Ovarian morphology in two species of Pseudonannolene (Diplopoda, Arthropoda)

ABSTRACT

The anatomy of the gametes and reproductive system of millipedes is important in establishing the phylogenetic relationshisps of this group with other arthropods. The genus Pseudonannolene (Spirostreptida) has the most derivedmale reproductive system among millipedes. In contrast, little is known about the female reproductive system. In this study, we describe the ovarian morphology of two species of Pseudonannolene. In both species, the ovaries consisted of a single tube in which oocystes in different developmental stages were observed. These oocytes were randomly distributed throughout the gonad. A region similar to a germarium was present at the anterior extremity of the tube, which suggested the presence of a single apical germination center. Since the pairing of ovarian structures is considered a primitive character, the two species examined here showed the most derived model of ovarian structure described so far among millipedes. This conclusion agrees with similar observations for the male reproductive system of this genus.