Changes in the oviducts after the fertilization of the cattle tick Boophilus microplus (Canestrini, 1887) (Acari : Ixodidae)

In the ticks the exact site and mechanism of fertilization is still largely unknown. This study on Boophilus microplus females describes the significa nt changes in the morphology and histology of the oviducts which occurs fro m feeding until oviposition. Our results show that in B. microplus the ovid ucts are formed by an internal and an external cylinder. The internal cylin der is divided into a main region, a ring-like region and a transitional re gion. The cells of the main region maintain close contact with spermatozoa, while in the ring-like region there are no spermatozoa, and only when this region disappears, spermatozoa are found in the ovary even at oviposition. The space between the cylinders contains several cell types, including con tractile and granular cells. The ovary does not have granular cells. The cy linders are externally invested with a membrane. The internal cylinder exte nds throughout the length of the reproductive system from the uterus to the ovary itself, and this suggests that the internal cylinder is not merely a passageway for spermatozoa and ova but might be actively involved in the m echanism of fertilization. These observations suggest that the cells of the internal cylinder, including funicular cells, might be oocytes.