Variability in reproductive mode and larval development within the Capitella capitata species complex

A comparative analysis was carried out of reproductive mode, larval develop ment pattern, and larval growth rate under identical conditions of three me mbers of the Capitella capitata species complex: Capitella sp I from New Yo rk, US, Capitella sp M from shallow hydrothermal vents off Milos, Greece, a nd Capitella sp S from an intertidal flat on Sylt, Germany. In addition, th ree populations from salmon farms, Capitella K (Kilmelford, Scotland), Capi tella Cm and Capitella Ct (Cranford, Ireland), are described for the first time. Three development patterns were observed: planktotrophic (Capitella K and Ct populations), lecithotrophic (Capitella spp I, M and Cm populations ), and direct development (Capitella sp S). Experiments with planktotrophic larvae from the Capitella K population at different temperatures, in the p resence and absence of light and with several kinds of substrate were not s uccessful in inducing settlement, although differences in the duration of l arval survival were observed. Overall, major differences in reproductive mo des and larval development patterns were observed among representatives of different species and populations reared under identical culture conditions . In contrast, such modes and patterns are consistent across generations. W hereas larval type and developmental mode appear to be determined largely b y genetic factors, environmental conditions have an important influence on the timing of key developmental processes, such as settling and growth.