SHEDDING OF UNTRANSFORMED GLOCHIDIA BY FISHES PARASITIZED BY LAMPSILIS-FASCIOLA RAFINESQUE, 1820 (MOLLUSCA, BIVALVIA, UNIONIDAE) - EVIDENCEOF ACQUIRED-IMMUNITY IN THE FIELD

Fifteen fish species were exposed to glochidia from the freshwater mus sel Lampsilis fasciola. Mussels and fishes were collected in the Big D arby Creek system in Ohio. All fishes began shedding untransformed glo chidia within 24 hrs of exposure and continued for approximately eight days. On Day 19, after two weeks of inactivity, rosefin shiner began to shed numerous untransformed glochidia again. This release lasted 24 days. Rainbow darter began shedding untransformed glochidia on Day 25 and continued to do so for 14 days. No transformation occurred on eit her fish species. We believe this reaction was due to an acquired immu nity and may represent the first report of this phenomenon in wild-cau ght fishes.