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Comparative study of life cycle ecology and host-parasite interactions of horsehair worms (phylum: Nematomorpha)

Anaya, Christina
For hundreds of years, the phylum Nematomorpha, commonly known as hairworms, has been the subject of rich and colorful folklore across the world. Many of these stories originated from characteristics such as their serpent-like shape, locations where they are found, and their ability to drive theirs hosts to water. Although we have gained significant knowledge in this understudied group, we are still in the infancy of understanding the diversity of species and their life cycles. For example, a recent study revealed that what was commonly known as Gordius robustus across North America, was a suite of eight genetically distinct species all of which were found to emerge between late spring and early fall. One exception to this were specimens collected from Texas, Louisiana, and Oklahoma. In chapter II, I describe this Gordius sp. based on my first-year collections in Oklahoma. These initial observation showed that hairworms were emerging from soil and congregating on lawns, sidewalks, and streets but seem to disappear within one or two days of rain drying out. But the most interesting find was the egg of this species which contained a double membrane, a trait not been observed in any hairworm species to date. In chapter III, I examined the natural history of this new Gordius species through a series of field and laboratory observations and experiments over a five-year period. I documented information on the habitat, seasonal occurrence, and infections of soil invertebrates as biodiversity indicators. In chapter IV, I expanded the principles of biodiversity indicators using aquatic snails as indicator hosts of hairworms across a large geographic region, Iceland. Finally, in chapter V, my objective was to expand our knowledge of host-parasite interactions in the phylum by examining survivorship and fecundity reduction in laboratory reared and infected crickets. Data presented in this dissertation provides a species description, a new life cycle strategy, a new documented species in Iceland, and new information that will change the perception of hairworms as parasitoids.