Growth model of the reared sea urchin Paracentrotus ... - SciViews

General introduction
During the day, they stay near the roots of the plants, away from predators.
At night, they climb to the top of the fronds and feed on their softest parts
(Nedelec et al, 1981).
Like almost all echinoids, P. lividus is gonochoristic and fertilization is
external. When animals are ripe in early spring (Allain, 1975; Spirlet et al,
1998a) and in some localities in autumn (Crapp & Willis, 1975;
Fernandez, 1996), spawning is synchronized and triggered by an external
signal, e.g., temperature change or disturbance (Spirlet et al, 1998a;
Spirlet, 1999).
Figure 2. Paracentrotus lividus. A. Echinopluteus. B. Postlava a few days after
metamorphosis.
Homolecithal eggs are fertilized in the water column and develop into
free-swimming planktotrophic larva characteristic of echinoids: an
echinopluteus (Fig. 2A). This larva develops 4, 6 and then 8 arms
supported by calcareous skeletal rods. After a few weeks, the
echinopluteus will develop a rudiment inside the wall of an epidermic
invagination (the vestibule) located on the right-hand side of the body
(Strathmann, 1978). When the larva becomes competent, it seeks a solid
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