Reference: Blol Bull., 153: 369-376. (October, 1977) CALCIUM STORAGE AND DISTRIBUTION IN THE DIGESTIVE GLAND OF BENSON I A MONTICOLA (GASTROPODA : PULMONATA) : A HiSTOPHYSIOLOGICAL STUDY A. SEN GUPTA 1 Department of Zoology, Punjab University, Chandigarh 160014, India The pulmonate digestive gland is so well-mined an area of investigation that the reasons for another study on it seem to rest on shaky ground. The structure of this organ has been well known for over eighty years now ; it consists of numerous tubules (acini) surrounding the intestine and separated from one another by interacinar spaces. The acini are constructed of an epithelium of various cell types, and a long, as ytt unresolved, controversy has raged over whether there are three kinds or four. Even here, much is to be said in favor of the view of Abolins-Krogis (1970) that all types except calcium cells are different functional manifestations of one basic type. Whatever be the ultimate answer to that, it is undisputed that one of the cell types is the calcium cell. It is also uncontested that in addition to serving the function of digestion, this organ in gastropods serves for calcium storage as well (Manigault, 1939; Abolins-Krogis, 1961). An ex-tensive body of literature (e.g., Abolins-Krogis, 1968; Saleuddin, Miranda, Losada and Wilbur, 1970) attests that this organ also releases calcium and other sub-stances in times of increased demand, such as during shell regeneration. The release of calcium is mediated by the breakdown of calcium spherites within the calcium cells (Abolins-Krogis, 1961). While the enormous contribution of this author to knowledge of these spherites is beyond question, much still remains un-known regarding them. Wilbur ( 1972, p. 108) states that "the spherites, con-sisting of both mineral and organic components, merit further attention as calcifying systems." It may be mentioned here that these spherites are also of interest by reason of being intracellular calcifying systems, in contrast to shell and bone. The present communication attempts to elucidate the mechanism of calcium uptake, storage and distribution by this gland. In sum total the amount of calcium taken up by the mollusc is always greater than that lost in normal physiological processes such as shell formation and excretion, and also its level in the blood is maintained within narrow limits (Greenaway, 1971 ). This points to some sort of regulatory mechanism. Some exceedingly simple hypotheses have been put forth to account for the observed constancy of blood calcium, such as precipitation during periods of saturation in the blood and solubilization in times of depletion. How-ever, matters may not be as simple as that, and the present work proposes a specialized cellular process that may be capable of finer regulation. MATERIAL AND METHODS Specimens of Bensonia nwnticola (Gastropoda: Pulmonata) were collected from the hills surrounding Solan (Himachal Pradesh, India) during the months 1 Present address: Department of Biophysics, Panjab University, Chandigarh 160014, India. 369
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