Relationship between energy allocation and gametogenesis in Aulacomya atra (Bivalvia: Mytilidae) in a sub-Antarctic environment

Gametogenesis and temporal variation in energy allocation to different organs were analyzed in Aulacomya atra from the Beagle Channel (Tierra del Fuego, Argentina). Our results show that A. atra presents an extended spawning period from late winter to spring when the lowest value of mantle-gonad index (MGI) and maximum number of spawned individuals were observed. The MGI in mature males increased as the energy density of the mantle-gonad (ED_MG) decreased, indicating an increase in mass of lower energy values. In contrast, the MGI in mature females increased as ED_MG increased, indicating an increase in mass of higher energy values. Consequently, males and females reached a similar energy content of the mantle-gonad (EC_MG) by means of different strategies: males have gonads of larger size but with lower energy by unit of mass than females. Besides, we observed a decrease in the digestive gland index (DGI) in concordance with an increase in the MGI of mature individuals, and a trend towards the depletion of ED and EC in the digestive gland during gonadal maturation. Our results evidence the role of the digestive gland as an energy reservoir and a different energy allocation strategy between sexes during gonadal maturation.