Date of Award

Spring 5-2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Chair

Dr. Robin M. Overstreet

Committee Chair Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 2

Dr. Richard W. Heard Jr.

Committee Member 2 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 3

Dr. Jeffrey Lotz

Committee Member 3 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 4

Dr. William Font

Abstract

“Fish blood flukes” (Digenea: Aporocotylidae) comprise an ancient and taxonomically diverse group o f flukes that infect an array o f distantly-related, non-tetrapod craniate lineages. The foundation of this dissertation comprises dissections of >2,500 fish of >200 species in 122 genera, 67 families, and 20 orders from marine and estuarine systems in the Northwestern and Eastern Atlantic Ocean, Eastern and Western Pacific Ocean, Sea o f Cortez, G ulf o f Mexico, Caribbean Sea, and Mediterranean Sea as well as from lakes and rivers in North America, South America, and Africa. An overview o f the biological interactions between digeneans and their fish hosts indicates that digeneans exhibit marked phylogenetic and ecological specificity to particular hosts and that those host-parasite relationships have matured along a geologic timescale. Aporocotylidae is identified as a suitable group within which to study parasite-host evolution because o f the phylogenetic diversity o f their hosts and because of their basal position in Trematoda. I provide an updated diagnosis for Aporocotylidae, emend each generic diagnosis, confirm the generic identity o f each accepted species, describe 12 new species and propose 9 new genera, and establish the host and geographic range for species and genera by identifying dubious host records and applying correct taxonomic names to each reported host species. This work culminates in the first clade-based phylogenetic hypothesis for Aporocotylidae. A strict consensus o f the 22 most parsimonious trees generated from an analysis o f 204 unordered, unweighted morphological characters and 36 taxa yielded a tree topology in which the fish blood flukes can be divided into “blood flukes o f...” chimaeras + sharks, basal actinopterygiians + elopomorphs, otophysans, and euteleosts. Parsimony analysis o f the 18S small subunit ribosomal DNA produced a single most parsimonious tree that supported the morphology-based tree topology. The analyses together suggest that 1) phylogenetic host specificity among aporocotylids is structured at the level o f higher order craniate subdivisions, 2) primitive vertebrate lineages harbor primitive aporocotylids, 3) highly-derived aporocotylids infect Euteleostei, 4) most basal aporocotylids infect freshwater fishes, and 6) host switching events involve euryhaline fishes acquiring freshwater blood flukes.

Download

Share

COinS