Reproduction, dispersal and settlement of the bathyal ophiuroid Ophiocten gracilis in the NE Atlantic Ocean

Ophiocten gracilis is an ophiuroid found at bathyal depths in the North Atl antic Ocean. The adults show strong seasonal reproduction, with an ophioplu teus in the surface plankton. Settling postlarvae were collected in sedimen t traps moored at 1000 and 1400 m depth in the NE Atlantic during Julian Da ys 142 to 212 (May to July) in 1996. During this period, growth of postlarv ae in the traps was linear and the diet consisted of phytodetritus and fora minifera. Experiments suggest that postlarvae sink at rates of up to 500 m d(-1), although this may well be slower in the natural environment. The hig h fecundity, seasonality and high population density resulted in high ferti lization success, and many of the offspring were advected outside the norma l adult range, where they were able to settle but did not survive to adulth ood.