''Spatangus purpureus'', commonly known as the purple heart urchin, is a species 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) of ...

in the family

Spatangidae The Spatangidae are a family of heart urchin The heart urchins or Spatangoida are an order of sea urchins. Their body is a somewhat elongated oval in form, and is distinguished by the mouth being placed towards one end of the animal, and the ...

. It is found in the eastern Atlantic Ocean and the Mediterranean Sea, where it lives immersed in the sediment.

Description

''Spatangus purpureus'' has a somewhat flattened

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), ...

with a flat oral surface (underside) and a domed aboral surface (upper side). It is an irregular animal and not radially symmetric as are most sea urchins; there is a notch at the front and the mouth is forward pointing, while the anus is at the rear. It can grow to a length of and a width of . The test is reddish-purple and there are two types of spines, many short, silky, purplish spines up to long, and fewer beige

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

ous spines long.

Distribution and habitat

''Spatangus purpureus'' is native to the eastern Atlantic Ocean, 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 ea ...

and the

English Channel The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais) or ( Jèrriais), (Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Kana ...

. Its range extends from Iceland and the North Cape in Norway southwards to Senegal. It lives immersed in coarse sand or gravel, but seldom in mud. Its depth range is from the shallow sub-littoral, where it occurs in wave-sheltered areas, down to about .

Ecology

The diet of ''Spatangus purpureus'' is unknown, but it is often founds in beds of soft red algae. Analysis of the gonads show that they contain two polyunsaturated fatty acids that are present in the red algae as well as

palmitoleic acid Palmitoleic acid, or (9''Z'')-hexadec-9-enoic acid, is an omega-7 monounsaturated fatty acid (16:1n-7) with the formula CH3(CH2)5CH=CH(CH2)7COOH that is a common constituent of the glycerides of human adipose tissue. It is present in all tissues ...

, which is present in the sediment, the ratio varying with the relative abundance of these foods. These findings indicate that ''Spatangus purpureus'' has omnivorous feeding habits, with phytodetritus from the algal beds being an important part of the diet. This sea urchin is often associated with a small bivalve mollusc, '' Montacuta substriata'', which attaches to the spines. Another associate that lives among the spines is the polychaete worm '' Malmgreniella castanea'', some long, which has large purple scales. The red comb star ''

Astropecten aranciacus ''Astropecten aranciacus'', the red comb star, is a sea star of the family Astropectinidae. It is native to the east Atlantic Ocean (Portugal to Angola) and Mediterranean Sea. Habitat and behaviour ''Astropecten aranciacus'' lives very near the ...

'' is the main

predator 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 th ...

, and sea breams can crush the test and consume the contents. In the Mediterranean Sea, the helmet shell ''

Galeodea echinophora ''Galeodea echinophora'', the spiny bonnet or helmet shell, is a species of large sea snail, a marine gastropod mollusk in the family Cassidae, the helmet snails and bonnet snails. The fossil record of this species dates back from the Miocene t ...

'' drills a hole through the test and inserts its proboscis to digest the soft tissues inside.

References

{{Taxonbar, from=Q3018140 Spatangus Animals described in 1776 Fauna of the Atlantic Ocean Fauna of the Mediterranean Sea Taxa named by Otto Friedrich Müller