Effects of carvacrol on oocyte development in semi-engorged Rhipicephalus sanguineus sensu lato females ticks (Acari: Ixodidae).

•The carvacrol was dose-dependent in the oocytes of semi-engorged females of Rhipicephalus sanguineus sensu lato.•The results showed that the lower concentration (20 μL/mL), the main alterations were: folds at the cellular boundary, irregularities in the germinal vesicle and cytoplasmic vacuolations.•The highest concentration (100 μL/mL), inhibiting the oocyte development, since in this dosage only oocytes were found in the initial stage (I and II).