Histological structure of the ovary in adult Zebra fish

The reproductive system in Zebra fish is intensely analyzed in research, especially in toxicological studies. Therefore, thorough knowledge about normal histology is vital. In our study we have examined 30 adult Zebra fish females with the aim of description the normal morphology and oocytes stages of development. For the gonads examination, histological samples were realized by cutting the fish in cross section or longitudinal section. Samples were fixed in Bouin, embedded in paraffin, sectioned at 5μm, H&E stained and examined at light microscope Olympus CX41. Oocytes in different stages of development were differentiated, measuredand main structures were noted. Primary oocytes were mainly disposed in clusters, had small diameter, intense basophil cytoplasm, big nucleus and multiple nucleoli, whilst the cortical alveoli oocytes had larger diameter, germinative vesicle highly irregular, with pleiomorphic and multiple nucleoli and mainly the formation of cortical alveoli with different forms and sizes. In the vitellogenic stage, the oocytes accumulate vitellogenin, a yolk-precursor protein, by endocytosis in membrane limited yolk bodies. The maturation stage of oocytes includes the fusion of the yolk bodies, the nucleus migration toward the oocyte periphery and nuclear envelope breaks down