Larval thermal characteristics of multiple ixodid ticks

Temperature limits the geographic ranges of several tick species. Little is known about the thermal characteristics of these pests outside of a few studies on survival related to thermal tolerance. In this study, thermal tolerance limits, thermal preference, and the impact of temperature on activity levels and metabolic rate were examined in larvae for six species of ixodid ticks. Tolerance of low temperatures ranged from -15 to -24 degrees C with Dermacentor andersoni surviving the lowest temperatures. High temperature survival ranged from 41 to 47 degrees C, with Rhipicephalus sanguineus sensu lato having the highest upper lethal limit. Ixodes scapularis showed the lowest survival at both low and high temperatures. Thermal preference temperatures were tested from 0 to 41 degrees C. The majority of species preferred temperatures between 17 and 22 degrees C, while Dermacentor variabilis preferred significantly lower temperatures, near 12 degrees C. Overall activity was measured across a range of temperatures from 10 to 60 degrees C, and most tick species had the greatest activity near 30 degrees C. Metabolic rate was the greatest between 30 and 40 degrees C for all tick species and was relatively stable from 5 to 20 degrees C. The optimal temperature for tick larvae is likely near the thermal preference for each species, where oxygen consumption is low and activity occurs that will balance questing and conservation of nutrient reserves. In summary, tick species vary greatly in their thermal characteristics, and our results will be critical to predict distribution of these ectoparasites with changing climates.

Automated summary

This study examined the thermal tolerance limits and thermal preference of six species of ixodid tick larvae, finding variations in survival rates and activity levels at different temperatures. Most tick species preferred temperatures between 17 and 22 degrees Celsius, while Dermacentor variabilis favored significantly lower temperatures.