Influence of Oxygen Availability, Humidity and Salinity on Survival of Orthohalarachne Marine Mites Larvae: Limits to Dispersion

Orthohalarachne attenuata and O. diminuata mites are parasites of the respiratory system of pinnipeds. During hosts dives, mites are challenged to cope with changing conditions of available oxygen in the nasal cavity. Adults and nymphs live inside the host but larvae are active and responsible for colonizing new hosts. Hence, larvae are also exposed to environmental conditions with variable temperatures, dehydration or changes in salinity. In this study, we studied the effect of hypoxia, humidity and salinity on survival of mite larvae in O. attenuata and O. diminuata. We found that both species are highly tolerant to withstand long times under hypoxia. In turn, both species showed low survival when exposed to direct air. Finally, the hyperosmotic solution was highly harmful for O. attenuata compared to O. diminuata. Our results show that humidity rather than oxygen availability is a constraint for survival and a limitation for dispersal when searching for new hosts. The present study expands our knowledge of ecophysiology and adaptations to changing conditions experienced during the dispersal of these marine parasite species.