The role of the adductor muscle as an energy storage organ in the pen shell Atrina japonica (Reeve, 1858)

Abstract

The biochemical composition and reproductive cycle of the pen shell Atrina japonica were investigated through separate analyses of the adductor muscle, gonad and the remaining tissues over a 1-year cycle. Seasonal variations in condition and gonadosomatic indices reflected those of gross weights of biochemical components of whole tissues. During the spring period, growth was initiated in the gonadal tissues simultaneously with the maximum weight gain in the adductor muscle, in which most of the energy reserves were stored, indicating that gametogenesis occurs at the expense of immediately ingested food energy. The increased energy reserves in the gonad during gametogenic development were exhausted completely during the summer spawning. Protein and carbohydrate reserves in the adductor muscle were used as catabolic substrates during spawning. The interannual shift in the timing of spawning appeared to be related to the changes in energy storage and gamete growth during the spring, probably reflecting changes in nutritional conditions in the ambient environment. Our results suggest that the adductor muscle of the pen shell plays a critical role as a major organ responsible for energy storage and that organ-specific biochemical composition can provide information of general relevance to the processes of energy gain and mobilization in bivalves.