''Centrostephanus longispinus'', the hatpin urchin, is a

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) ...

in the family

Diadematidae The Diadematidae are a family of sea urchins. Their tests are either rigid or flexible and their spines are long and hollow. * '' Astropyga'' Gray, 1825 **''Astropyga radiata'' ( Leske, 1778), extant **''Astropyga pulvinata'' ( Lamarck, 1816), ...

. There are two subspecies, ''Centrostephanus l. longispinus'', found in the eastern Atlantic and Mediterranean Sea and ''Centrostephanus l. rubricingulus'', found in the western Atlantic.

Taxonomy

In 1940, Mortenson believed that ''C. longispinus'' and ''C. rubicingulus'' were closely related species but that they could be distinguished because ''C. longispinus'' has smaller and fewer secondary interambulacral tubercles. In 1975, Fell re-examined the genus but was unable to find sufficient differences to justify separating them into two species. He suggested that ''C. rubicingulus'' should be considered a sub-species of ''C. longispinus''. Nor could he reliably distinguish the pair from ''C. besnardi'' except by the location from which they had been collected (''C. besnardi'' is from the eastern Pacific). He was also unable to distinguish between juveniles of '' C. coronatus'' and juveniles of the other species.

Description

''Centrostephanus longispinus'' has a small central

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

and spines up to in length. These are toxic and can cause a painful sting. The spines are of varying length and are mobile and used for locomotion. There are a number of club-shaped spines on the oral (lower) surface, a characteristic that this species shares with ''C. besnardi'' and ''C. coronatus'' but not other members of the genus. These spines are reddish brown and are tipped with purple or pink pigment. The subspecies ''C. l. longispinus'' has spines banded in purple on a pale green, buff or whitish background. Juvenile ''C. l. rubricingulus'' have reddish-brown spines on a pale background while adults have either spines banded in brown on pale brown or uniformly dark-colored spines. It has been shown that ''C. longispinus'' has

chromatophore Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, ...

s (pigment bearing structures in cells) which are sensitive to light. By changing their shape, these alter the color of the animal, which is changed from a night-time black to a daytime greyish brown.

Distribution and habitat

''Centrostephanus longispinus'' occurs on the continental shelf on either side of the Atlantic Ocean. Its range extends from the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

and North African coast to the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

and the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United S ...

. The depth range is between . Off Florida this urchin is usually found on algae or on broken coral substrates, particularly the rubble remains of dead ivory bush coral ('' Oculina varicosa''). It forms part of a species-rich community which includes other sea urchins,

mollusk 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 es ...

s, polychaete worms, crabs and encrusting organisms. These sea urchins are not usually found on living reefs, perhaps because there is seldom macro-algae growing there or because predatory fish hiding among the coral heads consume the juvenile sea urchins.

Biology

Examination of the contents of this urchin's stomach have shown that ''C. longispinus'' largely feeds on several species of red algae. At times of year when this is not available it probably eats small invertebrate

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

. In the laboratory they will feed on the seagrass '' Thalassia testudinum'' and may attack the starfish ''

Narcissia trigonaria ''Narcissia'' is a genus of echinoderms belonging to the family Ophidiasteridae. The species of this genus are found in Africa and America. Species: *''Narcissia ahearnae'' *''Narcissia canariensis'' *''Narcissia gracilis ''Narcissia'' is a ...

'' if hungry enough.

References

{{Taxonbar, from=Q2020012 Diadematidae Fauna of the Atlantic Ocean Fauna of the Mediterranean Sea Animals described in 1845 Taxa named by Rodolfo Amando Philippi