Population and gender-based differences in tissue-specific enzyme activities in brackish water and freshwater threespine sticklebacks, Gasterosteus aculeatus

Sticklebacks (Gasterosteus aculeatus) from a brackish water and a freshwater population were compared immediately after removal from their habitat and after being maintained in the laboratory. Glutamate dehydrogenase activities in the liver and both lactate dehydrogenase and aspartate aminotransferase activities in the axial muscle were higher in the brackish water sticklebacks than in the freshwater specimens. Liver glutamate dehydrogenase activities were higher in males than in females, whereas lactate dehydrogenase activities were distinctly higher in females. A significant positive correlation was found between size and both aspartate aminotransferase and lactate dehydrogenase. The population-specific activities of muscle enzymes are interpreted as an example of evolutionary adaptation of enzyme regulation. Received: 28 February 1997 / Accepted: 5 August 1997