This study documents the annual reproductive cycle of the sea urchin Echinometra mathaei on the South coast of Iran in Persian Gulf, Bostaneh, from April 2006 through May 2007. At each sampling date, one gonad from each urchin was selected for histological assessment and after the removal of one gonad, the remaining four were dried to a constant weight for determination of gonad index. Sea urchins from E. mathaei populations had shown an annual gametogenic cycle, the timing of which was temporally and spatially consistent. The histology of the gonads revealed six different maturity stages grouped in three main reproductive phases: recovering and growing, premature and mature, partly spawned and spent. Male urchins had mature gametes for a longer period than females, possibly an adaptive strategy that increases the probability of fertilization. Premature and maturing stages occurred from late winter to early summer. Spawning occurred during early summer to late summer. Recovering urchins were observed from late summer to early winter. Gonad indices showed a peak in weight from late winter to late-spring (3.72 ± 2.3 for females; 4.25 ± 2.5 for males; Mean ± SE) then a decline for both sexes. There was a peak in the proportion of spawning from late winter to early summer that correlated with the observed peaks in gonad indices and gametogenic cycles. The demographic implications of this reproductive pattern are that new recruits can enter the population through synchronous spawning during the breeding period and smaller haphazard spawning events at other times of the year and reproduction is seasonal and cycle mediated by seawater temperature, day length and feeding activity.

Keywords