Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 1999
Publication Date: N/A
Interpretive Summary: There is increasing concern over the integrity and the biodiversity of the Atlantic Coast and the Chesapeake Bay habitats following the collapse of the Eastern Shore fisheries. Decline in the Eastern Shore oyster industry is attributed to infection of the protozoan, Perkensis marinus. Although these parasites have been identified in 60 different species of molluscs, little is known about their diversity and speciation, their pathogenicity, and their host specificity. Identification of the parasites traditionally has been based on morphology and biochemical phenotypes. From our study we conclude that softshell clams in the Chesapeake Bay may be infected by multiple genotypes of the oyster parasite, Perkensis. Also, we demonstrated that at least two different species of Perkensis can coexist in an infected mollusc. This information is useful to scientists working to protect the oyster industry.
The internal transcribe spacer (ITS-1 and ITS-2) regions and the 5.8S ribosomal RNA gene of 2 Perkensis spp. (G117 and H49) originating from the softshell clam, Mya arenaria, of the Chesapeake Bay were cloned and sequenced to obtain evidence for genetic divergence. A high level of heterogeneity in both regions, probably resulting from deletions, insertions, and base substitutions, was evident from alignments of the sequences of the 2 isolates with published sequences of other Perkensis spp. The isolate G117 and other Perkensis spp. were highly divergent (13-26% and 19-20% sequence divergence in ITS-1 and ITS-2, respectively). Evidence obtained from the phylogenetic analysis using the aligned sequences suggests that G117 and H49 belong to two distinct species of Perkensis. The isolate G117 possibly belongs to an as yet undescribed species of Perkensis and H49 belongs to the species P. marina. The conclusions drawn from the genetic analysis of H49 and G117 are supported by previously reported morphological characteristics (McLaughlin & Faisal, 1998b). Isolates H49 and G117 originated from the same molluscan species demonstrating that at least 2 different species of Perkensis can co-exist in 1 host.