Reproduction, larval occurrence and recruitment in Caribbean sea urchins

Populations of four species of sea urchins, Lytechinus variegatus, Tripneustes ventricosus, Echinometra viridis and Echinometra lucunter, exist in overlapping distributions on the shallow insular shelf of southwest Puerto Rico. Reproductive state, larval occurrence and recruitment patterns were measured over a 2-year period for each species. Laboratory-reared larvae were used to verify identification and measure larval period. The L. variegatus population has a broad, loosely synchronous reproductive season with the least gonad development in the spring. Individuals of T. ventricosus are also loosely synchronous with the resting phase probably occurring in the fall. In contrast, the Echinometra spp. both exhibited a very synchronous, short reproductive season which peaked in the fall when the water temperature was highest. The larvae of T. ventricosus require 4 weeks to reach metamorphosis, while the other three species take 2 weeks. Larvae of L. variegatus were present during most samplings; but, those of T. ventricosus were only present during one fall period. The larvae of the Echinometra spp. were present at the times expected from their reproductive periods. The pattern of seasonal recruitment closely parallels the reproductive season and time of maximum larval occurrence for only one species, L. variegatus. The pattern of larval occurrence and recruitment for T. ventricosus exhibits the least concurrence of the species examined. Indeed, T. ventricosus differed sharply from the others with respect to larval period as well. The lack of an association between larval occurrence and recruitment (as interpreted from size-frequency patterns) that was seen for the Echinometra spp. could result from contrasting patterns of post-settlement mortality and growth.