Metabolic rate and resource depletion in the tick Ixodes ricinus in response to temperature
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Metabolic rate and resource depletion in the tick Ixodes ricinus in response to temperature Saeed Alasmari1 · Richard Wall1 Received: 24 August 2020 / Accepted: 4 November 2020 © The Author(s) 2020
Abstract Understanding the effects of temperature on the metabolic activity and the rate of depletion of energy reserves by Ixodes ricinus can represent an important contribution to explaining patterns of tick activity and the likely impacts of environmental change on tick and tick-borne disease risk. Here, a cohort of I. ricinus nymphs, males, and females was collected and placed into incubators at temperatures of between 5 and 30 °C. The protein, carbohydrate, total lipid, neutral lipid, and glycogen levels were measured for nymphs for up to 70 days and adults up to 42 days. In nymphs, at day 0, glycogen was the most abundant metabolite followed by carbohydrate, with relatively low concentrations of protein and lipids. For males, the concentrations of different metabolites were relatively similar. In contrast, for females, concentrations of glycogen and carbohydrate were relatively low compared to those of protein and neutral lipids. Significant exponential declines in metabolite concentrations of all metabolites were detected over time for all life-cycle stages and at all temperatures. Nymphs generally showed lower rates of resource depletion than adults at all temperatures. The lower thresholds for metabolic activity were estimated to be between −10 and −5 °C. The Q 10 values, which describe the thermal sensitivity of metabolic rate, were estimated to be relatively low (1.5 for nymphs, 1.71 for males, and 1.63 for females) compared to insects where they are typically around 2.5 (range: 1.5–3), and this is considered to be an adaptation to increase survival during the extended inter-feed intervals. Keywords Blood-feeding · Climate change · Ixodes · Metabolite · Temperature threshold
Introduction Intermittent blood-feeding and digestion are key behavioural and physiological processes in hard ticks (Ixodidae) that are intimately associated with their role as vectors of pathogens (Randolph 2004). Unlike hematophagous insects, a blood-meal is taken only once by each life-cycle stage: the inter-feed interval is usually several months in univoltine species, ingestion is relatively slow, the volume of blood ingested is relatively large, and digestion is intracellular (Horn et al. 2009; Kongsuwan et al. 2010). Sufficient nutrition must be * Saeed Alasmari [email protected] 1
School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
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Experimental and Applied Acarology
obtained at each meal and stored within the body to allow larvae and nymphs to undergo development to the next life-cycle stage and eventually initiate repeated questing until another host is located. For adults, accumulated metabolic reserves must also provide the resources for reproduction (Diehl et al. 1982). The longer ticks can survive between bloodmeals, the higher the chance of enc
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