Date of Completion

5-4-2018

Embargo Period

5-3-2018

Keywords

Echeneibothriidae, Rajiformes, Parasitology, elasmobranch cestodes, Rajiformes, Host-Parasite systems, Taxonomy, Systematics, Phylogenetics, Cophylogeny, Cestoda

Major Advisor

Janine N. Caira

Associate Advisor

Bernard Goffinet

Associate Advisor

Elizabeth L. Jockusch

Associate Advisor

Paul O. Lewis

Field of Study

Ecology and Evolutionary Biology

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Members of the rhinebothriidean family Echeneibothriidae de Beauchamp, 1905, parasitize skates exclusively and represent one of the most diverse elements of their cestode fauna. Although skates represent one of the most speciose orders of elasmobranchs, their superficial morphological homogeneity has led to a convoluted taxonomic history, hindering studies of their parasites. Recent advances in the taxonomy and systematics of skates allow for more informed assessments of the diversity, distributions, and patterns of host associations of skate cestodes. Most of the 35 species of echeneibothriids known prior to this study occur in skates distributed in the northern hemisphere, despite the fact that the number of skate species is comparable in both hemispheres. Examination of the spiral intestine of 24 species of skates, 17 from the southern hemisphere, resulted in the recognition of 42 species of echeneibothriids, 32 of these new to science. The amount of novelty recovered prompted the development of a template for the description of new species in the family that conform to the standards now commonly practiced in the description of cestodes from elasmobranchs. An account of the cestode fauna found in each of the skate species examined is provided. Species of echeneibothriids were morphologically circumscribed using a combination of characters of their scoleces. Global diversity of echeneibothriids is estimated to be 376 species. Descriptions for two new species of Echeneibothrium are also provided. Molecular characterization of all species for which suitable material was available is given. Data from two molecular markers, the D1–D3 regions of 28S rDNA and ITS-1, were obtained and used to infer a phylogeny for the family Echeneibothriidae. The monophyly of the family is confirmed but the two most speciose echeneibothriid genera, Echeneibothrium and Pseudanthobothrium, are not monophyletic as currently circumscribed. Of the 14 skate species examined, 12 hosted more than one species of echeneibothriid. In most cases, congeners parasitizing the same skate species were found to not be each other’s closest relatives. Cophylogenetic analyses using different methods yielded conflicting results, suggesting that the host association patterns we observe in cestodes of skates may be the result of aspects other than cophylogeny alone.

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