Hypo-osmotic regulation coupled with reduced metabolic urea in the dogfish Poroderma africanum: An analysis of serum osmolarity, chloride, and urea

摘要: “Pyjama sharks” (Poroderma africanum) were exposed to a wide range of salinities, over which blood serum was analysed for osmolarity, chloride and urea concentrations. Fish divided into two groups, those fed twice weekly (high intake), once month (low intake). Both groups the same salinity range. “High intake” fish showed characteristic elasmobranch osmolarity picture, with values slightly hyper-osmotic at all times. “Low fish, however, degree hypo-osmotic regulation. Serum both overlapped very low salinities. also affected by diet, so that again distinct sets produced, overlap lower When previously well-fed starved period one month, decreased simultaneously. Consequently, it is felt directly related levels. not found be showing change in when salinity. It shown, reduction food intake, more than fortnight, can reduce metabolic extent depressing and, hence, shift ionic osmotic equilibrium between sea water. This may result varying degrees hypoosmotic