Zebrafish (IMAGE) Institute of Science and Technology Austria Caption Zebrafish (Danio rerio) are a great model organism for studying early embryo development, as their embryos are transparent and develop quickly. Crucial steps can be seen within 24 to 48 hours of fertilization. Credit Nadine Poncioni/ISTA Usage Restrictions - License Original 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.