''Luidia foliolata'', the sand star, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of starfish in the

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

Luidiidae found in the northeastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

on sandy and muddy seabeds at depths to about .

Description

The sand star has a small disc and five long, flattened arms with tapering tips. It can grow to a diameter of , and is a grey, greenish-grey, or pale brown colour, sometimes speckled with white. The arms have rows of large marginal plates, each with several spines, but these are not visible from the

aboral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

(upper) side. The tube feet have no suckers, but instead end with blunt points. The sand star could be confused with '' Astropecten verrilli'', but in that species, the large marginal plates are visible from above. This starfish seems to be easily damaged, and often breaks in pieces if raised from the seabed by

trawling Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different spec ...

. Even when brought up intact, it often has missing or regenerating arms, perhaps the result of attacks by predatory

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

s or

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

Distribution

The sand star is found at depths to on soft substrates in the northeastern Pacific Ocean, with a range extending from

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

to the Galapagos Islands and

Nicaragua Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the cou ...

Behaviour

The sand star is well-camouflaged on the sandy and muddy seabeds where it is found, and is often half-covered with sediment. It can create a shallow depression and work its way under the

bivalve molluscs Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

polychaete worms 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 m ...

brittle star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

s, and sea cucumbers on which it feeds. Unlike some other starfish, it cannot evert its stomach, so is limited to smaller-sized prey. It is agile, and can right itself rapidly if turned upside down. The long, pointed tube feet are specially adapted for movement over soft sediments, but lose traction if the sand star tries to scale steeply sloping rocks. It is a fast traveller, and can move across the seabed at the rate of per minute, many times faster than slow species such as the

leather star The leather star (''Dermasterias imbricata'') is a sea star in the family Asteropseidae found at depths to off the western seaboard of North America. It was first described to science by Adolph Eduard Grube in 1857. Description The leather st ...

(''Dermasterias imbricata''), which can only traverse in a minute.

References

{{Taxonbar, from=Q3276426 foliolata Fauna of the Pacific Ocean Animals described in 1866 Taxa named by Adolph Eduard Grube