| Paracentrotus lividus | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Echinoidea |
| Order: | Camarodonta |
| Family: | Parechinidae |
| Genus: | Paracentrotus |
| Species: | P. lividus |
| Binomial name | |
| Paracentrotus lividus | |
| Synonyms | |
| |
Paracentrotus lividus is a species of sea urchin in the family Parechinidae commonly known as the purple sea urchin. It is the type species of the genus and occurs in the Mediterranean Sea and eastern Atlantic Ocean. [1]
Paracentrotus lividus has a circular, flattened greenish test 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 are in groups of 5 or 6, arranged in small arcs. [2]
Paracentrotus lividus is found throughout the Mediterranean Sea and in the eastern Atlantic Ocean from western Scotland and Ireland to the Azores, Canary Islands and Morocco. It is most common in the western Mediterranean, the coasts of Portugal and the Bay of Biscay, where the water temperature in winter varies between 10 and 15 °C. [3]
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 meadows 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. 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. After exceptional quantities of rain fell in Corsica 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 outlets. There are wide swings in population densities over its range, which have not been completely explained. [3]
Individual P. lividus are either male or female although hermaphroditism has been observed. [3] They aggregate for spawning and release gametes into the water column. The larvae form part of the zooplankton for about 28 days before settling and undergoing metamorphosis. [3]
Paracentrotus lividus is a generalist browser, eating a range of red, green and brown algae in addition to seagrass. [4] 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 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 and Cystoseira and a much richer, three-dimensional community. The barren grounds can persist for years though whether this is due to overgrazing by urchins or prevention of recruitment of multicellular photosynthetic organisms by encrusting algae is unclear. [3]
Some juveniles of small fish species shelter among the spines. These include the clingfishes Apletodon incognitus and Lepadogaster candolii and the gobies, Gobius bucchichi , Zebrus zebrus and Millerigobius macrocephalus . [5]
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, Hexaplex trunculus . 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. [3]
The gonads are considered a delicacy in Lebanon, France, Italy, Spain, Malta, and parts of Croatia, most notably on the island of Korčula, and are also eaten to a lesser extent in Greece. The urchins have been harvested for export over a wider area including Croatia, Portugal and Ireland. [3]
Sea urchins or urchins are typically spiny, globular animals, echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal to 5,000 metres. Their tests are round and spiny, typically from 3 to 10 cm across. Sea urchins move slowly, crawling with their tube feet, and sometimes pushing themselves with their spines. They feed primarily on algae but also eat slow-moving or sessile animals. Their predators include sea otters, starfish, wolf eels, and triggerfish.
The diadema urchin or blue-black urchin is a species of tropical sea urchin, member of the Diadematidae family.
The orange-lined triggerfish is a demersal triggerfish. Although Balistapus is a monotypic genus, it is closely related to the genus Balistoides.
Kina is a sea urchin endemic to New Zealand. This echinoderm belongs to the family Echinometridae and it can reach a maximum diameter of 16–17 cm.
Astropyga radiata, the red urchin, fire urchin, false fire urchin or blue-spotted urchin, is a species of sea urchin in the family Diadematidae. It is a large species with long spines and is found in the tropical Indo-Pacific region. It was first described in 1778 by the German naturalist Nathaniel Gottfried Leske.
Lytechinus variegatus, commonly called the green sea urchin or the variegated sea urchin, is a species of sea urchin that can be found in the warm waters of the western Atlantic Ocean and Caribbean Sea.
Bald sea urchin disease is a bacterial disease known to affect several species of sea urchins in the Mediterranean Sea, North Atlantic and along the California coastline. Research suggests two pathogens are responsible for the disease, Listonella anguillarum and Aeromonas salmonicida.
Echinus is a genus of sea urchins. Sea urchins are echinoderms that are typically spherical or flattened with a covering of spine-like structures. Sea urchins tend to be important members of their ecosystems by grazing on other organisms and stabilizing populations. In addition to this, sea urchins play a large role in different economies globally as the urchin themselves and their roe are sold for consumption. The same is true for the species within the genus Echinus.
Heterocentrotus mamillatus, commonly known as the slate pencil urchin, red slate pencil urchin, or red pencil urchin, is a species of tropical sea urchin from the Indo-Pacific region.
Arbacia lixula, the black sea urchin, is a species of sea urchin from Europe.
Tripneustes ventricosus, commonly called the West Indian sea egg or white sea urchin, is a species of sea urchin. It is common in the Caribbean Sea, the Bahamas and Florida and may be found at depths of less than 10 metres (33 ft).
Cymodocea nodosa is a species of seagrass in the family Cymodoceaceae and is sometimes known as little Neptune grass. As a seagrass, it is restricted to growing underwater and is found in shallow parts of the Mediterranean Sea and certain adjoining areas of the Atlantic Ocean.
Psammechinus miliaris is a species of sea urchin in the family Parechinidae. It is sometimes known as the green sea urchin or shore sea urchin. It is found in shallow areas of the eastern Atlantic Ocean and the North Sea.
Sphaerechinus granularis is a species of sea urchin in the family Toxopneustidae, commonly known as the violet sea urchin, or sometimes the purple sea urchin. Its range includes the Mediterranean Sea and eastern Atlantic Ocean.
Sterechinus neumayeri, the Antarctic sea urchin, is a species of sea urchin in the family Echinidae. It is found living on the seabed in the waters around Antarctica. It has been used as a model organism in the fields of reproductive biology, embryology, ecology, physiology and toxicology.
Centrostephanus longispinus, the hatpin urchin, is a species of sea urchin in the family Diadematidae. There are two subspecies, Centrostephanus l. longispinus, found in the eastern Atlantic and Mediterranean Sea and Centrostephanus l. rubricingulus, found in the western Atlantic.
Diadema savignyi is a species of long-spined sea urchin belonging to the family Diadematidae. Common names include long-spined sea urchin, black longspine urchin and the banded diadem. It is native to the east coast of Africa, the Red Sea, the Indian Ocean and western Pacific Ocean. It was first described in 1829 by the French naturalist Jean Victoire Audouin. The specific epithet honours the French zoologist Marie Jules César Savigny who described many new marine species from the Mediterranean Sea and Red Sea. The type locality is Mauritius.
Diplodus vulgaris, the common two-banded sea bream, is a species of marine ray-finned fish belonging to the family Sparidae, which includes the seabreams and porgies. This species is found in the northeastern Atlantic Ocean and the Mediterranean. It is an important species for fisheries and is grown in aquaculture.
Gracilechinus acutus is a species of sea urchin in the family Echinidae, commonly known as the white sea urchin. It is an omnivore and feeds on algae and small invertebrates.
Apletodon dentatus, the small-headed clingfish, is a species of clingfish from the family Gobiesocidae. It is a benthic fish of shallow, rocky water on the coasts of the eastern Atlantic Ocean and the western Mediterranean Sea.