Sea Lamprey (image) Marine Biological Laboratory Caption The sea lamprey (Petromyzon marinus) is an aggressive parasite that is considered a pest in many regions, including the US Great Lakes. An ancient vertebrate, its lineage diverged from that of humans about 500 million years ago. The lamprey is now our earliest vertebrate ancestor to have its whole genome sequenced and assembled. Credit New York State Department of Environmental Conservation. Usage Restrictions Please use with proper credit. 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.