Hatching in zebrafish (Danio rerio) embryos exposed to a 50 Hz magnetic field

Zebrafish embryos were exposed intra ovo to a 50 Hz AC magnetic field of 1000 microT rms, and the progress of asynchronous hatching was monitored. A statistically significant delay was observed when field exposure started 48 h after fertilization. In contrast, when exposure started 2 h after fertilization, no statistically significant effect was seen. When field exposure was administered together with submaximal doses of progesterone at 48 h postfertilization, the two treatments appeared to delay hatching in an additive manner. Evaluating the progress of hatching in zebrafish embryos seems relevant for exploration of EMF effects on reproduction.