Fig. 2. Histological sections of yellow-mandi ovaries at different stages of gonadal maturation; tissues were fixed in 5% buffered glutaraldehyde and then post-fixed in Bouin's fluid; bars = 100 µm. a) Resting stage: chromatin nucleolar (O1) and perinucleolar (O2) were the only types of oocytes present. b) Maturation stage: besides O1 and O2 oocytes, the ovary contained yolk vesicle oocytes (O3). c) Mature stage: at this stage the ovaries showed chromatin nucleolar (O1), perinucleolar (O2) and vitellogenic (O4) oocytes. d) Spawned stage: postovulatory follicle (POF) was a striking structure present in the ovaries at this stage; atresic oocyte (AO); chromatin nucleolar (O1) and perinucleolar (O2) oocytes were also observed.