Publication Date

12-2018

Date of Final Oral Examination (Defense)

4-24-2018

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Biology

Department

Biology

Major Advisor

Merlin M. White, Ph.D.

Advisor

Ian C. Robertson, Ph.D.

Advisor

Peter Koetsier, Ph.D.

Abstract

Presented is the first field survey and laboratory-based study focused on Harpellales gut fungi found in Culicidae (mosquito) larvae collected from various parts of Idaho. Overall, 34 sites were sampled ranging from urban storm drains and irrigation puddles to pristine stream-side puddles. These sites yielded 17 different species of mosquitoes and three previously described species of gut fungi. Three species of mosquitoes were the first recorded observations as hosts of the following gut fungi: Culiseta alaskaensis was infested with Zancudomyces culisetae (from Renwyck Creek), Culex tarsalis with Smittium culicis (from Cottonwood Creek), and Ochleratus sp. with Smittium minutisporum (from Bear Creek). Although unknown as to why, only one type of mosquito-borne fungus was found in each creek’s nearby lentic system. This finding warrants future investigation. Arid conditions throughout the state led to challenges in finding infested hosts. However, gut fungi were observed in larvae when their lentic sites had been directly connected with a stream system. Lentic systems free of any lotic association did not yield any gut fungal infestation. To test the susceptibility of isolated lentic sites, non-infested storm drain mosquitoes, Culex pipiens, were collected, inoculated, and colonized by Z. culisetae in the laboratory. The survey also yielded the first natural observation of both S. culicis and Z. culisetae as precocious midgut dwelling germlings found in Culicidae larvae. The germlings of both species were either simply attached to the surface or actively penetrating the midgut. When penetrating, each germling had distinct forms of attaching and anchoring during precocious development, which were different from a more typical “gluing” and non-penetrating holdfast attachment in the hindgut. These penetrations created openings in the midgut, which left mosquito larvae vulnerable to viral passage into the hemocoel. The possibility of germlings participating in vertical transmission of viruses into adult stages is discussed speculatively.

DOI

10.18122/td/1485/boisestate

Available for download on Saturday, December 19, 2020

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