Diurnal variation in supercooling points of three species of Collembola from Cape Hallett, Antarctica

• Published in: Journal of insect physiology Vol. 49; no. 11; pp. 1049 - 1061
• Main Authors: Sinclair, Brent J., Jaco Klok, C., Scott, Matthew B., Terblanche, John S., Chown, Steven L.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.11.2003
• Subjects: Acclimation; Acclimatization - physiology; Algae; Animal Nutritional Physiological Phenomena; Animals; Antarctic Regions; Arthropods - physiology; Behavioural avoidance; Body Water - physiology; Circadian Rhythm - physiology; cold; Cold Temperature; Cold tolerance; cooling; Cryptopygus cisantarcticus; diurnal variation; foraging; Friesea grisea; heat; hemolymph; Hemolymph - metabolism; Isotoma klovstadi; Isotomidae; lichens; microclimate; Microclimate temperature; migratory behavior; mosses and liverworts; Neanuridae; osmolality; Osmolar Concentration; Rapid cold hardening; relative humidity; Seasons; Starvation - metabolism; Statistical Distributions; summer; supercooling; supercooling point; Temperature; Time Factors; water content; Antarctica; Antarctic Regions; Microclimate temperature; Rapid cold hardening; Cold tolerance; Behavioural avoidance; Acclimation
• ISSN: 0022-1910; 1879-1611
• DOI: 10.1016/j.jinsphys.2003.08.002

Daily changes in microclimate temperature and supercooling point (SCP) of Collembola were measured during summer at Cape Hallett, North Victoria Land, Antarctica. Isotoma klovstadi and Cryptopygus cisantarcticus (Isotomidae) showed bimodal SCP distributions, predominantly in the high group during the day and in the low group during the night. There were no concurrent diurnal changes in water content or haemolymph osmolality. By contrast, Friesea grisea (Neanuridae) had a unimodal distribution of SCPs that was invariant between daytime and nighttime. Isotoma klovstadi collected foraging on moss had uniformly high SCPs, which shifted towards the low group when the animals were starved for 2–8 h. When I. klovstadi was acclimated for five days with lichen or algae, SCPs were higher than if they were supplied with moss, while those that were starved (with free water or 100% relative humidity) displayed a trimodal SCP distribution. A variety of pre-treatments, including cold, heat, desiccation and slow cooling were ineffective at inducing SCP shifts in C. cisantarcticus or I. klovstadi. It is postulated that behavioural avoidance of low temperatures by vertical migration may be key in I. klovstadi’s short-term survival of nighttime temperatures. These data suggest that the full range of thermal responses of Antarctic Collembola is yet to be elucidated.