Isolating and Characterizing the C. sp. 34 Dauer Larva
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Date
2017
Authors
Hammerschmith, Eric William
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Understanding the evolution of host seeking behavior is crucial to conceptualizing the evolutionary rise of parasitism and for the formulation of future treatments. Over a billion people are infected by parasitic nematodes, worms, globally. Amazingly, parasitic and non-parasitic nematodes have nearly identical pathways for developing the stress-resistant, dauer or infective, dispersal stages of their life cycles. One of the key divergent traits seen between infective and free-living is host specificity. The model organism Caenorhabditis elegans is promiscuous in it choice of transportation vector. Caenorhabditis species 34, a close relative of C. elegans, may represent a divergent phenotypic group of free-living worms with only one animal transportation vector. Using SDS to isolate dauers, C. elegans and C. briggsae were found to have higher dauer formation than C. sp. 34. When SDS was performed on 29 wild isolates of C. sp. 34, dauer frequency was again found to be lower than the other species, but variation in propensity to make dauers was seen in C. sp. 34. The C. sp. 34 dauer is significantly smaller than any other dauer measured and lacks the typical radial constriction found in dauers. However, it retains the classic dauer characteristic of pharyngeal constriction. Its unique dauer morphotype may be explained by the small size of its symbiotic partner, Ceratosolen. Additionally, conventional RNAi techniques using feeding to target dauer arrest genes failed to produce high amounts of dauers, but controls question the interoperability of the results. Fig plates were also generated as an alternative method to produce more dauers. Strangely, fig plates promoted nematode sterility and death. The unique dauer seen in C. sp. 34 may be evidence that the specificity of this species to its symbiont has played a large role in causing the divergent traits observed and open a promising door to possibly uncovering more about the evolution of host-specificity with future research.
Description
74 pages. A thesis presented to the Department of Biology and the Clark Honors College of the University of Oregon in partial fulfillment of the requirements for degree of Bachelor of Science, Spring 2017
Keywords
Caenorhabditis, Evolution, Dauer, Parasitism, Ecology, Morphology