Comparative biology between a tropical-equatorial and temperate population of Rhipicephalus microplus from Brazil

In the present study, we evaluated and compared the in vitro biological parameters of the evolutionary stages of R. microplus (female, eggs, and larva) from two extreme regions of Brazil: Santa Rita (SR) northeast region and Bagé (BG) southern region. For this, all stages were maintained at 23, 27, and 32°C with a relative humidity (RH) of 65, 80, and 100%. The mean incubation period was 43.7 to 53.7 days (SR population) and 59.0 to 56.1 days (BG population) at 23°C and 18.0 to 19.3 days (SR population) and 16.8 to 21.2 days (BG population) at 32°C. Eggs incubated at 23°C (65, 80, and 100% RH) of SR and BG populations showed a similar egg hatching percentage (P > 0.05). The egg hatching percentage of the SR population (30.5 to 98.0%) was always higher than that of the BG population (8.7 to 85.5%; P < 0.05) when incubated at 32°C and 65, 80, or 100% RH. Deleterious effects on the larval survival period from SR and BG were observed under all experimental conditions (temperature and RH), especially at 23 and 32°C. However, they were more intense on larvae at 32°C (all RH). Under 80 and 100% RH, the mean period of larval survival did not exceed 65 days, being shortest for the BG population (mean: 42.7 days [80% RH] and 55.1 days [100% RH]) compared with the SR population.