Shell repair rates and carbonic anhydrase activity during shell repair in Helisoma duryi (Mollusca)

Abstract

Mantle tissue carbonic anhydrase titres were found to vary with shell deposition rates. Following shell injury at the growing edge, linear shell deposition rates and mantle tissue carbonic anhydrase specific activity were found to increase significantly. Increased mantle enzyme activity was detected for a period of 10 days following injury. Replacement of shell in the region of excision was found to occur on a plane slightly lower than that of the surrounding normal shell. This requires the establishment of a new growing edge so a single plane of deposition may be restored. This suggests that the process of shell regeneration does not only include the patching of the actual injury but also allows for the establishment of a new growing edge to correct for the displacement of the plane of shell deposition. These two components of the shell regeneration process have been designated phases I and II, respectively. A third phase allows for the thickening of the mineralized layers of the newly deposited shell. Localization of elevated carbonic anhydrase activity in the portion of the mantle directly underlying the shell injury suggests that a regulatory system is present which enables the animal to detect, define, and localize shell injury repair, expediting the process.