The activity of carbonic anhydrase in various tissues of fishes and other aquatic animals such as crustaceans and molluscs was measured by employing the CONWAY'S microdiffusion method for the determination of the rate of liberation of carbon dioxide produced from bicarbonate by the enzyme.
Within a single species of fish, the enzyme activity in blood varied remarkably, generally the activity is stronger in larger individuals than in smaller ones. The variation of the activity between individuals was found considerable also in liver and gill lamellae, yet non in pyloric caeca, stomach, kidney, and skeletal muscle. Among these tissues, blood was found to have the strongest activity and skeletal muscle the weakest, although the dark-colored muscle exhibited the activity as strong as visceral organs.
In crustaceans, cephalopods, gastropods and bivalves, the enzyme activity was strongest in gill and much weaker in blood (Table 2 b, c and d), on the contrary to the results of fishes. The enzyme activity in the mantle of cephalopods, gastropods and bivalves was generally stronger than in the arm or the foot, and this tendency was marked in decapods whose shells were well developed (Table 2 c and d).
The enzmy activity was also found in algae as well as in higher plant (Table 2 e).