Reproduction of sea urchin Loxechinus albus in Chiloé Island, Chile

During 1986-1989, the seasonal maturation and gonad index (gonad weight/body weight × 100) of adult Loxechinus albus were examined at nine sites, and the appearance of four-armed echinopluteus larvae was investigated at three sites off the eastern coast of Chiloé Island, Chile. Spawning occurred during November-January when the gonad indices fell to a minimum, the number of mature specimens decreased and four-armed larvae appeared, corresponding to the rise in water temperature. The number of four-armed larvae appearing at the northern site was markedly less than that at the southern site. The sea urchins matured in January and February immediately after spawning at many sites and a high percentage of maturation lasted for a long period at some sites. These findings are considered to be associated with high food availability and annual narrow ranges of water temperature.