Similarity in critical transition temperature for ticks adapted for Different Environments: studies on the Water balance of Unfed Ixodid Larvae

Abstract

Unfed tick larvae were used to gain insight into the critical transition temperature (CTT) due to their absence of spiracles. The study consisted of five species of medical-veterinary importance, Amblyomma americanum (L.), Amblyomma maculatum Koch, Dermacentor variabilis (Say), Ixodes scapularis Say and Rhipicephalus sanguineus (Latreille). Results show that each species has its own characteristic water loss rate consistent with ecological classification. The lowest water loss rates were recorded for the dry-adapted R. sanguineus, and the highest rates were observed for more hydrophilic species,/. scapularis and A. americanum. Body water content averaged 61% and appears to be a useful secondary characteristic for ecological classification, as xeric-adapted species had slightly lower water content. For each of the species examined, a loss in the ability to retain water indicative of a CTT occurred between 30-35 °C in spite of these differences in water loss rate and water content, suggesting that this threshold is not species-specific and has little value for predicting habitat preference. An explanation for the similarity is that the CTT is independent of the lipid melting model as demonstrated by Boltzmann temperature function on an Arrhenius plot. Killed larvae (freezing or HCN) also showed a CTT of 30-35 °C revealing for the first time that heightened respiratory metabolism and inoperable spiracular closing mechanisms as the temperature rises play a minimal role in transition phenomena. Evidence implies that CTT is a stage-specific characteristic that may serve as a protective mechanism to cluster larvae in microhabitats with high moisture content.

Using environmental factors to predict Rhipicephalus sanguineus s.l. (Acari: Ixodidae) mortality

“…This may be due to a low water loss rate in Rhipicephalus sanguineus s.l. as compared to other ticks 16 . This extended indoor survival time has been one of the challenges for Rhipicephalus sanguineus s.l.…”

“…as compared to other ticks. 16 This extended indoor survival time has been one of the challenges for Rhipicephalus sanguineus s.l. management and may extend the duration of the control period required for the elimination of residential infestations.…”

Modeling Potential Habitat for Amblyomma Tick Species in California

“…Mortality for this species is high at temperatures ≤–3.5°C [68], but between 2014 and 2018, average temperatures along most of the California coast did not fall below 5 °C. Amblyomma americanum is unable to withstand high temperatures, with a critical transition temperature (the threshold at which the cuticular lipids of the tick “melt” and are no longer able to prevent water loss, leading to desiccation) of 30–35 °C [69], constraining habitat to the mild and narrow temperature range such as occurs along the Californian coast. This species also requires high humidity [69,70], which occurred on the coast but also resulted from high levels of summer precipitation in the north of California and in the Sierra Nevada.…”

“…Amblyomma americanum is unable to withstand high temperatures, with a critical transition temperature (the threshold at which the cuticular lipids of the tick “melt” and are no longer able to prevent water loss, leading to desiccation) of 30–35 °C [69], constraining habitat to the mild and narrow temperature range such as occurs along the Californian coast. This species also requires high humidity [69,70], which occurred on the coast but also resulted from high levels of summer precipitation in the north of California and in the Sierra Nevada. Human pathogens for which A. americanum is a competent vector have been reported from areas of coastal and northern California predicted to be suitable for the tick, including E. chaffeensis [71] and F. tularensis [72].…”

A Lack of “Environmental Earth Data” at the Microhabitat Scale Impacts Efforts to Control Invasive Arthropods That Vector Pathogens

“…Within these isolated and sheltered microhabitats environmental conditions can be very different to those in the surrounding environment. In the same way, IAVPs can be sensitive to extreme environmental conditions, for example the lone star tick (Amblyomma americanum [Linnaeus, 1758]), which is invasive across much of the north east of the USA, dies within just 2 h of exposure to temperatures of ≤−3 • C in the laboratory [52] and rapidly desiccates when exposed for several hours to temperatures exceeding 30 • C [53]. Likewise, mortality of Culicoides brevitarsis [Kieffer, 1917] (Diptera: Ceratopogonidae), a vector of the bluetongue virus, is high in the laboratory when temperatures are greater than 35 • C, even if just for a few days [54].…”