Sea Lamprey (IMAGE) U.S. Geological Survey Caption USGS sea lamprey expert Nick Johnson demonstrates the ridge of tissue, called a rope, along the back of a mature male sea lamprey. Credit Andrea Miehls, USGS 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.