Psamathini

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Psamathini
Scientific classification
Kingdom: Animalia
Phylum: Annelida
Class: Polychaeta
Subclass: Palpata
Order: Aciculata
Suborder: Phyllodocida
Family: Hesionidae
Subfamily: Hesioninae
Tribe:Psamathini
Pleijel, 1998
Genera

5-8, see text

Psamathini are a tribe of phyllodocid "bristle worms" (class Polychaeta) in the family Hesionidae. They are (like almost all polychaetes) marine organisms; most are found on the continental shelf, but some have adapted to greater depths down to the abyssal plain. [1]

In biology, a tribe is a taxonomic rank above genus, but below family and subfamily. It is sometimes subdivided into subtribes.

Phyllodocida order of annelid worms

Phyllodocida is an order of polychaete worms in the subclass Aciculata. These worms are mostly marine though some are found in brackish water. Most are active benthic creatures, moving over the surface or burrowing in sediments, or living in cracks and crevices in bedrock. A few construct tubes in which they live and some are pelagic, swimming through the water column. There are estimated to be about 3,500 species in the order.

In biological classification, class is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. Other well-known ranks in descending order of size are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order.

Their dorsal cirri alternate, and they usually lack facial tubercles. Most have prolonged teeth on the chaetal blades. 5 genera are placed in the Psamathini with certainty, and three further ones are often included here too in recent times, to make this tribe refer to a distinct clade of polychaetes: [2]

A chaeta or cheta is a chitinous bristle or seta found on an insect, arthropod or annelid worms such as the earthworm, although the term is also frequently used to describe similar structures in other invertebrates. The plural form is chaetae or chetae.

Clade A group of organisms that consists of a common ancestor and all its lineal descendants

A clade, also known as monophyletic group, is a group of organisms that consists of a common ancestor and all its lineal descendants, and represents a single "branch" on the "tree of life".

Footnotes

  1. ↑ Pleijel et al. (2008)
  2. ↑ Pleijel et al. (2008), WoRMS (2008)

Related Research Articles

Polychaete Class of annelids

{{Paraphyletic group Support and Locomotion Polychaeta. Polychaetes provide a classic example of the employment of coelomic spaces as a hydrostatic skeleton for body support. Coupled with the well developed musculature, the metameric body plan, and the parapodia, this hydrostatic quality provides the basis for understanding locomotion in these worms. We begin a survey of locomotor patterns by examining Nereis, an errant, homonomous polychaete. Keep in mind that in such polychaetes the intersegmental septa are functionally complete, and thus the coelomic spaces in each segment can be effectively isolated hydraulically from each other. Modifications on this fundamental arrangement are discussed later. In addition to burrowing, Nereis can engage in three basic epibenthic locomotor patterns: slow crawling, rapid crawling, and rather inefficient swimming. All of these methods of movement depend primarily on the bands of longitudinal muscles, especially the larger dorsolateral bands, and on the parapodial muscles. The circular muscles are relatively thin and serve primarily to maintain adequate hydrostatic pressure within the coelomic compartments. Each method of locomotion in Nereis involves the antagonistic action of the longitudinal muscles on opposite sides of the body in each segment. During movement, the longitudinal muscles on one side of any given segment alternately contract and relax in opposing synchrony with the action of the muscles on the other side of the segment. Thus, the body is thrown into undulations that move in metachronal waves from posterior to anterior. Variations in the length and amplitude of these waves combine with parapodial movements to produce the different patterns of locomotion. The parapodia and their chaetae are extended maximally in a power stroke as they pass along the crest of each metachronal wave. Conversely, the parapodia and chaetae retract in the wave troughs during their recovery stroke. Thus, the parapodia on opposite sides of any given segment are exactly out of phase with one another. When Nereis is crawling slowly, the body is thrown into a high number of metachronal undulations of short wavelength and low amplitude. The extended parapodial chaetae on the wave crests are pushed against the substratum and serve as pivot points as the parapodium engages in its power stroke. As the parapodium moves past the crest, it is retracted and lifted from the substratum as it is brought forward during its recovery stroke. The main pushing force in this sort of movement is provided by the parapodial muscles. During rapid crawling, much of the driving force is provided by the longitudinal body wall muscles in association with the longer wavelength and greater amplitude of the body undulations, which accentuate the power strokes of the parapodia. Nereis can leave the substratum to engage in a rather inefficient swimming behavior. In swimming, the metachronal wavelength and amplitude are even greater than they are in rapid crawling. When watching a nereid swim, however, one gets the impression that the “harder it tries” the less progress it makes, and there is some truth to this. The problem is that, even though the parapodia act as paddles pushing the animal forward on their power strokes, the large metachronal waves continue to move from posterior to anterior and actually create a water current in that same direction; this current tends to push the animal into reverse. The result is that Nereis is able to lift itself off the substratum, but then largely thrashes about in the water. This behavior is used primarily as a short-term mechanism to escape benthic predators rather than as ameans to get from one place to another. With these basic patterns and mechanisms in mind, we consider a few other methods of locomotion in polychaetes. Nephtys superficially resembles Nereis, but its methods of movement are significantly different. Although Nephtys is less efficient than Nereis at slow walking, it is a much better swimmer; it is also capable of effective burrowing in soft substrata. The large, fleshy parapodia serve as paddles, and, when swimming, Nephtys does not produce long, deep metachronal waves. Rather, the faster it swims, the shorter and shallower the waves become, thus eliminating much of the counterproductive force described for Nereis. When initiating burrowing, Nephtys swims head-first into the substratum, anchors the body by extending the chaetae laterally from the buried segments, and then extends the proboscis deeper into the sand. A swimming motion is then employed to burrow deeper into the substratum. In contrast to the above descriptions, scale worms have capitalized on the use of their muscular parapodia as efficient walking devices. The body undulates little if at all, and there is a corresponding reduction in the size of the longitudinal muscle bands and their importance in locomotion. In fact, these worms depend almost entirely on the action of the parapodia for walking; polynoids cannot swim. Many of the highly efficient burrowers have secondarily lost most of the intersegmental septa, or have septa that are perforated. The loss of complete septa means that segments are not of constant volume; in other words, a loss of coelomic fluid from one body region causes a corresponding gain in another. These polychaetes have reduced parapodia. The chaetae, or simply the surface of the expanded portions of the body, serve as anchor points, while the burrow wall provides an antagonistic force resisting the hydraulic pressure. In Polyphysia, peristaltic waves move constricted body regions forward while the anchored parts provide leverage. The constricted areas are reduced both in diameter and in length by simultaneous contraction of both the circular and the longitudinal muscles. Arenicola burrows first embedding and anchoringlongitudinal Arenicola burrows by first embedding and anchoring the anterior body region in the substratum. The anchoring is accomplished by contracting the circular muscles of the posterior portion of the body, thus forcing coelomic fluid anteriorly and causing the first few segments to swell. Then the posterior longitudinal muscles contract, thereby pulling the back of the worm forward. To continue the burrowing, a second phase of activity is undertaken. As the anterior circular muscles contract and the longitudinal bands relax, the posterior edges of each involved segment are protruded as anchor points to prevent backward movement; the proboscis is thrust forward, deepening the burrow. Then the proboscis is retracted, the front end of the body is engorged with fluid, and the entire process is repeated. Different burrowing mechanisms are known among other polychaetes. For example, Glycera, a long, sleek worm, burrows rapidly using its large, muscular proboscis almost exclusively. The proboscis is thrust into the substratum and swelled; then the body is drawn in by contraction of the proboscis muscles. Most tube-dwelling polychaetes are heteronomous and have rather soft bodies and relatively weak muscles. The parapodia are reduced, so the chaetae are used to position and anchor the animal in its tube. Movement within the tube is usually accomplished by slow peristaltic action of the body or by chaetae movements. When the anterior end is extended for feeding, it may be quickly withdrawn by special retractor muscles while the unexposed portion of the body is anchored in the tube. Polychaete tubes provide protection as well as support for these soft-bodied worms, and also keep the animal oriented properly in relation to the substratum. Some polychaetes build tubes composed entirely of their own secretions. Most notable among these tube builders are the serpulids and spirorbids, which construct their tubes of calcium carbonate secreted by a pair of large glands near a fold of the peristomium called the collar. The crystals of calcium carbonate are added to an organic matrix; the mixture is molded to the top of the tube by the collar fold and held in place until it hardens. Some sabellids produce parchment-like or membranous tubes of organic secretions molded by the collar. Others, such as Sabella, mix mucous secretions with size selected particles extracted from feeding currents, then lay down the tube with this material. Numerous other polychaete groups form similar tubes of sediment particles collected in various ways and cemented together with mucus. A few polychaetes are able to excavate burrows by boring into calcareous substrata, such as rocks, coral skeletons or mollusc shells. In extreme situations, the activity of the polychaetes may have deleterious effects on the “host.” For example, species of Polydora (Spionidae) can cause serious damage to commercially raised oysters. Many sedentary polychaetes use modifications of the basic locomotor actions described above to provide means of moving water through their tubes or burrows. Some of these modifications are discussed in the sectionon feeding.

<i>Osedax</i> genus of annelids

Osedax is a genus of deep-sea siboglinid polychaetes, commonly called boneworms, zombie worms, or bone-eating worms. Osedax is Latin for "bone-eating". The name alludes to how the worms bore into the bones of whale carcasses to reach enclosed lipids, on which they rely for sustenance.

Trochidae family of molluscs

The Trochidae, common name top-snails or top-shells, are a taxonomic family of very small to large sea snails, marine gastropod molluscs in the clade Vetigastropoda.

Boarmiini

The Boarmiini are a large tribe of geometer moths in the Ennominae subfamily.

Polynoidae Family of annelids

Polynoidae is a family of scaled Polychaete worms known as "scale worms". More than 900 species are currently recognised belonging to 18 subfamilies and 167 genera. They are active hunters, but generally dwell in protected environments such as under stones. The group is widely distributed from shallow intertidal waters to hadal trenches. They are the most diverse group of polychaetes in terms of genus number and second most diverse in terms of species number.

Terebellida suborder of annelids

Terebellida make up an order of the Polychaeta class, commonly referred to as "bristle worms". Together with the Sabellida, the Spionida and some enigmatic families of unclear taxonomic relationship, they make up the subclass Canalipalpata, one of the three main clades of polychaetes. Like most polychaetes, almost all members of the Terebellida are marine organisms. Most are small, sessile detritivores which live in small tubes they build from mud or similar substrate, or burrow in the sand. Their central nervous system displays characteristic apomorphies.

Nacophorini tribe of insects

The Nacophorini are one of the smaller tribes of geometer moths in the subfamily Ennominae. They are the most diverse Ennominae of Australia and are widespread in the Americas. If the African genera tentatively placed herein indeed belong here, the distribution of the Nacophorini is distinctly Gondwanan, with their probable origin either of Australia, South America or even Antarctica. In Eurasia, they are rare by comparison.

<i>Odostomia</i> genus of molluscs

Odostomia is the most speciose genus of minute sea snails, pyramidellid gastropod mollusks. This genus is placed in the family Pyramidellidae in the subfamily Odostomiinae. There are several hundred species in this diverse genus

Ampharetidae family of annelids

Ampharetidae are a family of terebellid "bristle worm". As such, they belong to the order Canalipalpata, one of the three main clades of polychaetes. They appear to be most closely related to the peculiar alvinellids (Alvinellidae) which inhabit the deep sea, and somewhat less closely to the well-known trumpet worms (Pectinariidae). These three appear to form one of the main clades of terebellids.

Hesioninae are a subfamily of phyllodocid "bristle worms". They are marine organisms; most are found on the continental shelf.

<i>Hesionidae</i> Family of annelids

Hesionidae are a family of phyllodocid "bristle worms". They are marine organisms. Most are found on the continental shelf; Hesiocaeca methanicola is found on methane ice, where it feeds on bacterial biofilms.

Swima is a genus of polychaete worm that lives in the deep ocean. 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. Animals of the genus Swima are closely related to the recently discovered genus Teuthidodrilus, another pelagic cirratuliform of the bathyal zone.

Areneidae is a family of sea snails, marine gastropod mollusks in the clade Vetigastropoda.

<i>Californiconus</i> genus of molluscs

Californiconus is a genus of sea snails, marine gastropod mollusks. The experts at WoRMS place this group of species in the family Conidae, the cone snails, but some other experts placed previously the genus in a proposed family, the Conilithidae. This is a monotypic genus.

<i>Amphinomidae</i> Family of annelids

Amphinomidae, also known as the bristle worms or sea mice, are a family of marine polychaetes, many species of which bear chaetae mineralized with carbonate. The best-known amphinomids are the fireworms, which can cause great pain if their toxin-coated chaetae are touched or trodden on. Their relationship to other polychaete groups is somewhat poorly resolved.

Annelid Phylum of segmented worms

The annelids, also known as the ringed worms or segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments.

<i>Ophryotrocha</i> genus of annelids

Ophryotrocha is a genus of marine polychaete worms in the family Dorvilleidae.

A genus of polychaete thought to be related to the Nerillidae.

References

<i>Zoological Journal of the Linnean Society</i> scientific journal

The Zoological Journal of the Linnean Society is a monthly peer-reviewed scientific journal covering zoology published by Oxford University Press on behalf of the Linnean Society. The editor-in-chief is Maarten Christenhusz. It was established in 1856 as the Journal of the Proceedings of the Linnean Society of London. Zoology and renamed Journal of the Linnean Society of London, Zoology in 1866, obtaining its current title in 1969.

Digital object identifier Character string used as a permanent identifier for a digital object, in a format controlled by the International DOI Foundation

In computing, a Digital Object Identifier or DOI is a persistent identifier or handle used to identify objects uniquely, standardized by the International Organization for Standardization (ISO). An implementation of the Handle System, DOIs are in wide use mainly to identify academic, professional, and government information, such as journal articles, research reports and data sets, and official publications though they also have been used to identify other types of information resources, such as commercial videos.

The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive list of names of marine organisms.


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