In this experimental study, we compared the
embryonic respiration rate in air and water of six East
African sesarmid species with intertidal, supratidal and
arboreal habits, to highlight possible adaptations in
embryonic metabolism to their different lifestyles. The
embryos of all analysed crabs showed bimodal respiration,
but we did not find a trend towards an enhanced embryonic
oxygen uptake in air from the intertidal to the arboreal and
supratidal species. However, the late-stage embryos of the
most land-adapted species, Chiromantes spp., showed an
enhanced metabolism when immersed in sea water that we
interpreted as an adaptive recovery mechanism to cope
with the storage of by-products due to marine-based metabolic pathways during long emersion periods. Thus, we
showed that the embryos of land-adapted species, although
still strongly water dependent, are well adapted to semiterrestrial habitats and represent a minor limiting factor for
females, which are not restricted in their emersion period
by the oxygen requirements of their embryos.