Energy regulatory mechanisms underlying growth and reproduction in the Pacific oyster (Crassostrea gigas) revealed from an adipokinetic hormone perspective

As an important aquaculture bivalve, oyster growth, fattening, and reproduction all depend on efficient energy allocation. Glycogen is the major energy reserve in oysters, and its dynamic regulation directly affects growth performance, tissue condition, and reproductive investment. In this study, the Pacific oyster ( Crassostrea gigas ) was used as the model species to investigate the role of adipokinetic hormone (AKH), a neuropeptide functionally analogous to vertebrate glucagon, in the regulation of energy metabolism during growth and reproduction. The results showed that AKH was maintained at a low expression level during normal growth and was mainly involved in basal energy metabolism. In contrast, AKH was significantly upregulated during the transition of larvae from endogenous yolk nutrition to filter feeding, as well as under starvation stress, where it promoted glycogen mobilization to meet rapid energy demands. During reproduction, AKH exhibited stage-specific regulatory patterns: during gametogenesis, it was mainly involved in nutrient transport and the maintenance of protein and lipid metabolic homeostasis, whereas during spawning, it primarily mediated rapid glycogen breakdown to support intense energy release. These findings indicate that AKH -mediated carbohydrate metabolism is an important mechanism by which oysters coordinate energy allocation between growth and reproduction. This study not only reveals the endocrine basis of energy utilization in oysters, but also provides a new theoretical foundation for identifying molecular targets related to growth improvement, fattening regulation, and reproductive management in oyster aquaculture.