Stage of a Parasite Larva (IMAGE) University of California - Santa Barbara Caption This free-swimming stage of a parasite larva, a trematode cercaria, leaves an infected snail to encyst on a fish brain. View is 0.267 mm across. Credit Courtesy Todd Huspeni, University of California, Santa Barbara 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.