Seasonal variability in gonad development in the sea urchin (Paracentrotus lividus) on the Basque coast (southeastern Bay of Biscay).

The main limiting factor to carrying out toxicological bioassays with sea urchin larvae is the restricted period for the availability of viable gametes. Although studies have been undertaken of the reproductive cycle of the sea urchin for several areas of the Bay of Biscay, only limited information exists for the southeasternmost area (the Basque coast). Furthermore, this geographical zone presents some particular environmental conditions, e.g., relatively warm waters. In this study, the gonad state of a population of Paracentrotus lividus, settled on the rocky shores of the city of Donostia-San Sebastian have been monitored. These sea urchins are observed to behave like a typical Atlantic population, with generally high gonad indices and a single yearly main spawning period, between April and May. Further, females show a shorter spawning period than males, becoming the limiting organisms for the availability of larvae.
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