ABSTRACT
Lice from pinnipeds – sea lions, seals and walruses – are the only insects capable of surviving marine dives. Throughout their evolutionary history, they have adapted to tolerate hypoxia, high salinity, low temperature and, in particular, to tolerate conditions of high hydrostatic pressure. To understand the limits of the capacity of lice to survive during host deep dives, we conducted a series of controlled experiments in the laboratory. We collected lice from elephant seals and submitted the different life stages to high pressure conditions. Lice were first exposed to one of four hydrostatic pressures: 30, 80, 150 or 200 kg cm−2. They were then exposed a second time to higher or lower hydrostatic pressure conditions to test for the impact of the first experience, which could either be deleterious or trigger physiological adaption, allowing them a better tolerance to high pressure. We found that lice from elephant seals can tolerate hydrostatic pressures higher than 200 kg cm−2 (close to 200 atm), which is equivalent to 2000 m depth. Adults exhibited lower recovery times than nymphs after immersion at high hydrostatic pressure. Our findings show that lice have developed unique adaptations to endure extreme marine conditions. We discuss these extreme performances in relation to the morphological characteristics and physiological responses to diving in these insects.
Footnotes
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: M.S.L., J.E.C., C.R.L.; Methodology: M.S.L., J.E.C., F.A.S., R.B.V., J.C.R.; Formal analysis: J.E.C., C.R.L.; Investigation: M.S.L., F.A.S., R.B.V., J.C.R.; Data curation: J.E.C.; Writing - original draft: M.S.L., J.E.C., C.R.L.; Writing - review & editing: M.S.L., J.E.C., C.R.L.; Supervision: M.S.L., C.R.L.; Funding acquisition: M.S.L.
Funding
This research was funded by the Agencia Nacional de Promoción de la Investigación, el Desarrollo Tecnológico y la Innovación (PICT 2015-0082 and PICT 2018-0537) and the Lerner-Grey Fund for Marine Research.
Data availability
The rough data and the R script are available from Mendeley: http://dx.doi.org/10.17632/zm4c4y4yz5.1
- Received April 15, 2020.
- Accepted July 14, 2020.
- © 2020. Published by The Company of Biologists Ltd
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