The Zebrafish in Toxicology/Ovary staging

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Reproduction - Ovary[edit]

Normal Histology[edit]

ovary development[edit]

previtellogenic stageing: sequential images

previtellogenic stageing: sequential images
Six subsequent previtellogenic (intermediate) stages of ovary maturation, as recorded in juvenile zebrafish 6 weeks of age, and classified according to the most predominant oocyte maturation stage.
For structure analysis of these images, see structure - immature.

An example of the application of this classification is the evaluation of the effects of effluent of a sewage treatment works (Eindhoven, the Netherlands) in zebrafish, shown at the bottom of this page.


Coronal section of a juvenile female zebrafish, age 6w; H&E staining (all images)

stage 0

undifferentiated gonad


stage 0-1

appearance of stage 1 primary oocytes (previtellogenic, small rim of cytoplasm)


stage 1

predominance of stage 1 primary oocytes


stage 1-2

intermediate stage, mixed occurence of stage 1 and stage 2 primary oocytes


stage 2

initial growth of oocytes: increase of nucleus size, increase of cytoplasm volume, cytoplasm becomes basophilic


stage 3

appearance of stage 3 oocytes (further increase of cytoplasm to approx. 100 µm cell diameter, bright spotting in the cytoplasm as indication of endogenic vitellogenin accumulation)


Application of the ovary maturation classification in the evaluation of the effects of effluent of a sewage treatment works (Eindhoven, the Netherlands) in zebrafish. Adult zebrafish and their progeny were exposed to either control Dutch Standard Water (DSW ¾-, blue line ), estradiol (E2, ¾-, red line ), or sewage effluent ( ¾-, magenta line ) for 6 weeks. Shown is the average of the percentages of the total number of animals in the respective groups (2-5 groups per treatment, 30-50 individuals per group) in each class.

It appeared that exposure of juveniles to either E2 or sewage effluent inhibited ovary maturation, compared to control animals