Paralvinella sulfincola
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''Paralvinella sulfincola'', also known as the sulfide worm, is a species of
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 made ...
worm of the
Alvinellidae The Alvinellidae are a family of small, deep-sea polychaete worms endemic to hydrothermal vents in the Pacific Ocean. Belonging to the order Terebellida, the family contains two genera, ''Alvinella'' and ''Paralvinella''; the former genus cont ...
family that thrives on undersea hot-water
vents Vent or vents may refer to: Science and technology Biology *Vent, the cloaca region of an animal *Vent DNA polymerase, a thermostable DNA polymerase Geology *Hydrothermal vent, a fissure in a planet's surface from which geothermally heated water ...
. It dwells within tubes in waters surrounding hydrothermal vents, in close proximity to super-heated fluids reaching over . The upper thermal limit for this polychaete is unknown; however, it is unlikely they can survive in constant temperatures over . It may tentatively be named a
metazoan Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in ...
extremophile An extremophile (from Latin ' meaning "extreme" and Greek ' () meaning "love") is an organism that is able to live (or in some cases thrive) in extreme environments, i.e. environments that make survival challenging such as due to extreme temper ...
or, more specifically, a
thermophile A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the earl ...
. Their unique abilities to withstand high temperatures close to hydrothermal fluids enables them to prey upon sulphur-oxidising bacterial mats which grow close to the metal rich vent plume.


Morphology

''Paralvinella sulfincola'' colonizes smoker chimneys found near deep sea ridges in aggregations or singly upon vents. They grow up to a length of about 20-70 mm and secrete
mucous Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...
in the form of a tube with two openings. This tube serves as a home, not only for the worm, but also for a whole host of microbial organisms on which the worm feeds. The worm has a crown of branchial filaments on the anterior side of its body that it uses for
gas exchange Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a ...
. Among polychaetes, ''P. sulfincola''’s crown has the largest surface area.  The branchial crown usually peeks out when the worm is inside its tube in what is thought to be its resting state. The worm also has buccal tentacles, which it uses for feeding.


Behavior

While the worms spend most of their time inside of their tubes with their branchial crowns peeking out, they do engage in various behaviors such as the exploration of the environment surrounding their tube and occasional contact with surrounding worms. Exploration of the environment surrounding their tube involves the worm partially inside its tube. It utilizes its branchial filaments to brush across the surface of the chimney, and sometimes extends the upper parts of its body to sweep out across the tube entrance. Other times, the worm can be almost fully extended, with only its tail-end hidden inside the tube. This exploration behavior is mainly for the purpose of finding food. During these explorations, the worm’s buccal tentacles are extended over the surface of the chimney or the worm’s tube. The sweeping motion the worm exhibits is thought to free up particles from these surfaces. Direct contact with other worms comes in the form of either one worm brushing its branchial filaments against another worm or an instigator worm using its body to strike its con-specific. This contact is usually interpreted as aggressive, as both worms withdraw to their respective tubes afterwards, and is likely a way for the worms to maintain their feeding territory. In this respect, it seems that size matters, as bigger worms are able to maintain a larger area than their smaller conspecifics. The worms hardly leave their tubes, and when they did, it was mostly in response to habitat disturbance. One other possibility for worm migration is the decrease in food availability in the worm’s general area.


Habitat

''Paralvinella sulfincola'' are mostly found on the chimneys that form near the
Juan de Fuca Ridge The Juan de Fuca Ridge is a mid-ocean spreading center and divergent plate boundary located off the coast of the Pacific Northwest region of North America. The ridge separates the Pacific Plate to the west and the Juan de Fuca Plate to the east ...
on the Northwestern Pacific. Chimney formation happens in two main phases. In the first phase, hot seawater that is intensely saturated with
calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris ...
emerges from the seafloor and deposits anhydrite minerals into a porous, chimney-like structure. In the second phase, sulfide minerals replace the initial
anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...
minerals as the chimney gets thicker. ''P. sulfincola'' starts to colonize the chimney during this second phase and it contributes to the chimney’s chemical environment by forming a
marcasite The mineral marcasite, sometimes called “white iron pyrite”, is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both ...
crust on the chimney as the worms build their tubes. It is thought that the elemental sulfur found in the worms’ tube mucus react with the sulfides present to form this marcasite material. The temperatures generated on and surrounding the hydrothermal vent limit the kinds of species that can live on it: the surrounding water nears freezing temperatures, but the vent itself is a source of extreme heat. As a result, the species living on the vents must be able to tolerate a wide range of temperatures. ''P. sulfincola'' is among the most eurythermal of the marine invertebrates, with the worm remaining active at a range of . It is also able to survive up to temperatures as high as . Activity in this species seems to decrease as temperature increases. One theory for this is that food is more abundant in warmer temperatures, and so the worm does not need to forage much and can remain stationary.


See also

*
Pompeii worm ''Alvinella pompejana'', the Pompeii worm, is a species of deep-sea polychaete worm (commonly referred to as "bristle worms"). It is an extremophile found only at hydrothermal vents in the Pacific Ocean, discovered in the early 1980s off the Gal ...


References


External links


Photo gallery at NOAA Pacific Marine Environmental Laboratory
{{Taxonbar, from=Q2062259 Terebellida Thermophiles Animals living on hydrothermal vents