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Adaptation de la faune souterraine aux basses températures : mécanismes et enjeux écologiques

Abstract : Subterranean fauna adaptations to low temperatures: mechanisms and ecological aspects.
Subterranean ecosystems are generally characterised by reduced yearly thermal variations (± 1°C along the year). Thus, hypogean organisms should present stenotherm profiles (reduced tolerance to thermal variations), as they never endure variation of the temperature during their life cycle. Yet, several biospeologists observed a surprising survival to negatives temperatures in the subterranean crustacean Niphargus rhenorhodanensis. In order to determine the N.
rhenorhodanensis thermobiological scale as well as the adaptive mechanisms allowing its cold tolerance, we measured its responses to low temperatures and we compared them to those of another hypogean crustacean (Niphargus virei) and to those of a morphologically close surface-dwelling crustacean (Gammarus fossarum). N. rhenorhodanensis showed larger survival times at -2°C than the two other organisms.
Performance experiments (oxygen consumption, locomotory and ventilatory activities) when exposed to different temperatures (from
-2 to 28°C) pointed out that N. rhenorhodanensis exhibited a eurytherm profile (maximising its performance on a broader range of temperature). Finally, during cold exposure, N. rhenorhodanensis shows i) a cryoprotectant (trehalose, free amino acid) body accumulations, ii) a decrease in free water body content (water that is able to participate in ice formation), and iii) a inoculative freezing tolerance. At the opposite, inoculative freezing is lethal in the two other organisms, with limited cryoprotectant body content increases, and no variation in free water body contents. With the support of recent phylogeographical studies, we hypothesise that cold hardiness pointed out in N. rhenorhodanensis might result form its life history during quaternary glaciations.
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Submitted on : Wednesday, September 19, 2007 - 4:33:50 PM
Last modification on : Wednesday, November 20, 2019 - 2:42:03 AM
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  • HAL Id : tel-00173375, version 1



Julien Issartel. Adaptation de la faune souterraine aux basses températures : mécanismes et enjeux écologiques. Ecologie, Environnement. Université Claude Bernard - Lyon I, 2007. Français. ⟨tel-00173375⟩



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