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

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

starfish Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Luidiidae found in the northeastern

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

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 describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Thi ...

(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 an industrial 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 di ...

. 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 (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s or

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

Distribution

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

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

to the Galapagos Islands and

Nicaragua Nicaragua, officially the Republic of Nicaragua, is the geographically largest Sovereign state, country in Central America, comprising . With a population of 7,142,529 as of 2024, it is the third-most populous country in Central America aft ...

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 () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...

, polychaete worms,

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 cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...

s 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 starfish, sea star in the Family (biology), family Asteropseidae found at depths to off the western seaboard of North America. It was first species description, described to science by Adolph Ed ...

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

References

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