The Role of the Antennal Gland in the Osmotic and Ionic Regulation of Carcinus Maenas*

Abstract
Several previous studies on various littoral and semi-terrestrial crabs [Carcinus maenas—Nagel (1934), Webb (1940); Pachygrapsus crassipes—Prosser, Green & Chow (1955), Gross (1959), Gross & Marshall (1960); Uca pugnax and U.pugiator— Green, Harsch, Barr & Prosser (1959)] have pointed out the effective role of the antennal gland in regulating the ionic concentration of the urine in sea water of various concentrations. Recently, Flemister (1958) and Green et al. (1959) have suggested that in certain of the more terrestrial crabs (Uca spp. and Gecarcinus lateralis) water may be reabsorbed from the urine. Riegel (unpublished) has obtained direct evidence of the withdrawal of water from the urine of Hemigrapsus nudus. As will be shown here, specimens of Carcinus maenas are also capable of withdrawing water from their urine in 100% sea water or in water-saturated air. In addition, specimens of C. maenas can also alter the urine/blood (hereafter designated U/B) ratios of sodium, magnesium, chloride, osmotic pressure and possibly calcium.