title: Physiology of cold tolerance in the bark beetle, Pityogenes chalcographus and its overwintering in spruce stands.
abstract: The seasonal development of physiological features underlying gradual acquisition of relatively high cold tolerance in overwintering adults of the bark beetles, Pityogenes chalcographus was described. Prior to overwintering, the beetles accumulated carbohydrate reserves in the form of glycogen and trehalose. These reserves were partially converted to glycerol during peaking winter so that glycerol concentration reached 1.4M in average, which corresponds to approximately one quarter of the beetle dry mass. Whole body supercooling points decreased from -12.8°C in average at the beginning of dormancy (August) to -26.3°C in average during peaking winter (January). More than 75% of January-collected beetles survived at -5°C for 30days, at -15°C for 60days and more than 40% of them survived at -26°C for 12h. High resistance against inoculation of body fluids with external ice crystals, and low mortality, was observed when January-collected beetles were encased in an ice block for 14days. Thus, the physiological limits of cold tolerance measured at individual level in laboratory were safely sufficient for survival of P. chalcographus at any conceivable cold spell that may occur in Central Europe. In contrast, the field experiment showed that winter survival fluctuated between 23.8% and 69.2% at a population level depending on microclimatic conditions in different altitudes and overwintering locations (standing tree trunk or ground level). The meaning of laboratory-assessed physiological limits of cold tolerance for predictions of population winter survival in the field is discussed.
authors.affiliation: Institute of Entomology, Biology Centre ASCR, České Budějovice, Czech Republic; Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic. Electronic address: kostal@entu.cas.cz.
authors.forename: Vladimír
authors.initials: V
authors.lastname: Koštál
authors.affiliation: Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
authors.forename: Bořek
authors.initials: B
authors.lastname: Miklas
authors.affiliation: Institute of Entomology, Biology Centre ASCR, České Budějovice, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Doležal
authors.affiliation: Institute of Entomology, Biology Centre ASCR, České Budějovice, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Rozsypal
authors.affiliation: Institute of Entomology, Biology Centre ASCR, České Budějovice, Czech Republic.
authors.forename: Helena
authors.initials: H
authors.lastname: Zahradníčková
mesh_terms: D000818:Animals; D003080:Cold Temperature; D018153:Czech Republic; D005990:Glycerol / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism*; D006605:Hibernation; D008136:Longevity; D008834:Microclimate; D028222:Picea / Q000469:parasitology; D012621:Seasons; D014199:Trehalose / Q000378:metabolism*; D048889:Weevils / Q000502:physiology*
chemical_list: D006003:Glycogen; D014199:Trehalose; D005990:Glycerol
keywords: Cold hardiness; Glycerol; Glycogen; Ice nucleation; Supercooling; Winter survival