THE PHYSIOLOGY OF THE ANTENNAL GLAND OF CARCINUS MAENAS (L.) IV. THE REABSORPTION OF AMINO ACIDS By R. BINNS

In previous work on antennal gland function in Crustacea the study of reabsorption of organic materials from the urine has been confined entirely to a consideration of carbohydrates, particularly glucose. For reviews of this earlier work, see Martin (1957) and Parry (i960). In Carcinus, as in other decapods, glucose is removed by active transport from urine passing through the antennal gland, though resorption is not always complete and there is a greater tendency for it to be eliminated from animals in dilute sea water (Binns, 1969c). Preliminary chromatographic analyses of blood and urine samples showed that amino acids are also reabsorbed from the urine when Carcinus is in normal sea water. When crabs were kept overnight in dilute media, it was found that blood amino acid concentrations were consistently greater than in animals in normal sea water, and also that relatively large amounts of amino acids were present in the urine. Therefore, simply by placing Carcinus in dilute sea water, the blood concentration of amino acids, as well as the rate of urine production (Binns, 19696; Nagel, 1934; Shaw, 1961), can be altered. These changes are of great interest, since simultaneous sampling of blood and urine from animals in dilute media will show how increases in blood amino acids, at high rates of urine flow, affect the reabsorption of these molecules after they are filtered into the antennal gland. Because Carcinus may live in dilute sea water in the field, it is important to know whether the antennal gland can conserve amino acids under conditions of stress which may be induced by changes in the concentration of the external environment of the animal.