REGULATION OF STATOCONIA MINERALIZATION IN APLYSIA-CALIFORNICA IN-VITRO

Statoconia are calcium carbonate inclusions in the lumen of the gravit y-sensing organ, the statocyst, of Aplysia californica. The aim of the present study was to examine the role of carbonic anhydrase and ureas e in statoconia mineralization in vitro, The experiments were performe d using a previously described culture system (Pedrozo et al., J. Comp . Physiol. (A) 177:415-425). Inhibition of carbonic anhydrase by aceta zolamide decreased statoconia production and volume, while inhibition of urease by acetohydroxamic acid reduced total statoconia number, but had no affect on statoconia volume, Inhibition of carbonic anhydrase initially increased and then decreased the statocyst pH, whereas inhib ition of urease decreased statocyst pH at all times examined; simultan eous addition of both inhibitors also decreased pH. These effects were dose and time dependent. The results show that carbonic anhydrase and urease are required for statoconia formation and homeostasis, and for regulation of statocyst pH. This suggests that these two enzymes regu late mineralization at least partially through regulation of statocyst pH.