Date of Award

Summer 8-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean Science and Technology

Committee Chair

Robert Joseph Griffitt

Committee Chair Department

Ocean Science and Technology

Committee Member 2

Richard Heard

Committee Member 2 Department

Ocean Science and Technology

Committee Member 3

Michael Zachary Darnell

Committee Member 3 Department

Ocean Science and Technology

Committee Member 4

Anindo Choudhury

Abstract

The Opecoelidae Ozaki, 1925 is one of the largest families of digenetic trematodes of fishes. While the family is mostly marine/estuarine, invasion of freshwater hosts has occurred at least two times. The only representative freshwater plagioporine sequenced to date is Plagiocirrus loboides Curran, Overstreet, & Tkach, 2007, which previous phylogenetic analyses resolved as being related to deep water marine opecoelids. The taxonomy of the freshwater plagioporines, particularly Plagioporus, has long been confused; homoplasy is rife within the family and has complicated the delineation of species and genera, and the freshwater species from marine forms. Here, I hypothesize that the freshwater plagioporines, including Plagioporus, form a monophyletic group and that intestinal Plagioporus have radiated across many families of freshwater/anadromous fish and within several, particularly for the cyprinids, percids and catostomids. I describe 10 new species and 2 new forms of Plagioporus from North America, and redescribe 3 congeners. I obtained sequences of the ITS1+2 and 28S rDNA gene regions of these new species and forms, 5 previously described congeners from the Nearctic and also from 5 species of Neoplagioporus and Urorchis from Japan. Bayesian inference analysis of 28S and 28S concatenated with ITS2 revealed that the freshwater plagioporines form a monophyletic group, with species from the Nearctic resolved as sister to those from the Palearctic with high support. Plagiocirrus loboides was nested within the clade composed of members of Plagioporus and was therefore transferred to Plagioporus. Plagioporus was amended to accommodate a posteriorly extending uterus and restricted vitelline field, two characters that were also shown to be problematic in distinguishing Urorchis from Neoplagioporus. Plagioporus was further amended to accommodate 2 species from Arkansas with long excretory vesicles. Nearctic Plagioporus now comprise a monophyletic group with species from cyprinid, catostomid, percid, salmonid, gasterosteid, fundulid, ictalurid and cottid definitive hosts. In addition, morphological and molecular data suggest that monophyletic radiations of intestinal Plagioporus have occurred within the percids, cyprinids and catostomids. With 23 species, Plagioporus is now the most diverse digenean genus of fish trematodes in the Nearctic and one of the most successful in terms of its radiation across fish host families.

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