Meeting Abstract

P1.48  Jan. 4  CARBONIC ANHYDRASE IN INVERTEBRATE SHELL MATRIX HORNE, F.R.; Texas State University, San Marcos FH01@txstate.edu

The freshwater mussels, snails and crustaceans all form a highly calcified shell in waters where neutral pHs and low calcium concentrations are common. Epithelial cells of the mantle or hypodermis secrete an organic matrix of protein and polysaccharides along with minerals extracellularly. Macromolecules serve as sites of ion concentration, crystal nucleation, crystal growth, and control of crystal morphology. Crustaceans manufacture and calcify a new shell in a matter of several days during molt, whereas mollusks show a much slower accretionary shell growth. Calcium ions are pumped from the environment into body fluids and then out again at the site of mineral deposition along with bicarbonate to maintain electrical neutrality. In shell calcification the calcium and carbonate ion product must exceed its solubility product to sustain crystal growth. In association with carbonate ions two issues arise: a) availability of an adequate supply of bicarbonate ions to provide carbonate ions, and b) there must be a means to remove protons. Dehydration and hydration of carbon dioxide is a rather slow reaction without the enzyme carbonic anhydrase (CA). An extracellular CA might solve the first dilemma. The second issue might be solved by CA and/or extracellular urease. In this study cuticles were decalcified with formic acid, sectioned and treated with antibodies to bovine RBC CA II and jack bean urease. Using CA antibodies the CA appears to be localized through out the cuticle matrix of Scyllarides latus and the shell matrix of Quadrula quadrula. Non-calcified lobster tissues and controls did not react with antibodies and did not seem to have CA. Extracellular CA may function along with intracellular CA in maintaining bicarbonate levels and/or removing protons in both crustaceans and mussels.