A comparison of a normally developed Atlantic killifish embryo, left, and an embryo affected by a group of chemicals called PCBs. The fish on the right has a deformed heart. Killifish that have ...

Fundulus heteroclitus, the Atlantic killifish. This material relates to a paper that appeared in the Dec. 9, 2016, issue of Science, published by AAAS. The paper, by N.M. Reid at University of ...