SEXUAL REPRODUCTION AND COLONY GROWTH IN THE SCLERACTINIAN CORALPORITES ASTREOIDES

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Abstract
This study examines patterns of sexual reproduction and colony growth for Porites astreoides Lamarck, an abundant Caribbean reef coral. Five factors influence the reproductive condition of this coral in Jamaica: (i) Season, (ii) lunar day, (iii) polyp location within a colony, (iv) colony size, and (v) colony age. P. astreoides has an unusual mixed breeding system: Approximately half of colonies are hermaphroditic and half are female. Although gonads occur in some colonies throughout the year, there are clear seasonal differences both in the number of reproductive colonies within the population and in colony fecundity. Male gametes are spawned monthly around the time of the full moon. The abundance and maturity of brooded larvae peaks prior to the new moon. Within reproductive colonies, gonads and brooded larvae are more abundant in central polyps than at colony edges. Among female colonies, the onset of reproduction is apparently related to colony size, whereas the fecundity of individual polyps is related to colony age. Hermaphroditic and female colonies differ in the size at which most colonies are reproductive. Rates of vertical and lateral growth for P. astreoides increase with colony size, but not with colony age. These findings demonstrate how the combined effects of several variables can cause individuals within a population to differ greatly in reproductive condition, fecundity, and growth rate.