Macroscopically, the Bidder’s organ is observed in close association with the ovary (Figs. 2 and 3). The Bidder’s organs were found in seven females. In two females with fully grown postvitellogenic ovarian follicles, the Bidder’s organs could not be seen.
The ovary consists of a thin sheath of connective tissue, enclosing the ovarian follicles and visualized at different stages of development (Fig. 4). The ovarian follicles consist of germ cells surrounded by a follicular cell layer. The germ cells display a large nucleus with several prominent nucleoli. The ovary is a sac-shaped structure without a typical medullar region.
Bidderian follicles at different stages of development are shown (Fig. 4). Germ cells display a rounded nucleus, and are enclosed by a layer of follicular cells, varying from flat to cubic. Light microscopy images reveal typical Bidder’s organ in close spatial relationship with ovary. In some cases, continuity between both organs is observed (Fig. 4).