Tolerance to Low Temperatures and Desiccation in Insects from Andean Paramos

Abstract

Adaptations to low temperatures and desiccation were studied in insects from the Andean paramos in Venezuela at 3600 and 4200 m asl. Temperature fluctuations in the paramos range from 15 to 20°C during daytime to below freezing during the night. Two species of carabid beetles (Colpodes spp.) collected within senescent leaves of the Espeletia rosette plants or in sheltered ground microhabitats had low supercooling capacity and were killed by freezing for 1 or 2 h at −50°C. All specimens of the acridid grasshopper Meridacris subaptera that lives in open, exposed habitats, however, survived freezing for 8 h at −6°C, and some survived for 2 h at −9°C. A curculionid beetle from the green Espeletia rosettes apparently survives low temperatures by supercooling. The rates of water loss in the two species of Colpodes at 20°C and 6% RH were 9 and 14 mg H₂O·g⁻¹·h⁻¹ and 43 mg H₂O·g⁻¹·h⁻¹ in a species of Opiliones from moist, senescent Espeletia leaves. In contrast, juveniles of Meridacris subaptera lost only 2 mg H₂O·g⁻¹·h⁻¹ under the same conditions. At 30°C and 6% RH, rates of water loss in juveniles and adults of this species ranged from 3 to 5 mg H₂O·g⁻¹·h⁻¹, comparable to those of desert insects.