Rhipicephalus sanguineus sensu lato (s. l.) ticks are targets of acaricidal treatments due to their great veterinary and medical importance. Acetylcarvacrol stands out as a promising acaricidal substance for its increased biocidal activity and stability. Additionally, its toxicity to mammals is reduced when compared to the parent molecule, carvacrol. The present study aimed to evaluate the effects of acetylcarvacrol on the morphology of ovaries of engorged R. sanguineus s. l. ticks. The animals were subjected to the Adult Immersion Test to calculate the lethal concentrations (LC₅₀ and LC₉₀) of acetylcarvacrol. Subsequently, the surviving ticks were dissected for collection of the ovaries. The samples were processed through routine histological techniques. The histological sections were stained with hematoxylin and eosin, bromophenol blue (protein detection) and PAS (polysaccharide detection). The alterations found in the ovaries were evaluated by morphometric and semiquantitative analysis. The LC₅₀ and LC₉₀ were 17.805 and 26.164 μL/mL, respectively. The most severe morphological alterations were disappearance of the female germ cells (oocytes), nucleolus vacuolization, thicker and irregular chorion, and decrease in size of the oocytes. Also, the content of proteins and carbohydrates in the oocytes were heavily affected by the chemical, as evidenced by a non-homogeneous staining pattern. The group exposed to the highest concentration of acetylcarvacrol (20 μL/mL) exhibited a statistically greater score in the semiquantitative analysis when compared to the other groups. The morphological changes in the ovaries may reduce the ticks' offspring production or generate descendants that will struggle to carry out essential biochemical processes during their lives. Thus, acetylcarvacrol may be a promising alternative to control tick infestation by impairing the reproduction of this parasite.

由于其在兽医和医学上的重要性，Rhipicephalus sanguineus sensu lato（sl）tick是杀螨治疗的目标。乙酰香芹酚因其增强的杀生物活性和稳定性而成为一种有前途的杀螨剂。另外，与母体分子香芹酚相比，它对哺乳动物的毒性降低了。针对目前的研究，以评估对充盈的卵巢形态acetylcarvacrol的影响血红SL蜱。对动物进行成人浸没测试以计算致死浓度（LC ₅₀和LC ₉₀）的乙酰香芹酚。随后，解剖幸存的壁虱以收集卵巢。通过常规组织学技术处理样品。组织切片用苏木精和曙红，溴酚蓝（蛋白质检测）和PAS（多糖检测）染色。通过形态计量学和半定量分析评估卵巢中发现的变化。LC ₅₀和LC ₉₀分别为17.805和26.164μL/ mL。最严重的形态学改变是雌性生殖细胞（卵母细胞）消失，核仁空泡化，绒毛膜厚，不规则以及卵母细胞大小减小。同样，卵母细胞中蛋白质和碳水化合物的含量也受到化学物质的严重影响，这是由非均质染色模式所证明的。与其他组相比，暴露于最高浓度的乙酰基香芹酚（20μL/ mL）的组在半定量分析中显示出统计学上更高的得分。卵巢的形态变化可能会减少the的后代产量或产生后代，这些后代将很难在其一生中进行必要的生化过程。因此，