Gametes and embryos of sea urchins (Paracentrotus lividus, Lmk., 1816) reared in confined conditions: their use in toxicity bioassays

Sea urchins of the species Paracentrotus lividus, collected along the Southern Adriatic coast at the end of their reproductive season, were reared in a recirculating aquarium under controlled temperature and feeding conditions in order to induce off-season maturation of gametes to be used in toxicity bioassays. After 14 weeks of rearing, the gonad index was calculated, histological analyses of the gonads were performed, their fertilisation ability was measured and the EC50 for copper in embryotoxicity bioassays was evaluated. The sperm motility pattern (based on the percentages of total motile and rapid sperm, together with sperm velocity parameters) was assessed using a computerised analyser. All specimens showed a significant increase in gonad yield with respect to field-collected animals and were in pre-spawning or spawning stages. The motility parameters, fertilisation ability and EC50 level of the collected gametes were comparable to those of field-matured specimens. In conclusion, the sea urchins reared under experimental conditions were characterised by faster gonad maturation than the field population, producing viable gametes and larvae whose biological response in toxicity bioassays was similar to that of field-reared specimens of P. lividus.