Energy reserves and gonad steroid levels during the reproductive cycle of the Japanese mantis shrimp Oratosquilla oratoria De Haan, 1844 (Stomatopoda: Squillidae) in Pikou Bay, Dalian, China

This study aimed to characterize the seasonal cycles of energy storage and depletion in different organs of both sexes of the mantis shrimp Oratosquilla oratoria (De Haan, 1844). We sought to relate these findings to the reproductive cycle and environmental factors affecting such cycles and identify the link between steroid concentrations and the reproductive cycle. Individuals were collected monthly (May 2014 to April 2015) in Pikou Bay, Dalian, China, and the biochemical compositions of muscle, hepatopancreas, and gonads analyzed. Two peaks of protein levels were observed in the ovaries in May and November in accordance with the seasonal variations in gonadosomatic index (GSI). An increase in the lipid content of ovaries during gonad maturation was also observed. Protein levels in the hepatopancreas and muscle decreased before May and November in both sexes. Glycogen concentration in the muscle of females peaked in February and September, decreasing during the reproductive months. These subsequently decreased during the peaks in reproduction. In the hepatopancreas of male as well as in the ovaries, the largest reserves of glycogen were observed in the autumn and a subsequent decrease was seen during the transition from autumn to winter. These finding suggest that in O. oratoria both protein and lipids serve as energy reserves for reproduction. Besides, glycogen from either the ovaries or the hepatopancreas of males might be used during periods of intense activity and starvation. Two vertebrate sex steroids, 17 beta-estradiol and testosterone, were also identified in testes and ovaries, respectively, by means of ELISA. Fluctuating levels of these steroids during the reproductive cycle suggest they might be related to gonadal development in O. oratoria.