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

sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

in the family

Spatangidae The Spatangidae are a family of heart urchins. There are three recognised genera within the family; '' Granopatagus'', '' Plethotaenia'', and ''Spatangus ''Spatangus'' is a genus of heart urchins in the Spatangidae family.Hansson, H. (2009)Sp ...

. 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 (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...

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 east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

and the

English Channel The English Channel, also known as the Channel, is an arm of the Atlantic Ocean that separates Southern England from northern France. It links to the southern part of the North Sea by the Strait of Dover at its northeastern end. It is the busi ...

. 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. It is a rare component of fats. It is a common constituent of the glycerides of human adipose tis ...

, 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 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 ma ...

'' Malmgreniella castanea'', some long, which has large purple scales. The red comb star '' Astropecten aranciacus'' is the main

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

, and sea breams can crush the test and consume the contents. In the Mediterranean Sea, the helmet shell '' Galeodea echinophora'' drills a hole through the test and inserts its proboscis to digest the soft tissues inside.

References

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