Meeting Abstract

P2.135  Sunday, Jan. 5 15:30  Functional Evidence for Neuroendocrine Regulation of Carbonic Anhydrase in the blue crab Callinectes sapidus MITCHELL, RT*; HENRY, RP; Auburn University rzm0015@auburn.edu

Cytoplasmic Carbonic anhydrase(CA) has long been known to be an essential component of osmoregulation in euryhaline crustaceans, including the green crab Carcinus maenas and the blue crab Callinectes sapidus. Recent evidence in C. maenas suggests that CA is under inhibitory control by a peptide hormone located in the x-organ sinus gland complex (XOSG). This hormone is released from the XOSG in animals acclimated to full-strength seawater, and is subsequently downregulated following low salinity acclimation, allowing for CA induction to support branchial ionic uptake. In this study we take the first steps in determining if a similar system is in place in C. sapidus. Crabs were treated with eyestalk ligation (ESL), which resulted in a 1.8-fold increase in CA activity in the posterior ion-regulating gills. This was accompanied by a 100-fold and 3-fold increase in cytoplasmic CA (CAc) and Na+/K+-ATPase expression, respectively. ESL failed to potentiate CA induction in crabs transferred from 35-15 ppt, however it did increase CAc mRNA by 5-fold. Injection of ESL crabs with eyestalk homogenate abolished the effects of ESL, suggesting that there is an endocrine substance in the C. sapidus eyestalk that inhibits CA activity and expression