Salt and Water Balance of the Spiny Lobster Panulirus Argus: the Role of the Gut

The rate of drinking of sea water averaged 1·5 ± 0·6 ml/kg body weight per 24 h and accounts for only a minor portion of the uptake of water required to balance estimated urine production. Imbibed water and ions, except Ca2+, are absorbed or diffuse across the gut wall into the haemolymph. The gut appears to be a route of net loss of Ca2+, derived from digestive juice and sea water, from the body. The gut does not appear to be a site of regulation of ionic levels in the haemolymph or a major site of water uptake.