BRODIE, R.J.: Ontogenetic changes in rates of water loss and shell-wearing behaviors enable land hermit crab megalopae to avoid desiccating in air

The land hermit crab, Coenobita compressus , migrates from sea to land during the megalopal stage of postlarval development. As the megalopa emerges onto land, it encounters a physical environment wholly different from that of the sea. I investigated changes in C. compressus’ behavior and physiology that enable it to avoid desiccation on land. In one experiment, I examined changes in rates of water loss before, during, and after megalopae were able to settle on land to determine if their resistance to desiccation improved over time. I found that megalopae became increasingly resistant to desiccation with age. In the second experiment, I exposed megalopae with and without snail shells to relative humidities of 100, 92, 85, and 76 % to determine if the shell would increase survival in the lower humidity environments. Megalopae wearing shells were far more likely to survive the two lowest humidities compared to their naked counterparts. Thus, behavioral and morphological enhancements to desiccation resistance facilitate the land hermit crab’s transition to land.