Some remarks on the cytogenetics of oribatid mites

Abstract

The behaviour of the meiotic segregations of the parthenogenetic oribatid mite Archegozetes longisetosus Aoki were investigated in maturing oocytes. Data about the meiotic mechanisms in parthenogenetic oribatid mites are very sparse, although the mechanism of reproduction is fundamental for the restoration of diploidy and has different consequences for the genotype of the offspring. For our analyses we used a combination of traditional methods and the novel technique of synchrotron X-ray holotomography. We describe the points in maturation at which the meiotic segregations occur and the positions of the oocytes at this time in the female genital tract. As the position of the nuclei in the first segregation is located beneath the cell membrane and in the second one central in the cell, we believe to have evidence for an inverted meiotic sequence.