The effects of different intensities of static magnetic fields on ovarian tissue in Zebrafish (Danio rerio)

The aim of this study was to a histological investigation of zebrafish ovary and the process of ovulation under the effect of various intensities of the static electromagnetic field. 80 adult female fishes with an average weight of 0.4-0.7 g were selected and exposed to different intensities of electromagnetic field (2.5، 5 and 7.5 mT) for one hour per day for 7 days. On the 7th day, the ovaries were removed, after fixation and embedding; tissue sections were prepared with a thickness of 5 microns. The results showed that during the development of oocytes, six phases are observed. Comparison of the effects of different doses of the static electromagnetic fields on ovarian tissue of zebrafish showed that oocytes enter the atresia phase at intensities of 7.5 mT. These oocytes will not have normal fertilization if they are released. At low intensities of electromagnetic field (2.5 and 5 mT), most oocytes are observed in cortical alveolar phases, vitellogenesis, and mature phases. The percentage of atretic oocytes is low, and the rest of the oocytes will have normal fertilization. In conclusion, it seems that high-intensities of the static electromagnetic field have negative effects on the reproduction of zebrafish and could reduce their regeneration.