Physico-chemical characterisation of the extrapallial fluid of a common <span style="font-size:14.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";color:black;mso-ansi-language:EN-IN; mso-fareast-language:EN-IN;mso-bidi-language:HI" lang="EN-IN">tellinid <span style="font-size:14.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:HiddenHorzOCR;color:black;mso-ansi-language:EN-IN; mso-fareast-language:EN-IN;mso-bidi-language:HI" lang="EN-IN">bivalve <i>Macoma b</i><i><span style="font-size:14.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";color:black;mso-ansi-language:EN-IN; mso-fareast-language:EN-IN;mso-bidi-language:HI" lang="EN-IN">irmanica </span></i><span style="font-size:14.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";color:black;mso-ansi-language:EN-IN; mso-fareast-language:EN-IN;mso-bidi-language:HI" lang="EN-IN">(Philippi) in the mudflats of Sundarbans mangrove, Bay of Bengal</span></span></span>

Abstract

The chemical composition of the extrapallial fluid of <i>Macoma birmanica </i>was examined in order to understand the process of calcification. Concentrations of inorganic ions Na⁺, K⁺, Ca²⁺, cl^- and SO₄^2-were found in higher proportion in the pallial fluid than those in the ambient medium. Calcification from pallial fluid was found to be related to the removal of proton from the fluid through the excretion of NH₃. The concentration of total positive charge is 14.1 % higher than that of negative charge, indicating the presence of non-difusible negative ions. From EPR measurements, apparent complexation capacity of Mn in the fluid was in the order of 0.37 × 10^-5<i>M </i>and forms 1:1 chelate with stability constant of 1.1 × 10⁴per mole. It was found to be highly undersaturated with respect to the solubility of skeletal aragonite in the pallial fluid and has

<span style="font-size:14.0pt;line-height:115%;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";color:black;mso-ansi-language:en-in;="" mso-fareast-language:en-in;mso-bidi-language:hi"="" lang="EN-IN">the capacity to keep high concentration of calcium in solution through the formation of ion pair with HCO₃^-_. Precipitation of aragonite was initiated through the formation of Ca <span style="font-size:14.0pt;line-height:115%;font-family:" times="" new="" roman";="" mso-fareast-font-family:hiddenhorzocr;color:black;mso-ansi-language:en-in;="" mso-fareast-language:en-in;mso-bidi-language:hi"="" lang="EN-IN">chelates.</span></span>