Low temperature adaptations in beetles from the Sub-Antarctic Island of South Georgia

Abstract

Adaptations to the Sub-Antarctic climate of South Georgia were studied in four species of Coleoptera. in larvae and adults of Hydromedion sparsutum and Perimylops antarcticus (Perimylopidae) collected during summer, the ability to supercool was increased by low temperature acclimation, and more in specimens from high than from low elevations. Both adults and larvae were killed by freezing at temperatures below-5 to-8°C. Supercooling ability of adult Oopterus soledadinus (Carabidae) also increased slightly with acclimation, while no effect was observed in Halmaeusa atriceps (Staphylinidae). Both species were freezing-intolerant. Potential cryoprotectants present in the beetles were trehalose, glycerol, myoinositol and glucose. The maximum concentrations of individual sugars and polyols ranged from 4–20 μg mg-1 live weight, and were not increased by low temperature acclimation in the laboratory. The life cycles of H. sparsutum and P. antarcticus appear to extend for two or more years. Their adaptations also include brachyptery and the utilisation of mosses for food. None of the species survived anoxia for extended periods.