Paracentrotus Lividus: Characteristics, Habitat, Feeding, Reproduction

Paracentrotus lividus , popularly known as common hedgehog or purple hedgehog, is a very abundant species of hedgehog in the Mediterranean Sea and in the eastern part of the Atlantic Ocean, where it is generally found in crevices, openings or gaps in nearby rocks and corals. To the coast.

This species has a great gastronomic value, as it is considered a delicacy in France and Japan, where its gonads are part of dishes highly valued by many diners. This gastronomic interest implies, in turn, that it is a species of great interest to the fishing industry.

At the end of the 1970s, the populations of these urchins suffered a drastic decline, mainly caused by unregulated fishing off the French coast. However, at the end of the 90s, techniques and practices for the cultivation of this species in captivity were standardized, helping to satisfy market demands.

Paracentrotus lividus is considered by ecologists as a key species for the maintenance of the ecosystems where it lives, since it is a voracious herbivore and participates in the regulation of the growth and spread of algae in the waters near the coast.

Currently, in countries such as Spain, France and Ireland there are special laws and regulations for its fishing, in order to prevent the populations of the species from being negatively affected by intensive fishing.

General characteristics of Paracentrotus lividus

Paracentrotus lividus is a species of marine invertebrate that belongs to the group of echinoderms. Starfish, sea cucumbers, ophiuroids and other urchins also belong to this group; all characterized by an embryonic development where the anus is formed first and then the mouth.

– They have a body in the shape of a sphere or globe.

– They have pentaradial symmetry

– Its body is covered with long and pointed spines, except in the lower part, where the cavity of the mouth is located.

– They are considered “large” hedgehogs, as they measure between 7 and 8 cm in diameter.

– Despite being known as a purple hedgehog, it can be seen with a yellow, black, olive green, red coloration or with a combination of some of these colors.

– They generally live in numerous groups in the same place, since they have a common rearing of the larvae until they have changed to the final stage where they acquire the characteristic form of a hedgehog.

– It is believed that they live on average between 13 and 15 years, but some individuals of more than two decades of “age” have been observed.

Lifecycle

The life cycle of the purple hedgehog can be divided into at least 3 stages:

Larval stage

The union of the gametes produced by two individuals (fertilization) produces a typical planktonic larva of echinoderms known as “echinopluteus”. This is free-living, it can swim and feed on plankton.

Youth stage

During this stage the larva undergoes successive metamorphosis (changes in shape) until it is deposited on the seabed, where it adheres to a substrate. In this place begins a last metamorphosis, which ends with the typical shape of a hedgehog.

Adult stage

After the last metamorphosis, hedgehogs with a diameter of 1 cm are already sexually mature (they can reproduce), but they can continue to grow until they reach their maximum diameter (about 8 cm).

Habitat

The purple hedgehog ( Paracentrotus lividus ) generally lives in shallow water; It can be found on beaches and coasts, and even at a depth of 30 m in the sea. It generally colonizes hard substrates such as rocks, corals, pipes, ships, and submerged structures where it gets dark holes.

Sometimes it can be seen in puddles, camouflaged among algae, seashells or unoccupied (empty) shells. Hedgehogs have the peculiarity that they are always arranged horizontally, that is, with their mouths towards the ground, so that they can ingest algae and small invertebrates on the site.

Distribution

The purple hedgehog is found throughout the Mediterranean Sea and in the northeast Atlantic Ocean, starting from Scotland and Ireland, to southern Morocco and the Canary Islands. It is very common to find it in regions where, in winter, the water temperature ranges between 10 and 15ºC.

In summer it usually travels to the coasts of the western Mediterranean, in front of the coasts of Portugal and the Bay of Biscay. In the English Channel, a high fatality rate for sea urchins has been observed when temperatures are below 4ºC or above 29ºC.

Feeding

Most echinoderms are nocturnal, which means that they feed at night. Paracentrotus lividus travels several meters eating “sea grass”, sponge larvae, protozoa and diatoms, so it is said that they are omnivorous animals (that eat everything).

These hedgehogs can consume, in a single night, almost 30% of their body weight . When faced with low food conditions, these animals are able to slow down their metabolism (slow it down) to decrease their energy requirements.

Depending on the depth where they live, their diet can vary with respect to the species they find and the amount of food they eat. When food is scarce, these hedgehogs develop their digestive system to the maximum, so that they can assimilate as much food as possible when they eat.

Reproduction

This species of hedgehog has “separate sexes” (gonochoric) although it is not characterized by external sexual dimorphism (different male and female). In some cases hermaphroditic individuals have been found.

The fertilization of the sex cells (gametes) is external, that is, both parents expel their gametes to the sea, where they meet and become fertilized.

The sexual maturity of individuals varies mainly depending on environmental conditions. The temperature of the water and the availability of food are two of the most influential factors in the development of the gonads: at low temperatures and lack of food, sexual development is slower.

Furthermore, it has recently been observed that the photoperiod (the length of the day) also affects the development of the gonads; the photoperiod varies widely according to the seasons of each locality, for example:

– In some localities of Ireland the reproductive period of the purple hedgehog is between the months of May and June, while in other areas this occurs from March to July.

– In France the reproduction peak occurs between December and March, meanwhile in the west of France it is concentrated only in the month of March.

– In the region of Catalonia, Spain, the reproductive period runs from June to October in some places, but in others there are two periods, one from February to March and the other in August.

References

  1. Boudouresque, CF, & Verlaque, M. (2013). Paracentrotus lividus. In Developments in Aquaculture and Fisheries Science (Vol. 38, pp. 297-327). Elsevier.
  2. Zupo, V., Glaviano, F., Paolucci, M., Ruocco, N., Polese, G., Di Cosmo, A.,… & Mutalipassi, M. (2019). Roe enhancement of Paracentrotus lividus: Nutritional effects of fresh and formulated diets. Aquaculture nutrition , 25 (1), 26-38.
  3. Lemee, R., Boudouresque, CF, Gobert, J., Malestroit, P., Mari, X., Meinesz, A., … & Ruitton, S. (1996). Feeding behavior of Paracentrotus lividus in the presence of Caulerpa taxifolia introduced in the Mediterranean Sea. Oceanologica acta , 19 (3-4), 245-253.
  4. Boudouresque, CF, & Verlaque, M. (2001). Ecology of Paracentrotus lividus. Developments in aquaculture and fisheries science , 32 , 177-216.
  5. Boudouresque, CF, & Verlaque, M. (2013). Paracentrotus lividus. In Developments in Aquaculture and Fisheries Science (Vol. 38, pp. 297-327). Elsevier.

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