Exploring Parasite Diversity: Taxonomic Studies of Parasites from Birds, Crocodilians, and Anurans Across Diverse Ecosystems

Abstract

The overall objective of this dissertation was to apply modern taxonomic and molecular phylogenetic methods to understanding “hidden” (undiscovered) parasite diversity in common wildlife species. The specimens described herein were collectedly sourced from parasitological collections and expeditions in the Southeastern United States (Alabama, Louisiana, South Carolina, Georgia, Mississippi) as well as sub-Saharan Africa (Namibia, Mozambique, South Africa, Botswana). The Southeastern United States is a center of biodiversity for numerous aquatic invertebrate and vertebrate taxa, including mollusks that are the critical first intermediate host for nearly all lineages of trematodes (Platyhelminthes, Digenea; the focus parasite group of the dissertation). We think that the parasite groups infecting these diverse aquatic hosts are correspondingly diverse. Alabama is an ideal geographic locality to study the parasites of aquatic and semi-aquatic wildlife. Because, all free living organisms have some parasites, and despite many researchers writing big grants and traveling far from the United States to collect parasites, the parasites that infect American wildlife species remain under-sampled and under-explored. Sub-Saharan Africa is a renowned region of the world for its diversity of charismatic megafauna. It is less surveyed the parasites that infect them. This dissertation includes results from opportune necropsies of rarely examined water birds (white-backed and fulvous whistling ducks), which were infected by a new lineage (genus) of bird trematode, as well as an extremely fortunate opportunity to necropsy a fresh-killed Nile crocodile in cooperation with the Namibian Department of Conservation. Again, while the Nile crocodile is an iconic wildlife species in Africa, our examination of a single individual resulted in exciting parasitological discoveries.

Each chapter of this dissertation explores the taxonomic identity and phylogenetic interrelationships, and the Discussion sections and Taxonomic Remarks sections of the works detailed below include components of ecosystem health, ecosystem indicators, host health, biogeography, and host-parasite cophyly. For Chapter 1, In North America, we discovered Anativermis normdroneni n. gen., n. sp., in a Canada goose from Alabama—the first record of a cyclocoelid in this host and region. Cyclocoelids are trematodes (Cyclocoelidae) that primarily parasitize the air sacs and body cavities of birds, particularly waterfowl. Despite their presence in common bird species, many cyclocoelids remain inadequately studied, with new genera and species still being described, underscoring the need for further research. For Chapter 2, In Namibia, our survey of birds in ephemeral systems led to the first record of Dendritobilharzia pulverulenta in sub-Saharan Africa, infecting white-backed and fulvous whistling ducks. This also marked the first description of a female of D. pulverulenta from the continent where it was originally described. For Chapter 3, Similarly, we found Dracovermis occidentalis, an elusive liolopid digenean, in an American alligator from Alabama after nearly half a century without mention of the species. American alligators are charismatic megafauna that have been extensively studied, making the discovery of this seldom-found trematode quite surprising. For Chapter 4, In Africa, we discovered Ngubuvangandu francoisjacobsi n. gen., n. sp., in a Nile crocodile in Namibia, expanding our knowledge of crocodilian liolopids and reshaping their taxonomic grouping. This discovery underscores how much remains to be understood about crocodilian parasitology, even in species that are frequently examined, and emphasizes the need for ongoing exploration in well-studied wildlife populations. For Chapter 5, Furthermore, we identified Latergator louisdupreezi n. gen., n. sp., infecting the eye of an alligator in Louisiana. The discovery of a polystomatid on an alligator is significant, as it represents the first record of a polystomatid infecting a crocodilian. This broadens our understanding of the host range of these parasites and provides new insights into parasitic relationships in reptiles. For Chapter 6, In amphibians, we redescribed Polystoma nearcticum from Cope’s gray treefrogs in Alabama, with molecular data suggesting the need for a new genus to accommodate North American treefrog polystomatids. These discoveries, while occurring in different regions and hosts, share common themes: overlooked parasite diversity, host-parasite relationships that exceed geographic boundaries, and the continued need for taxonomic and molecular research to classify these organisms accurately. The fact that these parasites remained undiscovered or need to be redescribed in frequently studied animals highlights how much remains to be learned about parasite biodiversity, even in well-surveyed ecosystems. These findings underscore the vast, hidden world of parasites that remains to be explored, regardless of location.