The Echinasteridae are a

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

of starfish in the monotypic order

Spinulosida The Spinulosida are an order of sea stars containing at least 120 species in seven genera and one family. Spinulosids completely lack pedicellariae and have a delicate skeletal arrangement. Their name comes from the presence of numerous low spi ...

. The family includes eight genera and about 133 species found on the seabed in various habitats around the world.

Taxonomy

Echinasteridae contains eight genera and about 133 species. The two genera '' Echinaster'' and ''

Henricia ''Henricia'' is a large genus of slender-armed sea stars belonging to the family Echinasteridae. It contains about fifty species. The sea stars from this genus are ciliary suspension-feeders, filtering phytoplankton. Species According to the Wo ...

'' are the most speciose, forming

species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

es. ''Echinaster'' has a largely tropical distribution and occurs in shallow seas including continental shelves, while ''Henricia'' is

cosmopolitan Cosmopolitan may refer to: Food and drink * Cosmopolitan (cocktail), also known as a "Cosmo" History * Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953 Hotels and resorts * Cosmopoli ...

, occurring mostly in cold waters, including polar habitats and abyssal locations. '' Aleutihenricia'' and '' Odontohenricia'' are native to the northeastern Pacific Ocean, in the vicinity of the

Aleutian Islands The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a chain of 14 large v ...

Characteristics

Echinasterids are mostly five-armed starfish with thick but small discs, and long, slender, often cylindrical arms. The cuticle is covered on both the aboral (upper) and oral (lower) surfaces by a latticework of ossicles which are either flattened or rounded plates, or pseudopaxilliform (peglike) plates with broad bases. The mouth is surrounded by tight-fitting triangular plates. The pores through which the

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on br ...

project are small and the plates on either side of the ambulacral grooves are angular and bear spines. Echinasterids do not have

pedicellaria A pedicellaria (plural: pedicellariae) is a small wrench- or claw-shaped appendage with movable jaws, called valves, commonly found on echinoderms (phylum Echinodermata), particularly in sea stars (class Asteroidea) and sea urchins (class Echi ...

Ecology

Echinasterids are epifaunal animals that live on the seabed, on rock, sand, gravel or mud. They graze on encrusting invertebrates such as

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...

tunicate A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time ...

s and

molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...

, as well as feeding on detritus. Additionally, ''Echinaster'' uses cilia to create a current to draw

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

and organic particles into its mouth. ''Henricia'' is a scavenger and a filter feeder. The sexes are separate in these starfish. The eggs are large and yolky and development is by way of brachiolaria larvae. In some species these are

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

ic, but in others, the females brood their young in a brood chamber under their arms. '' Echinaster luzonicus'' is renowned for shedding its arms in a process known as

autotomy Autotomy (from the Greek ''auto-'', "self-" and ''tome'', "severing", αὐτοτομία) or self-amputation, is the behaviour whereby an animal sheds or discards one or more of its own appendages, usually as a self-defense mechanism to elude ...

, being then able to regenerate a new disc from a single arm. This is a form of asexual reproduction and ''E. luzonicus'' is not known to reproduce in any other way. Another echinasterid that reproduces asexually is '' Henricia sexradiata'', but in this case, the disc also splits apart.

Genera

The following genera are recognised by the

World Register of Marine Species 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. Content The content of the registry is edited and maintained by scientific specialis ...

: * '' Aleutihenricia'' Clark & Jewett, 2010 * '' Dictyaster'' Wood-Mason & Alcock, 1891 * '' Echinaster'' Müller & Troschel, 1840 * ''

'' Gray, 1840 * '' Metrodira'' Gray, 1840 * '' Odontohenricia'' Rowe & Albertson, 1988 * '' Plectaster'' Sladen, 1889 * '' Rhopiella'' Fisher, 1940

Gallery

Echinaster sepositus Linosa 092.jpg, ''

Echinaster sepositus ''Echinaster sepositus'', the Mediterranean red sea star (sometimes only red sea star, but this name is also used for other species), is a species of starfish from the East Atlantic, including the Mediterranean Sea.Villamor, A.; and M. A. Becerr ...

'' Reticulated starfish at Pinnacle PB022214.JPG, '' Henricia ornata'' Plectaster decanus Mosaic seastar PC259791.JPG, '' Plectaster decanus''

References

{{Taxonbar, from=Q146640 Echinoderm families