Effects of reduced salinities on metamorphosis of a freshwater-tolerant sesarmid crab, Armases roberti: Is upstream migration in the megalopa stage constrained by increasing osmotic stress?

This strong physiological adaptability enables the megalopa of A. roberti to cross during its upstream migration, within a short time (6 days), strong osmotic gradients, so that metamorphosis is possible also in freshwater habitats where the conspecific adult crabs live. The speed of migration appears to be limited by physiological constraints related to changes in the capability for osmoregulation occurring during the course of the moulting cycle.