Osmoregulation in decapod crustaceans: implications to aquaculture productivity, methods for potential improvement and interactions with elevated ammonia exposure

Osmoregulation is an essential physiological process for the majority of aquatic crustaceans since it enables them to cope with the changes/discrepancies between the ion concentrations within their bodies and the aquatic environments they inhabit. With the exception of strict osmoconformers, crustaceans living in all aquatic environments continually regulate their hemolymph osmolytes and ultimately, the strategy and strength of this process dictate the diversity of habitats a crustacean can successfully occupy. While the degree of the osmoregulatory response is largely salinity dependent, the actual strength is highly species-specific. This has obvious and significant implications to the crustacean aquaculture industry, a multi-billion dollar industry that is continuously growing worldwide. Unfortunately, to date, a comprehensive review discussing the implications of this crucial process in crustaceans from an aquaculture perspective is lacking. Since crustacean aquaculture is almost exclusively based on large decapods, which also forms the main body of literature, they will therefore be the main focus of review. With basic background information on the regulatory mechanisms briefly described as a foundation for necessary knowledge, the implications of increased osmoregulatory demands to crustacean aquaculture is discussed extensively based on recent literature and research conducted in our laboratory. This includes the various factors that may influence osmoregulatory abilities, the causes leading to reduced productivity at sub-optimal salinities, potential methods that may broaden tolerable salinity ranges and how osmoregulation may interact with another important physiological process, i.e. ammonia excretion, which is crucial for cultured crustaceans. At the end of the review, future research directions are suggested to advance our understanding regarding this complex process that could substantially affect crustacean aquaculture productivity.