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Summary
This paper presents the first study of the life history of a Brazilian reef coral, with reference to Siderastrea stellata. Fecundity and growth rate were determined for four colony size classes collected from the Itacolomis Reefs, Brazil (16°53.816′S; 039° 04.965′W). Colony size-frequency distribution was analyzed to evaluate the potential for maintenance, growth and recovery of the population. The fecundity of size class 1 (up to 2.5 cm in diameter or 5 cm2) was significantly lower than that of the other three classes, which did not differ among themselves (averaging 8 oocytes/polyp). Colonies with less than 1.8 cm in diameter (or 2.5 cm2) did not have gametes. The number of mature polyps tended to increase with colony size: some polyps of class 2 (2.5 < x ≤7.9 cm diameter) colonies did not have oocytes, while polyps from classes 3 (7.9 < x ≤ 12.6 cm diameter) and 4 (× >12.6 cm diameter) were always fertile. The linear extension was similar among the four size classes, being around 2.5 mm per year, corresponding to an annual increase of 5 mm in colony diameter. The first gametes occurred in the third year, with planulation occurring during the fourth year of life. Colony size-frequency distribution showed the presence of many size classes, as would be expected on undisturbed reefs. Class 2 colonies were the most abundant; the largest colony was 486 cm2 (or 25cm diameter), i.e. possibly 50 years old. Ten percent of colonies were within size class 1 (recruits) and 90% were sexually mature. The early onset of reproduction, brooding of larvae, intermediate size (average colony size at the studied site was 62 cm2, or 9 cm diameter), and massive corallum may be advantageous in the habitat preferentially occupied by S. stellata, namely, the reef top and horizontal substrates in shallow waters <10 m deep. The presence of large colonies, characterized by lower mortality rate, larger reproductive output and greater longevity, also indicates a low probability of population extinction. Disturbances that decrease colony sizes to less than 20 cm2 (or 5 cm in diameter), corresponding to a 10 years old colony, may sharply reduce the population's prospects of survival, since below this size, maximum fecundity has yet to be attained.