Cold hardiness and influences of hibernaculum conditions on overwintering survival of American dog tick larvae
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- 作者：Andrew J. Rosendale ; rosendaw@uc.edu" class="auth_mail" title="E-mail the corresponding author ; rosendaj28@gmail.com" class="auth_mail" title="E-mail the corresponding author ; David W. Farrow ; Megan E. Dunlevy ; Alicia M. Fieler ; Joshua B. Benoit
- 关键词：Dermacentor variabilis ; Cold hardiness ; Photoperiod ; Acclimation ; Rapid cold hardening
- 刊名：Ticks and Tick-borne Diseases
- 出版年：2016
- 出版时间：October 2016
- 年：2016
- 卷：7
- 期：6
- 页码：1155-1161
- 全文大小：753 K
文摘
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 −20 °C and a 50% mortality temperature near −16 °C was established. Larvae exposed to −5 °C showed high survival (∼70%) after 14 d and near 50% for up to 56 d at −5 °C. Larvae cycled between supra- and subzero temperatures showed better long-term survival than at constant −5 °C. The temperature of crystallization (Tc) was ∼−23 °C and no larvae survived freezing after reaching their Tc. Larvae exposed to inoculative freezing survived brief, mild treatments (70% survival of −5 °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.