Why do ants differ in acclimatory ability? Biophysical mechanisms behind cuticular hydrocarbon acclimation across species

Journal of Experimental Biology, vol. 225

Abstract

Maintaining water balance is vital for terrestrial organisms. Insects protect themselves against desiccation via cuticular hydrocarbons (CHCs). CHC layers are complex mixtures of solid and liquid hydrocarbons, with a surprisingly diverse composition across species. This variation may translate into differential phase behaviour, and hence varying waterproofing capacity. This is especially relevant when temperatures change, which requires acclimatory CHC changes to maintain waterproofing. Nevertheless, the physical consequences of CHC variation are still little understood. We studied acclimatory responses and their consequences for CHC composition, phase behaviour and drought survival in three congeneric ant species. Colony sub-groups were kept under cool, warm and fluctuating temperature regimes. Lasius niger and Lasius platythorax, both of which are rich in methyl-branched alkanes, showed largely predictable acclimatory changes of the CHC profile. In both species, warm acclimation increased drought resistance. Warm acclimation increased the proportion of solid compounds in L. niger but not in L. platythorax. In both species, the CHC layer formed a liquid matrix of constantly low viscosity, which contained highly viscous and solid parts. This phase heterogeneity may be adaptive, increasing robustness to temperature fluctuations. In Lasius brunneus, which is rich in unsaturated hydrocarbons, acclimatory CHC changes were less predictable, and warm acclimation did not enhance drought survival. The CHC layer was more homogeneous, but matrix viscosity changed with acclimation. We showed that ant species use different physical mechanisms to enhance waterproofing during acclimation. Hence, the ability to acclimate, and thus climatic niche breadth, may strongly depend on species-specific CHC profile.

Authors 5

1. Lucas Baumgart Aachen Institute of Biology II

   Centre National de la Recherche Scientifique · Université Sorbonne Nouvelle · Johannes Gutenberg University Mainz · Laboratoire Matière et Systèmes Complexes · RWTH Aachen University

   Affiliation as printed

   Institute of Biology II, RWTH Aachen University 2 , Worringerweg 2, 52074 Aachen , Germany

   Institute of Organismic and Molecular Evolution (iomE), Johannes Gutenberg-University Mainz 1 , Hanns-Dieter-Hüsch-Weg 15, 55128 Mainz , Germany

   Matière et Systèmes Complexes (MSC), UMR CNRS 7057, Université de Paris 3 , 75205 Paris Cedex 13 , France

2. Marti Wittke

   Johannes Gutenberg University Mainz

   Affiliation as printed

   Institute of Organismic and Molecular Evolution (iomE), Johannes Gutenberg-University Mainz 1 , Hanns-Dieter-Hüsch-Weg 15, 55128 Mainz , Germany

3. Svenja Morsbach

   Max Planck Institute for Polymer Research

   Affiliation as printed

   Max Planck Institute for Polymer Research 4 , Ackermannweg 10, 55128 Mainz , Germany

4. Bérengère Abou

   Centre National de la Recherche Scientifique · Université Sorbonne Nouvelle · Laboratoire Matière et Systèmes Complexes

   Affiliation as printed

   Matière et Systèmes Complexes (MSC), UMR CNRS 7057, Université de Paris 3 , 75205 Paris Cedex 13 , France

5. Florian Menzel corresponding

   Johannes Gutenberg University Mainz

   Affiliation as printed

   Institute of Organismic and Molecular Evolution (iomE), Johannes Gutenberg-University Mainz 1 , Hanns-Dieter-Hüsch-Weg 15, 55128 Mainz , Germany