Arbacia lixula

Long-spined sea urchin
Arbacia lixula from the Mediterranean
Scientific classification
Domain: Eukarya
Kingdom: Animalia
Phylum: Echinodermata
Class: Echinoidea
Order: Arbacioida
Family: Arbaciidae
Genus: Arbacia
Species: A lixula
Binomial name
Arbacia lixula
(Linnaeus, 1758)

The Black Sea Urchin, Arbacia lixula is a species of Sea Urchin from Europe.

Description

Test (shell) of a Arbacia lixula.

It is a medium-sized sea urchin, characterized by its deep black color and its haemispherical shape. All of its spines are roughly the same size (no "secondary spines"), and worn erected (never dishevelled when in the water). The anus on the top is surrounded by 4 plates forming an anal valve. The oral face is nearly naked, the mouth being surrounded by soft, dark-greenish skin.[1]

This species can be confused with the purple sea urchin Paracentrotus lividus, but the latter is never really black (though often very dark), has more dishevelled spines of many lengths, covers itself with debris, has spines around the mouth, no anal valve, and does not live exposed on the cliffs.

Habitat and geographical range

This species can be found on the coast of the Mediterranean Sea and Macaronesian Islands (Azores, Madeira, Canary Islands), and less commonly, on the Atlantic coast of Western Africa and the Brazilian coast. It is found typically at shallow waters, at depths from 0 to 30 m, in rocky shores. It has a good resistance to hydrodynamism due to a good attachment strength to rocks.

Biology

This species feeds mainly on crustose red algae and small filamentous algae. In a marine reserve in the Mediterranean, its population increased by a factor of over ten between 1983 and 1992, from eight individuals per square metre to a hundred individuals. It is thought that higher sea water temperatures favour this species. When it was excluded from an area of the reserve, the density of filamentous algae increased.[2]

References

  1. ↑ ZIEMSKI Frédéric, ANDRÉ Frédéric, in : DORIS, 15/5/2014 : Arbacia lixula (Linnaeus, 1758).
  2. ↑ Uthicke, Sven; Schaffelke, Britta; Byrne, Maria (2009). "A boom–bust phylum? Ecological and evolutionary consequences of density variations in echinoderms". Ecological monographs 79: 324. doi:10.1890/07-2136.1.

See also


This article is issued from Wikipedia - version of the Friday, October 16, 2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.