A Method for Karyotyping Zebrafish Oocytes.

In this study, zebrafish follicles containing stage III oocytes were isolated and incubated in vitro to allow oocyte maturation. A minicell containing the intact oocyte spindle was excised after proteolytic digestion of the micropyle area of the follicle. The minicell was subjected to hypotonic treatment in deionized water for 10 min, and then spread on glass slide for karyotyping. Dyads at metaphase II and sister chromatids at anaphase II are clearly shown. Also, cytochalasin B treatment inhibited chromosomal segregation. This simple and inexpensive chromosome preparation protocol could be readily applicable to other fish species.