Diurnal variation in supercooling points of three species of Collembola from Cape Hallett, Antarctica.
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.
Sinclair
Brent J
BJ
Spatial, Physiological and Conservation Ecology Group, Department of Zoology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa. bjs@sun.ac.za
Jaco Klok
C
C
Scott
Matthew B
MB
Terblanche
John S
JS
Chown
Steven L
SL
D000064:Acclimatization / Q000502:physiology*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D000864:Antarctic Regions; D001181:Arthropods / Q000502:physiology*; D001834:Body Water / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D003080:Cold Temperature; D006458:Hemolymph / Q000378:metabolism; D009994:Osmolar Concentration; D012621:Seasons; D013217:Starvation / Q000378:metabolism; D016008:Statistical Distributions; D013696:Temperature; D013997:Time Factors