SEXUAL REPRODUCTIVE EFFORT IN THE MEDITERRANEAN GORGONIAN PARAMURICEA-CLAVATA

Sexual reproductive effort in the Mediterranean gorgonian Paramuricea clavata was studied from 1990 to 1993 in a population dwelling at a depth of between 17 and 19 m off the Medes islands (northwestern Mediterranean). Variations in polyp fecundity with sex, polyp position within the colony, and colony size were studied, as was interannual variability. Onset of sexual maturity was on average delayed until colonies had attained a size of 20 (11 to 30) cm, i.e. an age of 13 (6 to 19) yr according to our estimates. Male and female colonies of P. clavata ripened synchronously and bore fertile polyps on nearly all branch orders. However, the percentage of fertile polyps and the number of gonads per fertile polyp decreased as branch order increased. Accordingly, reproductive effort was highest for polyps on first-order branches, which contributed 85% of the entire production of gametes. Reproductive effort increased exponentially with colony size due to increases in the percentages of fertile colonies and polyps and in the number of gonads per polyp, at least to a size of 35 cm in height. No significant interannual variation was detected over the 3 yr study period. The gorgonians present on a representative plot with a surface area of 1 m(2) produced, on average, 2 x 10(6) sperm sacs (9 g dry wt of male sex products) and 7 x 10(5) eggs (7 g dry wt of female sex products). Total reproductive effort was on the order of 9 g C m(-2) yr(-1).