Interrelationships Between Water and Metabolism in Artemia Salina Cysts: Hydration-Dehydration from the Liquid and Vapour Phases

Abstract

Average weights of individual CaSO₄-dried cysts (3.64 µg), shells (0.74 µg) and embryos (2.90 µg) of the brine shrimp, Artemia salina, were determined. ‘Residual water’ contents of these preparations were estimated to be 1.58 (cysts), 0.79 (shells), and 1.78 (embryos) in units of g H₂O/100 g dried weight. Cysts hydrated to a similar degree in the liquid or vapour phase of NaCl solutions at 0 °C. Sorption isotherms revealed marked hysteresis for isolated shells, but not for entire cysts or the embryonic component. Adsorption data were plotted according to the Brunauer-Emmett-Teller equation and BET parameters were calculated and discussed. Cyst populations incubated at relative vapour pressures of water of 0.96 and above underwent a loss of dried weight, emerged in the hygrostats, and showed a decrease in viability. The foregoing did not occur at relative vapour pressures of 0.925 and below. The water content required for initiation of these events was estimated to be somewhere in the range of 46 to 72 g H₂O/100 g dried cysts.