SUMMARYLarvae of the freeze-avoiding beetle Cucujus clavipes puniceus (Coleoptera: Cucujidae) in Alaska have mean supercooling points in winter of -35 to -42°C, with the lowest supercooling point recorded for an individual of -58°C. We previously noted that some larvae did not freeze when cooled to -80°C, and we speculated that these larvae vitrified. Here we present evidence through differential scanning calorimetry that C. c. puniceus larvae transition into a glass-like state at temperatures <-58°C and can avoid freezing to at least -150°C. This novel finding adds vitrification to the list of insect overwintering strategies. While overwintering beneath the bark of fallen trees, C. c. puniceus larvae may experience low ambient temperatures of around -40°C (and lower) when microhabitat is un-insulated because of low snow cover. Decreasing temperatures in winter are correlated with loss of body water from summer high levels near 2.0 to winter lows near 0.4mgmg ) and thermal hysteresis. Finally, we provide direct evidence that Cucujus from Wiseman, Alaska, survive temperatures to -100°C.

Body temperature patterns before, during, and after semi-natural hibernation in the European ground squirrel Hut, Roelof; Barnes, B.M.; Daan, S.; Heldmaier, G. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Abstract Ground squirrels undergo extreme body temperature¯uctuations during hibernation. The eect of low body temperatures on the mammalian circadian system is still under debate. Using implanted temperature loggers, we recorded body temperature patterns in European ground squirrels kept in an enclosure under natural conditions. Although hibernation onset was delayed, hibernation end corresponded closely to that measured in a ®eld population. Circadian body temperature¯uctuations were not detected during deep torpor, but indications of circadian timing of arousal episodes at higher temperatures were found at the beginning and end of hibernation. One male exhibited synchronised arousals to a relatively constant phase of the day throughout hibernation. All animals ®rst entered torpor in the afternoon. Daily body temperature¯uc-tuations were decreased or distorted during the ®rst days after hibernation. We hypothesise that hibernation may aect the circadian system by either decreasing the expression of the circadian oscillator, or by decreasing the amplitude of the circadian oscillator itself, possibly due to gradual, temperature dependent, internal desynchronisation. The latter mechanism may be bene®cial because it might facilitate post-hibernation re-entrainment rates.Keywords Circadian rhythmicity á Torpor á Euthermia á Arrhythmicity á Implantable temperature loggers Abbreviations DD continuous darkness á LD light-dark cycle á SCN suprachiasmatic nuclei