MEPS 256:123-133 (2003)  -  doi:10.3354/meps256123

ABSTRACT: The effect of wave-induced disturbance on seasonal spawning patterns of the opportunistic polychaete Phragmatopoma lapidosa (Kinberg, 1867) was investigated by comparing seasonal fecundity, egg size and adult size between intertidal and subtidal worms at Boynton Beach, Florida. Fecundity patterns showed spawning peaks in summer and fall in both habitats, with reduced spawning in late fall and early winter. Subtidal females averaged 1015.2 eggs mm^-1 body length (range 0 to 2000 eggs mm^-1), while intertidal females averaged 607.4 eggs mm^-1 (range 0 to 1520 eggs mm^-1). Mean egg diameters were not significantly different between worms from the 2 habitats, ranging between 90.4 µm (SD = 3.7) and 89.5 µm (SD = 4.3) for intertidal and subtidal worms respectively. Inter- and intra-census comparisons of egg diameter, fecundity and adult length revealed few statistically significant relationships, suggesting that intertidal and subtidal worms were the same age. Adult lengths in both habitats did change seasonally. The smallest adult worms were found shortly after massive fall recruitment replaced a large percentage of individuals in both intertidal and subtidal populations. Stepwise multiple regression indicated that 76.2% of the variance in intertidal fecundity was explained by a negative correlation with wave height (40.4%), and a positive correlation with day length (34.7%). In contrast, 85.5% of the variance in subtidal fecundity was explained by a positive correlation with day length (77.4%), and a negative correlation with chlorophyll a concentration (8.1%). While habitat-specific differences in energy available for gametogenesis probably contribute towards the observed fecundity trends, the force of crashing waves could also influence fecundity, as it may affect frequency of spawning in intertidal but not subtidal habitats.

KEY WORDS: Phragmatopoma · Polychaetes · Fecundity · Spawning · Reproductive plasticity