Ovarian structure and oogenetic cycle in the millipede Catamicrophyllum caifanum (Diplopoda: Iulidae)

Abstract

The ovaries and oocytes of a iulid millipede Catamicrophyllum caifanum Verhoeff 1920, were studied in an oak woodland and a planted pine forest in the Mediterranean region in northern Israel. The changes in the stages and number of oocytes are described throughout the activity period of this millipede: October–February. Four stages of female germ cell development could be distinguished: (1) the early stages of oogenesis when the female germ cells (= oogonia) are still embedded in the germ layers of the ovarian epithelium; (2) two sizes of previtellogenic oocytes entering the ovarian lumen are distinguishable. Small ones (< 0.1 mm) observable only in microscopic sections, and larger ones (0.2–0.45 mm) that could be seen under the dissecting microscope. The small previtellogenic oocytes were present in the ovary throughout the study period. The oocytes apparently undergo vitellogenesis during autumn; (3) with the accumulation of yolk, a third stage consisting of small, medium and large vitellogenic oocytes can be discerned; (4) the mature, post-vitellogenic oocytes, elliptic in shape and yellowish in colour, appear towards the end of autumn. In winter only post-vitellogenic oocytes are found, disappearing from the ovary towards the end of winter. The number of mature, post-vitellogenic oocytes is positively correlated with the female's body size. Catamicrophyllum caifanum has therefore an annual oogenetic cycle breeding once yearly during winter. This, together with the fact that its ovary contains oocytes belonging to different stages (= generations), indicates that it can breed at least four and possibly up to seven times during its lifetime.