Data from experiments measuring calcium uptake and acid-base flux in post-moult whiteleg shrimp (Penaeus vanamei) under different environmental calcium and salinity levels

A series of aquarium laboratory experiments lasting 3 months were conducted in April and September 2023 at the University of Exeter Aquatic Resources Centre on whiteleg shrimp (Penaeus vannamei) to understand how environmental concentrations of calcium, magnesium and salinity impact post-moult calcification. Penaeus vannamei collected from a commercial farm in St Andrews, Scotland in April and September 2023. Shrimp were held under laboratory conditions or 14 days prior to experiments seawater (temperature = 25.9°C; pH = 8.1-8.2; 14:10 h light:dark cycle). Two experiments were performed exposing shrimp (1-2 g wet mass) immediately after moulting to a range of environmental [Ca2+] levels (1.8-25 mmol/L, n = 27) at the same salinity of 20 ppt (experiment 1: Exeter_Uni_calcium_flux_experiments_Apr2023) or a range of salinities (1-25 ppt) with either varying or stable [Ca2+] levels (0.2-9.0 mmol/L; n = 56; experiment 2: Exeter_Uni_calcium_flux_experiments_Sep2023). For both experiments, whole-animal post-moult fluxes of calcium, total ammonia, and acid-base equivalents were measured in isolated flux chambers over a 24 hour period by determining changes in water concentrations of calcium, total ammonia and bicarbonate ions. Concentrations of these ions were determined by ion chromatography, auto-titration and colourimetric assay. Changes in concentrations of these ions in water over time were used to generate uptake rates of calcium and bicarbonate and excretion rates of total ammonia and net acid (in µEq/g/h) for the 0-2 hour period after moulting (in µEq/g/h) and cumulative uptake/excretion over the 24 hour post-moult period (in µEq/g). In experiment 2 only, exuvia (old exoskeletons) were collected immediately after moulting, weighed, dried and analysed for protein, chitin and mineral content by measuring mass loss after strong acid and base washing. The calcium content of exoskeleton mineral (Ca2+ and Mg2+) content in exoskeletons was measured by ion chromatography and presented as a proportion of total mineral divalent cation concentration.