for many seconds then slowly diminishing).
[Osborn et al. 2009]
Swima bombiviridis is the type species of the genus Swima, which was only described in 2009. Swima bombiviridis and its close relatives are pelagic marine polychaete worms spending most or all of their life living in the deep sea at depths greater than 1800 meters. Some, like S. bombiviridis, live well above the bottom and presumably never land and are exceptional swimmers, hence the generic name. The common name for this species is the ‘green bomber’ owing to a series of green spheres attached just behind the head that are easily shed by the animal when it is disturbed. These are also the basis for the specific epithet, bombiviridis, which is Latin for green bombs. Once detached, the bombs will glow with green light for up to a minute. Swima bombiviridis belongs to the polychaete family Acrocirridae. Nearly all other acrocirrids are benthic, living in sediments or under rocks from shallow water down to the deep sea. An evolutionary analysis of acrocirrids has shown that Swima bombiviridis and its pelagic relatives evolved from benthic acrocirrid ancestors and share many morphological features with other acrocirrids, although some features appear to have evolved to suit their pelagic lifestyle. Like its benthic relatives, Swima bombiviridis has a pair of grooved palps that it presumably uses for feeding. However, while other acrocirrids usually have four pairs of elongate branchiae (gills) behind the head that are easily detachable, in S. bombiviridis and some of its other pelagic relatives these gills appear to have been evolutionarily transformed to become detachable bioluminescent orbs, the ‘bombs’. These may well not function as branchiae any more and instead these animals have evolved new structures that appear to be branchiae. Swima and its swimming relatives also have elongate paddle-like chitinous chaetae in bundles along their bodies that are quite different from those of their benthic relatives and are almost certainly for use in swimming. (Osborn et al. 2009; Osborn et al. 2011; Osborn and Rouse 2011)
Body: Completely transparent body with 25 chaetigers with parapodial lobes and numerous long chaetae. The bottom end is smoothly tapered with a thick gelatinous sheath through which narrow, clavate papillae extend. Yellow, small papillae extend from the body wall through the sheath, especially numerous on parapodia.
Head: The head has no eyes and consists of the prostomium, peristomium, and at least two achaetous segments possessing three forms of branchiae. Prostomium consists of tissue supporting a pair of low, ciliated, oblique ridges that form nuchal organs. Grooved frontal palps are transparent-yellow, tapered, and coiling at tips. Peristomium surrounds prostomium completely. Buccal organ is unarmed, bilobed, and form eversible lateral lips, which lack pigment.
Branchiae: There are three forms of branchiae: 1) single, long (reach at least second chaetiger), tapered median branchia, transparent to white, 2) more than 40, fine, digitiform respiratory branchiae present across surface in tightly packed row, yellow, 3) four elliptical lobes attached to achaetous segments and one on first chaetiger.
Bombs: The bombs are segmentally-occurring, elliptical, lobe-like branchiae, greenish-yellow in life, autofluoresce the same color, produce bioluminescence, and often autotomized. The "bombs" are 0.7 to 1.1 mm in length. Scars from bombs are distinguishable as slightly raised rings of thickened tissue, colloquially referred to as “bomb bays."
Chaetigers: Noto- and neuropodal lobes form a single, nearly smooth projection with a higher concentration of fine clavate papillae compared to rest of body surface. One to four clavate papillae have a lollipop shape and project well beyond gelatinous sheath, with solid tips. High magnification reveals fine whorls of spines along entire length of chaetae giving especially distal tips a segmented appearance. Distal edge of spinous whorls project as frayed edges on worn and longest chaetae. The middle chaetigers 4–6 each have a pair of low, hollow papillae (gonopore) at base of neuropodia.
Internal description: Internal structures are visible through transparent body wall and gelatinous sheath. The double nerve cord, with two pairs of fused ganglia per segment, diverges just behind the peristomium to surround buccal organ, and fuses again just posterior to palp attachment. A single pair of large semitransparent nephridia reach back as far as second chaetiger, fold back and then narrow to lead to the nephridiopores. The gut runs from buccal organ straight for one third body length at which point it forms a wide, single loop, after which it broadens and continues back to the twelfth chaetiger before narrowing and turning again. Gut continues to near first loop then folds rearward and continues directly to pygidium. The heart body is first distinguishable near the digitiform branchiae, extending through the front third of body until it appears to fuse with the broadened portion of gut. Gonads form around the middle chaetigers 4-6.
[Osborn et al. 2009]
Holotype: 15 mm
Bombs: vary in size from 0.6–1.2 mm
[Osborn et al. 2009]
Swima (genus): Swimming acrocirrids with more than 30 long chaetae per parapodium, no eyes, non-retractable head, and with a gelatinous sheath penetrated by club-shaped papillae. One or more lollipop-shaped papillae project well beyond the gelatinous sheath. Nuchal organs are oblique, slightly raised ridges to spiral and branched structures above the body wall. Four pairs of branchiae may be modified as ellipsoid bioluminescent structures or long with tapered tips and are easily lost, leaving obvious circular scars.
Swima bombiviridis (species): Swima with a transparent gut, a thick, transparent gelatinous sheath penetrated throughout by narrow club-shaped papillae, simple noto- and neurochaetae, and three achaetous anterior segments supporting ellipsoid, bioluminescent, derived branchiae that are less than 1.5 mm in length.
[Osborn et al. 2009]
Swina bombiviridis is found off the central California coast at 2732–3600 meters depth, from 1–444 meters above the seafloor. Similar animals were observed but not collected off the Oregon coast and Gulf of California. Worms were not observed on the seafloor, although they were sometimes observed within sight of it. Worms were most often observed hanging horizontally in the water column with the palps hanging forward and downward over the buccal organ. Nineteen specimens of Swima bombiviridis were collected by the ROV Tiburon outside Monterey Bay, California (2734–3497 meters, 34–36º N, 121–122º W) since the first discovery in 2001.
Holotype: collected off the central coast of California on 7 April, 2005 at 3054 m in 3498 m deep water, deposited at the Benthic Invertebrate Collection of Scripps Institution of Oceanography (SIO BIC A1282; 36º 19.80ʼ N, 122º 53.99ʼ W).
SIO BIC A1281 and A1284 5 June 2005 3744 meters, 36º43.98ʼ N, 123º 41.93ʼ W
SIO BIC A1283 28 November 2007 3019 meters, 35º 50.42ʼ N, 122º 40.13ʼ W
SIO BIC A1634–1635 20-21 September 2005 3325–3442 meters, 36º 19.80ʼ N, 122º 53.99ʼ W
SIO BIC A1636 2 October 2006 2732 meters, 35º 37.99ʼ N, 122º 44.00ʼW
SIO BIC A1637 2 November 2007 3411 meters, 36º 19.39ʼ N, 122º 54.18ʼ W
SIO BIC A1638 26 February 2009 3600 meters, 35º 7.61ʼ N, 122º 55.60ʼ W
[Osborn et al. 2009]
Life History and Behavior
Bioluminescence is a known defensive tool in polychaetes. The bioluminescent bombs seen in some Swima species is not associated with reproduction, but instead serves a defensive function. The nature of the bioluminescent structures, observation of autotomization of structures in response to stimulation at multiple points along the body, luminescence of the structures after release, and the presence of bioluminescence in immature and mature specimens supports this hypothesis. Bioluminescence is seen as a steady glow from bombs that has been autotomized from the body of the animal. Bombs can be triggered to produce light by gently squeezing them with forceps. The glow of an individual bomb lasts several seconds.
Swimming: The species, like others in the clade, swim by lateral undulation of the body coupled with expansion on the power stroke and contraction on the recovery stroke of the chaetal fans. Swimming is observed in both forward and rearward directions. When disturbed, direction of initial escape is always rearward.
[Osborn et al. 2009]
Molecular Biology and Genetics
Barcode data: Swima bombiviridis
No available public DNA sequences.
Download FASTA File
Statistics of barcoding coverage: Swima bombiviridis
Public Records: 8
Specimens with Barcodes: 8
Species With Barcodes: 1
Swima bombiviridis is a worm species that lives in the deep ocean. It is also known as the Green Bomber Worm or Bombardier Worm. This deep ocean pelagic (free-swimming) annelid has modified bioluminescent gills 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. This species was the first of its genus, Swima, to be discovered, and was the only one with a formal scientific name as of 2010. The genus name, Swima, is derived from the Latin, referring to the animal's ability to swim. The species name, bombiviridis, is derived from the Latin prefix bombus, meaning humming or buzzing (from which the English word bomb is derived), and the suffix viridis, which is Latin for the color green. Swima bombiviridis therefore translates to "swimming green bomber".
- Osborn KJ, Haddock SHD, Pleijel F, Madin LP, Rouse GW (2009). "Deep-sea, swimming worms with luminescent "bombs"". Science 325 (5943): 964. doi:10.1126/science.1172488.
- Moskowitz, Clara (20 August 2009). "Sea Creature Releases Glowing Decoy 'Bombs'". LiveScience. Retrieved 2009-11-14.
- International Institute for Species Exploration (2010). "Bombardier Worm". Top 10 New Species – 2010. Tempe, Arizona: Arizona State University.
- Osborn KJ, Rouse GW (2010). "Phylogenetics of Acrocirridae and Flabelligeridae". Zoologica Scripta 40 (2): 204–219. doi:10.1111/j.1463-6409.2010.00460.x.
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