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

Abstract

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.Key words: acari, ticks, female reproductive system, fertilization. RESUMORegionalizações dos ovidutos em Boophilus microplus (Canestrini, 1887) (Acari:Ixodidae) e seu possível significado na fecundação.Uma análise estrutural dos ovidutos de Boophilus microplus (Canestrini, 1887) em diferentes fases de ingurgitamento permitiu detectar que eles estão constituídos basicamente por dois cilindros celulares, um interno e outro externo; entre os quais foram encontrados diferentes tipos celulares. Fêmeas copuladas e em processo ativo de ingurgitamento mostram variações típicas ao longo do cilindro interno podendo ser definidas três regiões: anterior, anelar e de transição. Com base em tal regionalização, hipóteses sobre onde e como ocorre a fecundação, processo ainda não elucidado até o momento para ácaros, são levantadas.Palavras-chave: ácaros, carrapatos, aparelho reprodutor feminino, fertilização.

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

“…Budding nuclei might be indicative of syngamy as shown by the fact that they appear in oviduct cells only near spermatozoa and that, in the ovary, budding nuclei appear in the interstitial cells which are the first cells to make contact with spermatozoa coming through the lumen of the ovary. We suggest that cells with budding nuclei are cells of the internal cylinder (GARCÍA-FERNÁNDEZ et al, 1999, 2001, which extends itself into the ovary. Budding nuclei representing expulsion of DNA from the female nucleus as an alternative to reductional divisions seems very improbable.…”

“…At the very beginning of engorgement the spermatozoa are found throughout the genital tract from uterus to the ovary but as engorgement progresses the spermatozoa are impeded from proceeding toward the ovary by the formation of a ring-like structure in the oviduct close to the ovary (GARCÍA-FERNÁNDEZ et al, 1999, 2001, the access to the ovary occurring when this structure disappears and the female is ready for ovulation.…”

“…AESCHLIMANN (1958) in O. moubata andTILL (1961) in Rhipicephalus appendiculatus (Neumann, 1901). GARCÍA-FERNÁNDEZ et al (1999) described the oviduct of B. microplus as being formed by two concentric cylinders made up of different cell types, with the internal cylinder extending throughout the whole female genital tract from the oviducts to the ovary. These authors have also suggested that the internal cylinder functions as a germarium, while the ovary acts as a vitellarium, with fertilization occurring throughout the internal cylinder (GARCÍA-FERNÁNDEZ et al, 2001).…”