Salinity does not affect late-stage in-egg embryonic, or immediate post-hatch development in an ecologically important land crab species

Environmental drivers such as salinity can impact the timing, and duration of developmental events in aquatic early life stages of crustaceans, including terrestrial crabs of the family Gecarcinidae. Low salinity delays larval development in land crabs, but nothing is known about its influence on the crucial late-stage encapsulated embryonic, or immediate post-hatch development. Therefore, we exposed fertilised late-stage embryos of the Christmas Island red crab (Gecarcoidea natalis) to differing salinities (100, 75, 50, or 25 % sea water) for 24 h during their spawning period and measured some key developmental and physiological traits. We found no effect of salinity on time of first heartbeat, time of hatching, first in-egg embryonic and post-hatching heart rate (bpm), or post-hatch activity duration (h). These results highlight the importance of considering all early life stages when fully characterising the effects of environmental drivers on crustacean development, including under climate change.