@article {13915,
	title = {Physiological and biochemical analysis of overwintering and cold tolerance in two Central European populations of the spruce bark beetle, Ips typographus},
	journal = {Journal of Insect Physiology},
	volume = {57},
	number = {8},
	year = {2011},
	month = {August},
	pages = {1136-1146},
	abstract = {Overwintering success is one of the key aspects affecting the development and outbreaks of the spruce bark beetle, Ips typographus (L.) populations. This paper brings detailed analysis of cold tolerance, and its influence on overwintering success, in two Central European populations of I. typographus during two cold seasons. Evidence for a supercooling strategy in overwintering adults is provided. The lower lethal temperature corresponds well to the supercooling point that ranges between -20 and -22 [degree]C during winter months. The supercooled state is stabilized by the absence of internal ice nucleators and by seasonal accumulation of a mixture of sugars and polyols up to the sum concentration of 900 mM. The cryoprotective function of accumulated metabolites is probably based on increasing the osmolality and viscosity of supercooled body fluids and decreasing the relative proportion of water molecules available for lethal formation of ice nuclei. No activity of thermal hysteresis factors (stabilizers of supercooled state) was detected in hemolymph. Lethal times for 50\% mortality (Lts50) in the supercooled state at -5, -10 or -15 [degree]C are weeks (autumn, spring) or even months (winter), suggesting relatively little mortality caused by chill injury. Lts50 at -15 [degree]C are significantly shorter in moist (6.9 days) than in dry (>42 days) microenvironment because there is higher probability of external ice nucleation and occurrence of lethal freezing in the moist situation.},
	keywords = {Ips typographus},
	isbn = {0022-1910},
	author = {Kostal, V. and Dolezal, P. and Rozsypal, J. and Moravcova, M. and Zahradnickova, H. and Simek, P.}
}
@article {13916,
	title = {Multiple component system of sugars and polyols in the overwintering spruce bark beetle, Ips typographus},
	journal = {Journal of Insect Physiology},
	volume = {53},
	number = {6},
	year = {2007},
	month = {June},
	pages = {580-586},
	abstract = {Overwintering adults of the spruce bark beetle, Ips typographus (L.) showed an unusually complex sugar/polyol cryoprotectant system. The major components of the multiple system were: glucose (177.6 mmol L-1, March); trehalose (175.0 mmol L-1, December); sorbitol (147.9 mmol L-1, January); mannitol (81.2 mmol L-1, March); and erythritol (40.7 mmol L-1, March) (in the parentheses, the maximum concentrations are shown and the month when they were reached). Other minor components were glycerol, fructose, threitol, myo-inositol, arabinitol and ribitol. Distinct seasonal patterns of accumulation/depletion in various components were found. Glycerol, trehalose and glucose started to accumulate first, during early autumn, when the air temperatures fluctuated between 20 and 0 [degree]C, and diapause beetles continued in feeding. Glycerol was depleted, glucose remained stable and trehalose continued in accumulation during late autumn when the temperatures oscillated around 0 [degree]C. During early winter severe frosts reaching -20 [degree]C came, the beetles terminated their diapause and trehalose was partially depleted, while mannitol, sorbitol, fructose, threitol and erythritol started to accumulate. Cold weather continued also during late winter when the beetles remained quiescent. During this period, trehalose was re-accumulated, threitol and erythritol continued to increase, mannitol remained stable and sorbitol, fructose decreased. All cryoprotectans were finally cleared in the beetles which were spontaneously leaving bark during early spring. The seasonal maximum of total concentration of all cryoprotectants (578.2 mOsmol L-1) was reached in March. Such a concentration results in colligative depression of melting point of body fluids down by 1.08 [degree]C only. It suggests that the potential cryoprotective effect of accumulated sugars and polyols was related rather to their non-colligative functions},
	keywords = {Ips typographus},
	isbn = {0022-1910},
	author = {Kostal, V. and Zahradnickova, H. and Simek, P. and Zeleny, J.}
}
