Description of Perkinsus andrewsi n. sp isolated from the baltic clam (Macoma balthica) by characterization of the ribosomal RNA locus, and development of a species-specific PCR-based diagnostic assay

A Perkinsus species was isolated from the baltic clam Macoma balthica and a n in vitro culture established under conditions described for P. marinus. A s reported previously, morphological features remarkable enough to clearly indicate that this isolate is a distinct Perkinsus species were lacking. In this study, regions of the rRNA locus (NTS, 18S, ITS1, 5.8S, and ITS2) of this isolate were cloned, sequenced, and compared by alignment with those a vailable for other Perkinsus species and isolates. Sequence data from the r RNA locus and species-specific PCR assays indicated not only that Perkinsus sp. from M. balthica was not P. marinus, but it was different from P. atla nticus and P. olseni. The degree of difference was comparable to or greater than differences between accepted Pr Perkinsus species. In particular, NTS sequence and length were dramatically different From that of P. marinus an d P. atlanticus. Therefore. we formally propose to designate the Perkinsus sp. from M. balthica as a separate species. P. andrewsi n. sp. Primers base d on P. andrewsi NTS sequence were used to develop a PCR-based diagnostic a ssay that was validated for species-specificity and sensitivity. PCR-based assays specific for either P. andrewsi or P. marinus were used to test for their presence in bivalve species sympatric to M. balthica. Although isolat ed from M. balthica. P. andrewsi was also detected in the oyster Crassostre a virginica and clams Macoma mitchelli and Mercenaria mercenaria, and could coexist with P. marinus in all four bivalve species tested.