Interrelationships between water and metabolism in Artemia salina cysts: hydration-dehydration from the liquid and vapour phases.

Average weights of individual CaSO4-dried cysts (3 64/ig), shells (0-74 /ig) and embryos (2-90 /ig) of the brine shrimp, Artemia salina, were determined. ' Residual water' contents of these preparations were estimated to be 1-58 (cysta), 079 (shells), and 1-78 (embryos) in units of g HaO/ioo g dried weight. Cysts hydrated to a similar degree in the liquid or vapour phase of NaCl solutions at o °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/ioo g dried cysts.