Influence of temperature on the hygropreference of the Collembolan, Cryptopygus antarcticus, and the mite, Alaskozetes antarcticus from the maritime Antarctic

The hygropreference of adult Cryptopygus antarcticus and Alaskozetes antarc ticus was investigated over 2 h at 5, 10 and 20 degreesC, along humidity gr adients (9-98% RH) established by means of different salt solutions. Two ch amber arrangements were employed, linear and grid, to determine any influen ce of thigmotactic behaviour on distribution within the RH gradient. The hu midity preference of both species Varied with temperature. At 5 and 10 degr eesC, C. antarcticus distributed homogeneously showing no clear RH preferen ce. At 20 degreesC, this species preferred the highest humidity (98% RH). A . antarcticus demonstrated a preference for the lowest humidity (9% RH) at 5 degreesC, but at 10 degreesC its distribution differed between the two ar ena types. At 20 degreesC, A. antarcticus showed no clear humidity preferen ce. Assays to control for experimental asymmetries along the gradient; thig motactic behaviour; and aggregative behaviour exclude these factors as expl anations for the observed results. The mean initial water content of sample s did not differ significantly between temperature regimes (C. antarcticus: 68.6, 71.1 and 74.3%; A. antarcticus: 68.1, 70.1 and 68.6% at 5, 10 and 20 degreesC respectively), but the level of water loss increased significantl y with temperature. The influence of desiccation tolerance and the ecologic al significance of the observed humidity preferences are discussed. (C) 200 0 Elsevier Science Ltd. All rights reserved.