Efeito de diferentes temperaturas sobre a fase não parasitária de Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodida) adaptado a clima temperado

Abstract

The recent infestation of dogs by Rhipicephalus sanguineus, in a region of temperate climate in southern Brazil, generated the need to know the thermal sensitivity of this population to understand its mechanism of adaptation. Engorged females were collected directly from dogs, in the municipality of Santa Vitória do Palmar, State of Rio Grande do Sul, Brazil. The females were weighed and organized into groups of 30 individuals by temperature. They were individually incubated in a BOD incubator at 15, 25, 27, and 31ºC, relative humidity (RH) ≥ 80%. Biological parameters, like of pre and laying periods, egg mass, hatchability, inter alia, were daily evaluated. It was found that the reduction of the incubation temperature caused less reproductive efficacy and prolongation of biological stages of the tick, similar to those observed in other populations. This prolongation allows it to survive the period of local low temperatures. A constant temperature of 15ºC prevented embryogenesis, but allowed the laying of fertile and viable eggs when exposed to higher temperatures. The survive of this species in the region is due to its habit of living under their hosts what protect it from extreme temperatures, the ability to prolong the cycle, and the fact that, even during the period of low temperatures, increases occur daily, allowing embryogenesis of some individuals, capable of maintaining the population.