Sonia Maria Lauer de Garcia

Regionalization of oviducts in Boophilus microplus (Canestrini, 1887) (Acari: Ixodidae) and its potential significance for fertilization

The structural analysis of oviducts in Boophilus microplus (Canestrini, 1887) in different stages of ingurgitation has indicated that they are constituted primarily of an internal cylinder and an external cylinder with different cell types being found between them. Copulated females in active ingurgitation process show typical variations along the internal cylinder, and three regions can be defined: anterior, ring-like and transitional. Based on such regionalization, hypotheses were raised about where and how fertilization takes place, a process yet to be clarified for the acari.

New histochemical and morphological findings in the female genital tract of Boophilus microplus (Acari, Ixodidae): an attempt toward the elucidation of fertilization in ticks

At present not only is the site of fertilization in ticks still unknown but it is also unclear as to how this mystery can be solved. Signs of fertilization can be observed throughout the female genital tract and these can be clues for the elucidation of the unsolved questions relating to ticks fertilization. In Boophilus microplus (Canestrini, 1887) the most important signs are the following: the final eversion of the acrosomal canal in females ready for oviposition; the presence of small tubules, resembling the subplasmalemal process of the spermatozoon between the oviduct cells; budding nuclei throughout the female genital tract; and the two Feulgen and DAPI positive areas in the oocyte at vitelogenesis. These morphological characteristics suggest that fertilization takes place in the internal cylinder which extends from the uterus to the ovary itself.

Mitotic and meiotic chromosomes of a southern Brazilian population of Boophilus microplus (Acari, Ixodidae)

Using conventional staining with acetic orcein and C-banding techniques it was investigated constitutive heterochromatin chromosomal polymorphisms and the mitotic and the meiotic behavior of male and female chromosomes of Boophilus microplus (Canestrini, 1887). Some differences were detected in the population of southern Brazil as compared to the data of other authors for populations in other latitudes. The differences being mainly concerned with the distribution of constitutive centromeric heterochromatin and variation in the length of heterochromatic blocks in the pericentromeric regions of some chromosome pairs.

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

Summary In the ticks the exact site and mechanism of fertilization is still largely unknown. This study on Boophilus microplus females describes the significant changes in the morphology and histology of the oviducts which occurs from feeding until oviposition. Our results show that in B. microplus the oviducts are formed by an internal and an external cylinder. The internal cylinder is divided into a main region, a ring-like region and a transitional region. 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 contractile and granular cells. The ovary does not have granular cells. The cylinders are externally invested with a membrane. The internal cylinder extends 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 mechanism of fertilization. These observations suggest that the cells of the internal cylinder, including funicular cells, might be oocytes.

The male genital accessory gland complex of the cattle tick Boophilus microplus (Canestrini, 1887) (Acari: Ixodidae)

A topographical and histological study of the male genital accessory gland complex of Boophilus microplus was undertaken. Ten lobes were found, the most prominent of which is the single dorso-median lobe, subdivided into antero-dorsal and postero-dorsal lobes. The other lobes are: a pair of postero-ventral lobes, a pair of lateral lobes (subdivided into dorso-lateral and postero-lateral lobes), a pair of antero-ventral lobes, a single medio-ventral lobe and a pair of latero-ventral lobes. These lobes were observed to present individual topographical and histological characteristics, with independent openings, hence the conclusion is that they form a gland complex. The secretory nature of the dorso-median lobe duct was also analysed.