Samples of the scleractinian coral Agaricia agaricites (Limaeus) were studied for time of planula release, planula production and related characteristics. The corals were collected over a 2 yr period on the fringing reef of Curaqao at depths from 5 to 30 m. Two distinct reproductive pattems emerged. Based on these patterns and on consistent differences in skeletal morphology, such as size of calices and n b b e r of septa, the separation of the form A. agaricites humilis Vemll as a distinct species, A. hurnilis, from the other forms of A. agaricites is proposed. A. humilisplanulated throughout the year. A. agaricites shed planulae in spring and summer, a period of increasing sea water temperatures. In A, humilis 78 % of the colonies (N = 133) released planulae within 1 wk after collection, compared with only 26 % ( N = 91) in A. agaricites. Maxlmum diameter of the smallest planulating colonies of A. humilis was about 4 times less (28 mm) than in A. agaricites (108 mm). Planula production per unit living tissue area was 4 times larger (0.86 planulae cm-2 wk-') in A. humilis than in A. agaricites (0.23 planulae cm-2 wk-l). However, planula volume was 5 times lower (0.166 mm3) than in A. agaricites (0.860 mm3). It appears that A. humilis employs an opportunistic reproductive strategy compared with A. agaricites. A. humilis is mainly confined to the shallow reef flat and drop off zone (5 to 12 m) and colony diameters rarely exceed 100 mm. A. agaricitesreaches its greatest abundance on the deeper reef slope (10 to 30 m), growing to a maximum size of 600 mm. The differences in reproductive strategies can be explained in relation to the predictability of their habitats.

This study reports maximum linear extension rates of several species of stony corals (Scleractinia) during formation of the colony base. Growth was determined during the first years after settlement of larvae on artificial substrata. Diameters of juveniles at the start of growth intervals ranged from 1.4 to 28.2 mm; in 66 % of measurements they were < 10mm. Substrata were deployed in different orientations between 5 and 3 0 m depth and thus offered a large range of environmental circumstances to demonstrate potential growth. A total of 769 growth values 2 0 . 6 mm mo-' diameter extension rate was measured in juveniles of 13 species. In 8 species sufficient data were collected to estimate maximum growth rates. Maximum diameter extension rates of about 2.1 to 2.4 mm mo-' were found in 1 ahermatypic species and in 6 hermatypic species. Acropora sp. was one of the latter species, which is remarkable in view of its relatively high adult growth rate. A range of 2.1 to 2.4 mm mo-' points to much slower juvenile growth rates than previously assumed, but is not much different from the scarce growth data available in the literature. The ahermatypic species Madracis pharensis forma pharensis showed a maximum diameter extension rate of 11.6mm mo-'. This rate is comparable to the most rapid linear extension rates ever recorded in hermatypic corals. It demonstrates for the first time that such fast linear skeletal extension rates are possible in the absence of zooxanthellae, not only on the actual growth site, but also in other colony regions. This finding constitutes an enigma, considering contemporary knowledge of calcification mechanisms and coral growth.

Juvenile coral colonies (diameter C50 mm) of Agaricia humilisand A. agaricjtes (Scleractinia) were studied through time in their natural habitat between 5 and 23 m depth on the fringing reef of C u r a~a o (Netherlands Antilles, Caribbean). At 6 censuses (in 1 yr), data were collected on status, morphology and size of juveniles to investigate the following aspects of life histories: frequency of disturbance and mortality, nature of disturbing factors, frequency of fission and fusion processes, and growth during the 5 intervals, as well as annual growth. Absolute linear growth was not dependent on colony size. Maximum linear growth (diameter increase, 80 pm d-l, was potentially equal in both Agaricia species and independent of depth. However, different disturbance levels, related to depth, resulted in a significant difference in actual annual growth in relation to depth zones. A difference in species-specific coral morphology caused a different level of disturbance in the 2 species. In addition there was a negative relation between coral size and mortality in A. humilisjuveniles. Dynamic aspects of the life histories of A. humilis and A. agaricites integrate well with depth-related differences in relative abundance and with differences in reproductive characteristics of the species.

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