Brackish and amphibious mangrove environments represent potential entrance portals for evolutionary transitions from marine to limnic and terrestrial life styles. Euryhaline and semiterrestrial mangrove-inhabiting crabs may therefore be considered as models for transitional stages occurring during invasions of freshwater and land. Sesarma curacaoense may be a prime example. It is considered as the closest extant relative of an ancestor that gave rise to an adaptive radiation of fully limnic and terrestrial crabs on the island of Jamaica. In contrast to most other mangrove-inhabiting crab species, where only the adults are physiologically adapted to non-marine conditions (larval export strategy), it shows conspicuous life-history adaptations, including the production of few but large and yolk-rich eggs, an abbreviated and partially food-independent larval development, strong larval capabilities of osmoregulation, and limited planktonic dispersal (retention strategy). Similar reproductive and developmental adaptations, although more pronounced, have recently been discovered also in some of the closely related endemic Jamaican species of freshwater and land crabs. This suggests that life-history studies in mangrove crabs that follow a retention strategy, but not in those exporting their larvae toward the sea, may aid to the understanding of evolutionary pathways and transitional steps occurring in invasions of non-marine environments.