© 1984 by The Society for Integrative and Comparative Biology
Calcium Dynamics in Land Gastropods1
Formation et destruction des Tissus calcifiés, Université Parts VII 2, Place Jussieu, 75251 Paris Cédex 05, France
In land gastropods, calcium is precipitated in the shell, in connective calcium cells which are largely distributed through the whole connective tissue, in epithelial calcium cells of the digestive gland, and in the calcium gland cells of the skin and the mantle collar. Calcium is taken up from the external medium by food and by absorption through the sole skin. To adapt to terrestrial life, these animals have to eliminate appreciable amounts of calcium for their protection and their reproduction. During the egg laying period, a calcium flux occurs through the epithelium of the reproductive tract in order to supply the egg shell and the egg fluids. This egg calcium is taken up by the embryo. The maintenance of a positive calcium balance between its uptake and the loss is due to an important reservoir of easily mobilizable calcium in the form of calcium carbonate. This reservoir consists of the connective calcium cells which are constantly able to accumulate or release calcium as long as calcium is locally available or required. The epithelial calcium cells of the digestive gland are loaded with calcium phosphate; they are not a major calcium storage compartment, but have an essential function in detoxification. All of the calcium movement occurring across cell membranes and through epithelia concerns only calcium ions. All calcium movement can be regarded either as on-off systems or as reversible systems, both of which are certainly controlled by complex processes