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 10 00 mu T rms, and the progress of asynchronous hatching was monitored. A sta tistically significant delay was observed when field exposure started 48 h after fertilization. In contrast, when exposure started 2 h after fertiliza tion, no statistically significant effect was seen. When field exposure was administered together with submaximal doses of progesterone at 48 h postfe rtilization, the two treatments appeared to delay hatching in an additive m anner. Evaluating the progress of hatching in zebrafish embryos seems relev ant for exploration of EMF effects on reproduction. (C) 2000 Wiley-Liss, In c.