Thermal tolerance and cold hardiness strategy of the sub-Antarctic psocid Antarctopsocus jeanneli Badonnel

Despite considerable work on the upper and lower lethal limits of insects, several major taxa have received little attention. We investigated the lower and upper thermal tolerances and cold hardiness strategy of Antarctopsocus jeanneli Badonnel (Psocoptera: Elipsocidae) from sub-Antarctic Marion Island. A. jeanneli is freeze intolerant and, more specifically, moderately chill tolerant. Field fresh A. jeanneli had a mean supercooling point (SCP) of -11.1°C, whereas LT50 was -7.7°C, indicating pre-freeze mortality. A. jeanneli responds to acclimation: mean SCP increased from -15.8°C at a treatment temperature of 0 to -7.3°C at 15°C, as a result of a shift in the proportion of individuals in the high and low groups of the bimodal SCP distribution. A. jeanneli has upper thermal tolerances that are lower than those of other insect species on Marion Island, but within the range of expected microhabitat temperatures. Further study will establish whether freeze intolerance is characteristic of Psocoptera.