Stone sea urchin
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Stone sea urchin ( Paracentrotus lividus ) |
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| ( Lamarck , 1816) |
The stone sea urchin ( Paracentrotus lividus ) is a sea urchin found in the Mediterranean and Eastern Atlantic .
features
The stone sea urchin has a housing diameter of up to 7 cm. The housing is always flattened anteriorly and rarely dorsally. The numerous very pointed spines are up to 3 cm long and are very variable in color. The color ranges from dark purple to brownish to green. The ambulacral plates have 5 pairs of pores from which a corresponding number of ambulacral feet protrude, which have suction cups on the top. The gonads are golden yellow in males and bright red in females.
ecology
nutrition
The stone sea urchin is basically a herbivore and feeds primarily on algae and plants. The following species are listed as preferred food sources: The red alga Rissoella verruculosa , the brown algae Cystoseira amentacea , Padina pavonica and Undaria pinnatifida . The seaweed tang grass ( Cymodocea nodosa ) and neptune grass ( Posidonia oceanica ) are also among the main sources of food. All parts of the plant are consumed by the Neptune grass: living leaves with and without epiphytic growth, dead leaves, rhizomes and roots. However, the composition of the food spectrum changes greatly with the age and size of the animals. Analyzes of the intestinal contents as well as in vitro observations showed, however, that the stone sea urchin is a generalist that can also feed on sponges (Porifera), hydrozoans (Hydrozoa) or copepods (Copepoda). With extremely high population densities, cannibalism can also occur. In the Mediterranean, the stone sea urchin feeds mainly at night. In the Irish saltwater lake Lough Hyne , however, the sea urchin is diurnal, which is interpreted as an adaptation to the feeding pressure by the nocturnal ice star ( Marthasterias glacialis ).
Masking
With the help of the suction cups on the ambulacral feet, the stone sea urchin often masks its aboral side with leaves of the Neptune grass ( Posidonia oceanica ), algae, empty mussel shells, small stones or plastic particles. Smaller individuals camouflage themselves more often than larger ones. Several hypotheses exist for this behavior. On the one hand, the masking should protect against light, ultraviolet radiation and predation. On the other hand, the masking like an umbrella protects the apical openings of the ambulacral system (madrepore plate) from clogging by blown sand.
Predators
The most common sea bream ( Diplodus sargus ), two-banded bream ( Diplodus vulgaris ), brown wrasse ( Labrus merula ) and mermaid ( Coris julis ) are among the most common predators in the Mediterranean . The spider crab Maja crispata and the blunt prickly snail ( Hexaplex trunculus ) are also frequent predators. The ice star ( Marthasterias glacialis ) is also given as a predator. However, due to its low abundance, this only plays a subordinate role in the Mediterranean. In the Atlantic the situation is different, where starfish (Asteroidea) and crustaceans (Crustacea) play a major role. In addition to the mentioned spiny also in the literature Crab ( Cancer pagurus ), the velvet crab ( Necora puber ), the crab Maja brachydactyla and the Common beach crab ( Carcinus maenas ) cited.
Reproduction
Stone sea urchins are separately sexed, although hermaphroditism has also been observed. In vitro, sexual maturity begins at months of age and 13 to 20 mm in diameter. The spawning season is highly dependent on the region and habitat, but occurs in spring and / or autumn. The spawning season runs from May to July on the western Irish coast, but from April to May and September to October on the Côte d'Azur . During the spawning season, 10 to 20 individuals gather on striking stones or the leaf tips of the Neptune grass ( Posidonia oceanica ) at dusk and release their gametes at the same time. The widespread assumption that spawning occurs on full moon nights could not be observed.
Occurrence
The distribution area covers the entire Mediterranean and the northeast Atlantic from Scotland and Ireland to southern Morocco and the Canary Islands including the Azores . The stone sea urchin is particularly common in regions where the water temperature is between 10 and 15 degrees Celsius in winter and between 18 and 25 degrees Celsius in summer. This is the case in the western Mediterranean, on the coasts of Portugal and in the Bay of Biscay . The northern and southern limits of the distribution area correspond to the 8 degree isotherm in winter and the 28 degree isotherm in summer.
habitat
The stone sea urchin is a typical species of the sublittoral and occurs at depths of up to 20 meters. Individual individuals have also been observed at a depth of 80 meters. However, this species is much more common in the upper water layers. Also tidepools serve as habitat. Rock soils and seagrass meadows consisting of Neptune grass ( Posidonia oceanica ) or common seaweed ( Zostera marina ) are populated. The stone sea urchin is absent from kelp grass ( Cymodocea nodosa ) stocks , although this is one of its preferred food sources. This is attributed either to a higher predation rate or to the sandy soil between the shoots, which is unsuitable for locomotion. The stone sea urchin generally avoids soft soils and groups itself there on individual rocks or large shells. With the help of its teeth, the stone sea urchin is able to drill caves into the substrate (such as sandstone , limestone , granite , basalt , but not hard slate ). These cup-shaped indentations protect the sea urchins from predators but also from being torn away by waves and are permanently or temporarily inhabited. Sometimes these caves are so close together that the substrate has a honeycomb structure.
Chemical parameters
The optimal salinity is between 15-20 and 39-40. The stone sea urchin reacts sensitively to changes in the salt content. For example, unusually heavy rainfall (450 mm in 48 h) in autumn 1993 over the Etang d'Urbino lagoon , Corsica , led to a mass extinction of the stone sea urchin, as the salinity sank to 7. High concentrations of heavy metals are tolerated, whereby these, with restricted growth, are accumulated. Petroleum pollution results in a 100% mortality rate in tidal pools. After the Erika tank accident it took 3 years for the stone sea urchin population to regain its original density. Organic pollution, such as that caused by urban sewage, promotes the growth of the stone sea urchin. For example, high population densities were measured in the heavily polluted Rade de Brest , the Étang de Berre and the wastewater discharges from Rabat and Marseille .
Use by humans
The stone sea urchin gonads are considered a delicacy in the Mediterranean and are eaten raw. Consumption is mainly in Spain and France , and to a lesser extent in Italy and Greece . For export, the stone sea urchin is or was also harvested in Ireland , Croatia and Portugal .
literature
- John M. Lawrence: Edible Sea Urchins: Biology and Ecology . Elsevier 2006. pp. 243-275.
- Enric Sala, Mikel Zabala (1996): Fish predation and the structure of the sea urchin Paracentrotus lividus populations in the NW Mediterranean . Marine Ecology Progress Series 140, pp. 71-81.
swell
- ↑ Rupert Riedl: Fauna and flora of the Mediterranean . Edited by Smoky Riedl, Barbara Schweder. Unchanged reprint of the 1983 edition. Seifert, Vienna 2011, ISBN 978-3-902406-60-6 , p. 601 .
- ↑ a b c Helmut Göthel: Lower Animals Color Atlas Mediterranean Fauna: Lower Animals and Fish. Ulmer, Stuttgart 1997, ISBN 3-8001-7368-9 . P. 213
- ↑ Lawrence, John: Sea Urchins: Biology and Ecology . Pp. 250-260
- ↑ Lawrence, John: Sea Urchins: Biology and Ecology . P. 255
- ↑ Lawrence, John: Sea Urchins: Biology and Ecology . Pp. 266-267
- ↑ Lawrence, John: Sea Urchins: Biology and Ecology . Pp. 270-275
- ^ A b c Lawrence, John: Sea Urchins: Biology and Ecology . Pp. 243-244
- ↑ Lawrence, John: Sea Urchins: Biology and Ecology . P. 243.
