Ovarian follicle dynamics assessed in vivo by intraperitoneal (I.P.) trypan blue uptake during Vitellogenin endocytosis in adult female zebrafish (Danio rerio)

The timeline of zebrafish follicle-enclosed oocyte growth and development is not known. To establish the temporal stages of these basic processes, mature female zebrafish, Danio rerio, were injected intraperitoneally (i.p.) with the marker trypan blue (TB). Ovaries were removed at different times post injection. Then, oocyte diameter and TB uptake were determined from brightfield and fluorescence microscopy images, respectively. TB uptake increased steadily up to 48 hours post injection and declined subsequently. TB fluorescence was highest in the vitellogenic stage III follicles (i.e. 350 - 600 μm in diameter). TB is known to fluoresce when bound to proteins such as serum albumin and the data presented here indicated labeling of serum vitellogenin that subsequently was endocytosed into yolk vesicles of vitellogenic stage oocytes. Overall, this chapter provides an initial study of oocyte growth and development using TB as a cellular marker