Paracentrotus Lividus
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''Paracentrotus lividus'' 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), ...
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 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 ...
Parechinidae commonly known as the purple sea urchin. It is the
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
of the
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
and occurs in the Mediterranean Sea and eastern Atlantic Ocean.


Description

''Paracentrotus lividus'' has a circular, flattened greenish
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 diameter of up to seven centimetres. The test is densely clothed in long and sharply pointed spines that are usually purple but are occasionally other colours including dark brown, light brown and olive green. There are five or six pairs of pores on each ambulacral plate. The
tube feet Tube or tubes may refer to: * Tube (2003 film), ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM#Tubes, Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/e ...
are in groups of 5 or 6, arranged in small arcs.Purple sea urchin - ''Paracentrotus lividus''
Marine Life Information Network. Retrieved 2011-08-23.
Paracentrotus lividus Banyuls.jpg, Aboral side Paracentrotus lividus, oral view.JPG, Oral side (underside, with the mouth at the center) Paracentrotus lividus spines.JPG, Close-up on the spines, showing a lighter circle at the root EchinoideaSeeigel02.JPG, Brown young Paracentrotus lividus MHNT France.jpg,
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) ...


Distribution

''Paracentrotus lividus'' is found throughout 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 in the eastern
Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
from western
Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...
and
Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...
to the
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,
Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...
and
Morocco Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...
. It is most common in the western Mediterranean, the coasts of
Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
and the
Bay of Biscay The Bay of Biscay ( ) is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Point Penmarc'h to the Spanish border, and along the northern coast of Spain, extending westward ...
, where the water temperature in winter varies between 10 and 15 °C.


Habitat

''Paracentrotus lividus'' is usually found just below low water mark at depths down to twenty metres and sometimes also in rock pools. It is found on rocks and boulders, and in
seagrass meadow A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...
s of '' Zostera marina'' and '' Posidonia oceanica''. Although '' Cymodocea nodosa'' is a preferred food item, it is seldom found in meadows of this seagrass, perhaps because the shifting sand substrate does not suit it or because of pressure from
predators 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 feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
. In fact it avoids soft substrates and can sometimes be found clustered on stones or shell "islands" surrounded by sand. In shallow or exposed waters it can use its mouth and spines to dig into soft rocks to create cavities into which it returns and in which it exactly fits. Where the urchins are numerous, the rock may be honeycombed by these excavations. Smaller individuals particularly use these retreats, which provide some protection from predators. In lagoons and rock pools, individuals are smaller than they are in the open sea. ''P. lividus'' is unable to tolerate low
salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...
. After exceptional quantities of rain fell in
Corsica Corsica ( , , ; ; ) is an island in the Mediterranean Sea and one of the Regions of France, 18 regions of France. It is the List of islands in the Mediterranean#By area, fourth-largest island in the Mediterranean and lies southeast of the Metro ...
in the autumn of 1993, there was mass mortality of urchins in the Urbini Lagoon. However, the urchin is relatively unaffected by organic pollution and heavy metals. In fact, it flourishes near
sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewerage, sewer system. Sewage consists of wastewater discharged fro ...
outlets. There are wide swings in population densities over its range, which have not been completely explained.


Biology

Individual ''P. lividus'' are either male or female although hermaphroditism has been observed. They aggregate for
spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...
and release
gamete A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...
s into the
water column The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical ( pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined ...
. The larvae form part of the
zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...
for about 28 days before settling and undergoing metamorphosis.


Ecology

''Paracentrotus lividus'' is a generalist browser, eating a range of red, green and brown algae in addition to seagrass. The benthic community is much affected by the number of urchins and their food preferences. Where they are numerous they tend to be surrounded by "barren ground" colonised by encrusting
Corallinaceae The Corallinaceae are one of the two extant Coralline families of red algae; they are differentiated from the morphologically similar Sporolithaceae by their formation of grouped sporangial chambers, clustered into sori. The Corallinoideae ...
species and characterised by a low biomass of primary producers with a small number of associated species. Where numbers are low, there tend to be forests of ''
Laminaria ''Laminaria'' is a genus of brown algae, brown seaweed in the order Kelp, Laminariales (kelp), comprising 31 species native to the north Atlantic and northern Pacific Oceans. This economically important genus is characterized by long, leathery L ...
'' and '' Cystoseira'' and a much richer, three-dimensional community. The barren grounds can persist for years though whether this is due to
overgrazing Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, game reserves, or nature ...
by urchins or prevention of recruitment of multicellular photosynthetic organisms by encrusting algae is unclear. Some juveniles of small fish species shelter among the spines. These include the clingfishes '' Apletodon incognitus'' and '' Lepadogaster candolii'' and the
gobies Gobiidae or gobies is a family of bony fish in the order Gobiiformes, one of the largest fish families comprising over 2,000 species in more than 200 genera. Most of gobiid fish are relatively small, typically less than in length, and the fam ...
, '' Gobius bucchichi'', '' Zebrus zebrus'' and '' Millerigobius macrocephalus''. The main predators on ''P. lividus'' in the Mediterranean Sea are the spider crab ('' Maja crispata''), the fish '' Diplodus sargus'', '' Diplodus vulgaris'', '' Labrus merula'' and '' Coris julis'' and the
gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...
, ''
Hexaplex trunculus ''Hexaplex trunculus'' (previously known as ''Murex trunculus'', ''Phyllonotus trunculus'', or the banded dye-murex) is a medium-sized sea snail, a marine gastropod mollusk in the family Muricidae, the murex shells or rock snails. It is inclu ...
''. The spiny starfish ('' Marthasterias glacialis'') is a main predator elsewhere. Predation is dependent on size; juvenile urchins are more vulnerable as their spines are less formidable. In most locations the urchins are nocturnal feeders, but where predators are more active at night the urchins may feed during day instead.


Use as food

The gonads are considered a delicacy in Lebanon, France, Italy, Spain, Malta, and parts of Croatia, most notably on the island of
Korčula Korčula () is a Croatian island in the Adriatic Sea. It has an area of , is long and on average wide, and lies just off the Dalmatian coast. Its 15,522 inhabitants (2011) make it the second most populous Adriatic island after Krk. The populat ...
, and are also eaten to a lesser extent in Greece and Tunisia. The urchins have been harvested for export over a wider area including Croatia, Portugal and Ireland. Additonally, sea urchin meat has been popularised in modern cuisine as "Uni", with paracentrotus lividus being known as "Murasaki Uni". It is primarily harvested in Hokkaido, Japan alongside its counterpart "Bafun Uni".https://hokkaidouni.com/blogs/uni/exploring-the-world-of-sea-urchins-types-gender-and-seasonality


References


External links

* {{Taxonbar, from=Q901067 Parechinidae Edible shellfish Echinoderms of the Atlantic Ocean Fauna of the Mediterranean Sea Echinoderms described in 1816 Taxa named by Jean-Baptiste Lamarck Sea urchins as food