INFLUENCE OF CARBONIC ANHYDRASE INHIBITORS ON SHELL GROWTH OF A FRESH-WATER SNAIL, PHYSA HETEROSTROPHA

¹ Department of Biology, Winthrop College, Rock Hill, S. C.

1. The rate of growth of Physa heterostropha may be controlled in the laboratory by using different modes of feeding.

2. Under the conditions of the experiments, growth rates for each feeding method, with the possible exception of that giving slowest growth, are constant over the range 3.00 to 5.99 mm. median shell lengths during two-day growth periods but are slower at both higher and lower lengths.

3. The drug 2-benzothiazolesulfonamide completely inhibits growth of the snail at concentrations about 1 mg. per liter. At 21° C. it is lethal at concentrations above this but appears to be somewhat less toxic at 26° C. Its effect is not due to the action of the drug as a carbonic anhydrase inhibitor but to an unknown side effect.

4. Diamox, benzenesulfanilamide, p-toluenesulfonamide and sulfanilamide, at the concentrations exhibiting maximum effect on growth, exhibit comparable degrees of inhibition of shell growth in snails fed for rapid growth.

5. Diamox at concentrations up to 1.5 mg. per liter does not decrease the growth rate of snails induced to grow slowly by the feeding method employed though this concentration inhibited growth to a significant degree in rapidly growing snails.

6. The results are consistent with the hypothesis that carbonic anhydrase is essential in rapid shell development of some molluscs but may be insignificant in slow growth induced by poor feeding conditions, and afford additional evidence that the enzyme is significant in mollusc shell formation.