کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5546505 | 1402745 | 2016 | 7 صفحه PDF | دانلود رایگان |
Understanding how ticks survive the multitude of stresses experienced during winter is integral to predicting population dynamics and transmission of tick-borne pathogens. The American dog tick (Dermacentor variabilis), a predominant vector of Rocky Mountain spotted fever, overwinters in any of its post-egg life stages. In this study, we characterized the cold tolerance of larval D. variabilis and examined the effect of various acclimatory conditions on cold hardiness. Cold-shock survival during 2 h exposure to various subzero temperatures was assessed and a lower lethal temperature of â20 °C and a 50% mortality temperature near â16 °C was established. Larvae exposed to â5 °C showed high survival (â¼70%) after 14 d and near 50% for up to 56 d at â5 °C. Larvae cycled between supra- and subzero temperatures showed better long-term survival than at constant â5 °C. The temperature of crystallization (Tc) was â¼â23 °C and no larvae survived freezing after reaching their Tc. Larvae exposed to inoculative freezing survived brief, mild treatments (70% survival of â5 °C for 2 h) but survival was reduced compared to larvae cooled in the absence of ice. Reduced photophase, rapid cold hardening, dehydration, and long-term thermal acclimation all improved larval cold hardiness to varying degrees. Survival data were compared to measurements of hibernacula conditions, and we conclude that larvae face little threat from cold-induced mortality but inoculative freezing does pose a risk, and the geographic distribution of D. variabilis is only minimally influenced by the ability of larvae to survive low temperature exposure.
Journal: Ticks and Tick-borne Diseases - Volume 7, Issue 6, October 2016, Pages 1155-1161