Respiration and osmotic behaviour of the copepod Acartia tonsa in diluted sea water

Abstract

1. 1. Adult females of the euryhaline planktonic copepod Acartia tonsa show increased oxygen requirements when the salinity of the surrounding sea water is lowered. 2. 2. The rise in respiration occurring during an 8-hr period of exposure to the diluted medium ranges from 0·077 μl oxygen/mg dry weight/hr at 90% sea water (0·7 per cent increase) to 16·061 μl oxygen/mg/hr at the lowest salinity 30% sea water (101·4 per cent increase). 3. 3. The increased metabolic rate can persist in diluted sea water for more than 24 hr. 4. 4. The internal osmotic concentration of copepods transferred from full-strength sea water 50% sea water falls rapidly due to entry of water into the body. After 1 hr no further osmotic change can be detected.