Taxonomy and Systematics of Early Lineage Fish Blood Flukes (Digenea: Aporocotylidae)
Type of DegreeMaster's Thesis
DepartmentFisheries and Allied Aquacultures
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The monophyletic fish blood flukes (Platyhelminthes: Digenea: Aporocotylidae Odhner, 1912) comprise ~166 species assigned to 40 genera infecting freshwater, marine, and estuarine fishes. They are occasional pathogens of cultured fishes, and are ancestral to the paraphyletic turtle blood flukes (“Spirorchiidae”) and the human-pathogenic blood flukes (Schistosomatidae Stiles and Hassal, 1898). The life cycles of aporocotylids include a mollusk or polychaete intermediate host (wherein the parasite undergoes clonal asexual reproduction) and a fish definitive host (wherein the parasite matures). Cartilaginous fishes are rarely examined for aporocotylids, and prior to my work, only seven species were described. Blood flukes described in this thesis were collected from 329 fish assigned to four genera in four families as well as from 1,185 bivalves from two families. I use alpha taxonomy, scanning electron microscopy (SEM), genetic sequence techniques (PCR; large subunit ribosomal DNA [28S], small subunit ribosomal DNA [18S], and internal transcribed spacer 2 [ITS2]), and molecular phylogenetic analysis (Baysian inference) to characterize four new species assigned to three new genera. I describe Acipensericola glacialis n. sp. from the heart of the lake sturgeon, Acipenser fulvescens, Gymnurahemecus bulbosus n. gen., n. sp. from the heart of the smooth butterfly ray, Gymnura micrura, Electrovermis zappum n. gen., n. sp. from the heart of the lesser electric ray, Narcine bancroftii, and a new genus and species from the heart of the smalltooth sawfish, Pristis pectinata). Further, I elucidate the life cycle of E. zappum, characterize a new cercaria infecting the green jackknife clam, Solen viridis, and compare all aporocotylid cercariae that infect marine and estuarine gastropods, bivalves, and polychaetes. This work culminates in the first descriptions of blood flukes infecting the order Torpediniformes, the families Acipenseridae, Gymnuridae, and Pristidae, as well as the first elucidated blood fluke life cycle that includes a chondrichthyan definitive host and a bivalve intermediate host. Further, I provide the 2nd genetic sequence from a blood fluke infecting an acipenseriform, and the 3rd and 4th genetic sequences from blood flukes infecting chondrichthyans, as well as the 2nd and 3rd sequences from cercariae infecting bivalves. This work has resulted in publications in Systematic Parasitology, Parasitology Research, and International Journal for Parasitology: Parasites and Wildlife.