DISCRETE SEASONAL REPRODUCTION IN AN ABYSSAL PERACARID CRUSTACEAN

Oocyte growth within the ovary and the developmental stage of embryos in the marsupium were studied in time-series material of the cumacean Leucon profundus Hansen, 1920 from 2900 m depth in the Rockall Trough, northeast Atlantic. Vitellogenic oocyte stages were present between April and October, with early vitellogenesis in April-June giving way to late vitellogenesis in July-September. No data were available for the period November-January, but newly-produced broods were present in the marsupium from February to April, indicating oviposition (and presumably mating) early in the year. Release of young occurred during late spring and early summer, after an inferred brooding period of about 14 months. Both vitellogenic oocyte growth and release of young therefore coincided with the seasonal peak of phytodetrital flux to the seabed in this region. a generation time for females of L. profundus of at least 3 years is inferred, with a delay of 3 years between successive broods if females in this species are iteroparous. The prolonged (>12 months) retention of broods suggests that previous studies, noting simply the year-round occurrence of brooding females im populations, may have failed to recognize sharply seasonal breeding patterns in other deep-sea peracarid species.