Sexual Reproduction in Pocillopora damicornis at High Latitude off South Africa

Abstract

Sexual reproduction in Pocillopora damicornis was studied off Durban in South Africa (29°S), close to its southernmost distribution in Africa. This was compared with P. damicornis reproduction on tropical reefs to ascertain how corals may adapt their reproduction on marginal reefs. Monthly gametogenesis was correlated with SST, light intensity, and day length. P. damicornis proved to be a hermaphroditic broadcast spawner in South Africa and had a higher fecundity than its tropical counterparts. However, its gamete development was slow (6-7 months) and confined to the warmer months of the year at this high latitude. Its reproductive pattern was similar to that found in this species in south Western Australia (32°S). Spawning in P. damicornis off South Africa occurred at the end of the summer and was inferred from the disappearance of mature gamete in April 2008. No correlation was found between monthly mean gamete diameter and light intensity or day length, but the increase in gamete size was correlated with a rise in SST, suggesting that this parameter regulates its spawning. The lower SST at high latitude may account for its extended gametogenesis and late spawning.