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Gonadal maturation independent of photic conditions in laboratory reared sea urchins pseudocentrotus depressus and hemicentrotus pulcherrimus

, : Gonadal maturation independent of photic conditions in laboratory reared sea urchins pseudocentrotus depressus and hemicentrotus pulcherrimus. Zoological Science (Tokyo) 5(5): 979-988

The gametogenesis in two species of the laboratory-reared sea urchins, Pseudocentrotus depressus and Hemicentrotus pulcherrimus, were compared under different artificial photic conditions. Juvenile sea urchins derived from zygotes of the same batch were reared under constant illumination at C until they were transferred to experimental environments, where they were kept for about a year. The experimental environments were: continuous light at constant temperature ( C) (20 LL); continuous light at ambient temperatures (Amb LL); continuous darkness at ambient temperatures (Amb DD); changing photoperiod in phase with ambient daily photoperiod at C (In-phase); changing photoperiod 6 months out of phase with ambient daily photoperiod at C (Out-of-phase); and ambient light at ambient temperatures (Control). The stages in gametogenesis were determined according to a histological standard. In P. depressus, the gonads in the ambient temperature groups (Amb DD, Control) matured simultaneously; the gonads in the constant temperature groups (20 LL, In-phase, Out-of-phase) also became ripe at the same time, but earlier than those in ambient temperature groups (Amb LL was lost by an accident). In H. pulcherrimus, the gonads in ambient temperature groups (Amb LL, Amb DD, Control) ripened simultaneously; but in the groups kept at C (20 LL, In-phase, Out-of-phase), the gonads remained very immature. These results indicate that in the two species no specific photic conditions are required for gametogenesis to proceed. The results in H. pulcherrimus also suggest the presence of a critical temperature to permit the progression of gametogenesis.


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