This study constitutes a first attempt to investigate intraspecific differences in osmoregulatory capacity and digestive and metabolic responses at the biochemical level in relation to hyper-and hypo-regulation in a single species of estuarine crab inhabiting contrasting habitats within a same intertidal area. We compared hemolymph osmolality, key digestive enzymes, glycemia and energy reserves in Neohelice granulata (Dana in Proc Acad Nat Sci Philadelphia 5:247-254, 1851) from the mudflat and saltmarsh of Mar Chiquita coastal lagoon (37°32 0 /37°45 0 S-57°19 0 /57°26 0 W) under a wide range of salinities (6-60 psu). Individuals from both sites exhibited high and similar osmoregulatory capacity, but while in individuals from mudflat low and high salinities affected lipase activity in hepatopancreas and triglycerides in muscle, in crabs from saltmarsh, high salinities affected glycogen in anterior gills. Low salinity differentially affected free glucose in anterior gills. The results suggest the occurrence of intraspecific distinct digestive and metabolic adjustments in relation to osmoregulatory responses and habitat.

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