Nutrient absorption and storage roles of hepatopancreas, gills, and muscles during moulting in Macrobrachium nipponense (Decapoda, Caridea, Palaemonidae): insights into phosphorus, calcium, and magnesium dynamics

Abstract Phosphorus, calcium, and magnesium are pivotal elements in the exoskeleton of crustaceans, playing a crucial role in the moulting stages. As crustaceans cannot synthesize these nutrients, their acquisition relies on external sources, with tissues such as the hepatopancreas and gills actively participating in this process. Studying changes in phosphorus, calcium, and magnesium concentrations in these tissues is essential for a comprehensive understanding of their role in nutrient absorption during the moulting stages. The hepatopancreas, gills, muscles, and carapace of Macrobrachium nipponense (De Haan, 1849) were taken from the premoult, postmoult, and intermoult stages to study the changes in phosphorus, calcium and magnesium contents in the hepatopancreas, gills, muscles, and carapace during the moulting process of M. nipponense . Three parallel experiments were measured in each stage, and 10-20 prawns were mixed for each stage. Phosphorus content per tissue unit weight was measured using the vanadium-molybdenum yellow colorimetric method, and calcium and magnesium content per unit weight of tissue were measured using atomic absorption spectrophotometry. Phosphorus in the hepatopancreas and gills increased significantly from the premoult stage to the postmoult stage ( ), and magnesium also showed the same trend. Calcium in the hepatopancreas was significantly highest in the premoult phase, whereas phosphorus was significantly highest in the postmoult stage ( ). The hepatopancreas Ca/P ratio decreased significantly before and after moulting, while it increased significantly in the gills ( ). The results show that the hepatopancreas and gills are the main tissues that absorb phosphorus, calcium, and magnesium. The hepatopancreas absorbs and stores calcium earlier than phosphorus. The changes in the Ca/P ratio of the hepatopancreas and gills found that M. nipponense consumes more phosphorus than calcium during moulting and growth, and the gills have a better ability to absorb calcium than phosphorus.