Egg morphology, dispersal, and transmission in acanthocephalan parasites: integrating phylogenetic and ecological approaches
Date of Award
Master of Science (MS)
Timothy Sparkes, PhD
Stan Cohn, PhD
Windsor Aguirre, PhD
Acanthocephalans are endoparasites that infect arthropods as intermediate hosts and vertebrates as definitive hosts and are found in diverse habitats (freshwater, marine, terrestrial) throughout the world. Free-living eggs are expelled from the definitive host into the environment, which are then consumed by an intermediate host. Once ingested by the intermediate host the parasite undergoes a series of developmental stages, the final stage is infectious to the definitive host. Transmission to a definitive host occurs when the predator consumes an intermediate host containing an infectious parasite. The parasites reach sexual maturity within the definitive host. Most research to date has focused on parasite transmission from the intermediate to definitive hosts. Here, I examined egg morphology, dispersal, and transmission of the free-living stage of acanthocephalan parasites using phylogenetic and ecological approaches. I assessed variation in multiple aspects of acanthocephalan egg morphology, specifically shape and size, and demonstrated that these traits exhibit significant variation among and within classes. I also studied the evolution of egg fibrils within the Acanthocephala using the comparative method, and demonstrated that fibrils are likely homoplasies due to convergent evolution. Finally, I used laboratory experiments to examine factors associated with transmission of the acanthocephalan parasite Acanthocephalus dirus to its intermediate host Caecidotea intermedius and demonstrated that the presence of egg fibrils appears to favor transmission to the intermediate host through multiple routes.
Pfenning, Alana C., "Egg morphology, dispersal, and transmission in acanthocephalan parasites: integrating phylogenetic and ecological approaches" (2017). College of Science and Health Theses and Dissertations. 272.