Gametogenesis and gonad mass cycles in the common circumpolar Antarctic echinoid Sterechinus neumayeri

Polar conditions (low and stable seawater temperature coupled with highly seasonal primary productivity) constrain reproduction in benthic invertebrates. The reproductive cycle of the common Antarctic sea urchin Sterechinus neumayeri was investigated at monthly intervals over a 2 yr period in relation to seasonality of chlorophyll standing stock and ability to feed. Competence to spawn increased gradually throughout the austral winter to peaks in September to November. Gonad mass varied strongly, both seasonally and among 3 geographically close sites. Spawning occurred between October and January at each site, and was strongest in November of both years. Spawning was not always accompanied by a reduction in gonad mass because of simultaneous feeding and deposition of nutritive tissue for the forthcoming winter. Spawning was annual but there was also strong evidence for longer, multi-year periodicity in reproductive output. Histological analysis indicated an 18 to 24 mo vitellogenic cycle, with oocytes developing from 20 to 50 μm in the first winter, and from 50 to 120 μm in the second winter. Of total oocyte volume increase (vitellogenesis), 93% occurred within the last 12 mo. Spermatogenesis took 12 mo. S. neumayeri does not feed during the austral winter, and vitellogenesis is therefore predominantly decoupled from energy intake. Much of the cost of reproductive synthesis is met at a time of severe energy limitation.