MOLECULAR CHARACTERIZATION OF SPOROCYSTS AND CERCARIAE (DIGENEA: BUCEPHALIDAE) INFECTING THE EASTERN OYSTER CRASSOSTREA VIRGINICA FROM VIRGINIA

The identity of a larval bucephalid infecting the eastern oyster, Crassostrea virginica (Gmelin, 1791), from a tidal river in Virginia is investigated using ribosomal deoxyribonucleic acid (rDNA). The internal transcribed spacer (ITS1, 5.8S, ITS2) region and a portion of the 28S rDNA were isolated from genomic DNA from sporocysts containing cercariae and compared with sequences from GenBank and from our previous collections of possibly related bucephalids. The studied larval bucephalid was 100% identical at the ITS1, 5.8S, and partial 28S rDNA sequences with Prosorhynchoides paralichthydis (Corkum, 1961) Curran and Overstreet, 2009; however, it differed from P. paralichthydis by 6 bases plus 3 deletions in the ITS2 region. This level of variation at the ITS2 region has been demonstrated among some Indo-Pacific species of Prosorhynchoides Dollfus, 1929, suggesting that the larval bucephalid represents an unidentified or innominate species of Prosorhynchoides that is closely related to P. paralichthydis.