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Abstract Ticks are obligatorily hematophagous but spend the majority of their lives off host in an unfed state where they must resist starvation between bouts of blood feeding. Survival during these extended off‐host periods is critical to the success of these arthropods as vectors of disease; however, little is known about the underlying physiological and molecular mechanisms of starvation tolerance in ticks. We examined the bioenergetic, transcriptomic and behavioural changes of female American dog ticks,Dermacentor variabilis, throughout starvation (up to nine months post‐bloodmeal). As starvation progressed, ticks utilized glycogen and lipid, and later protein as energy reserves with proteolysis and autophagy facilitating the mobilization of endogenous nutrients. The metabolic rate of the ticks was expectedly low, but showed a slight increase as starvation progressed possibly reflecting the upregulation of several energetically costly processes such as transcription/translation and/or increases in host‐seeking behaviours. Starved ticks had higher activity levels, increased questing behaviour and augmented expression of genes related to chemosensing, immunity and salivary gland proteins. The shifts in gene expression and associated behavioural and physiological processes are critical to allowing these parasites to exploit their ecological niche as extreme sit‐and‐wait parasites. The overall responses of ticks to starvation were similar to other blood‐feeding arthropods, but we identified unique responses that could have epidemiological and ecological significance for ticks as ectoparasites that must be tolerant of sporadic feeding.
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Function and evolution of the aquaporin IsAQP1 in the Lyme disease vector Ixodes scapularis
Abstract Ticks are important vectors of pathogenic viruses, bacteria, and protozoans to humans, wildlife, and domestic animals. Due to their life cycles, ticks face significant challenges related to water homeostasis. When blood‐feeding, they must excrete water and ions, but when off‐host (for stretches lasting several months), they must conserve water to avoid desiccation. Aquaporins (AQPs), a family of membrane‐bound water channels, are key players in osmoregulation in many animals but remain poorly characterized in ticks. Here, we bioinformatically identified AQP‐like genes from the deer tickIxodes scapularisand used phylogenetic approaches to map the evolution of the aquaporin gene family in arthropods. Most arachnid AQP‐like sequences (including those ofI. scapularis) formed a monophyletic group clustered within aquaglycerolporins (GLPs) from bacteria to vertebrates. This gene family is absent from insects, revealing divergent evolutionary paths for AQPs in different hematophagous arthropods. Next, we sequenced the full‐length cDNA ofI. scapularisaquaporin 1 (IsAQP1) and expressed it heterologously inXenopusoocytes to functionally characterize its permeability to water and solutes. Additionally, we examinedIsAQP1expression across different life stages and adult female organs. We foundIsAQP1is an efficient water channel with high expression in salivary glands prior to feeding, suggesting it plays a role in osmoregulation before or during blood feeding. Its functional properties are unique: unlike most GLPs,IsAQP1has low glycerol permeability, and unlike most AQPs, it is insensitive to mercury. Together, our results suggestIsAQP1plays an important role in tick water balance physiology and that it may hold promise as a target of novel vector control efforts.
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- Award ID(s):
- 1645331
- PAR ID:
- 10428796
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Insect Molecular Biology
- Volume:
- 32
- Issue:
- 4
- ISSN:
- 0962-1075
- Page Range / eLocation ID:
- p. 329-339
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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