Least Killifish (IMAGE) University of Cincinnati Caption UC is using least killifish as a model organism to study the effects of hormones in drinking water. They are among the smallest vertebrates on Earth. Credit Andrew Higley/UC Creative Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.