Date of Award

Fall 10-8-2020

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Ocean Science and Engineering

Committee Chair

Robert Griffitt

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Robin Overstreet

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Zachary Darnell

Committee Member 3 School

Ocean Science and Engineering

Committee Member 4

Joseph H.K. Pechmann

Abstract

Infections of the protist parasite, Dermomycoides sp. are thought to have caused several years of low recruitment in the dusky gopher frog (Rana sevosa) populations. I evaluated the effects of density of the infective zoospores, host developmental stage, and tadpoles' ability to acquire resistance to Dermomycoides sp. on dusky gopher frog tadpoles. Tadpoles were exposed to zoospore densities of 0, 250, 500, and 750 zoospores/µL at Gosner stage 25, and we found no significant differences among treatments in tadpole mortality. In evaluating susceptibility by development stage, I exposed R. sevosa to 50 zoospores/µL as eggs, embryos, hatchlings, and 2-weeks post hatching tadpoles. Hatchlings (17 days, SE = 2.09 days) and tadpoles exposed 2-weeks post-hatching (17.65 days, SE = 1.48 days) had a significantly lower days to mortality than tadpoles exposed as eggs(27.56 days, SE = 2.09 days) or embryos ( 25.81 days, SE = 2.09 days). To assess if gopher frog tadpoles can acquire resistance to Dermomycoides sp. I exposed tadpoles around Gosner stage 25 to an initial zero (0 zoospores/µL), low (50 zoospores/µL), or high (250 zoospores/µL) dose of Dermomycoides sp. Two-weeks later each treatment was exposed to a second zero, low, or high dose for a total of 9 treatments. Survival was lowest in tadpoles that received a low initial dose followed by a zero or high challenge dose (0 and 3.03% respectively). I found that gopher frog tadpoles can acquire resistance to Dermomycoides sp., and that age at initial exposure plays an important role in tadpole survival.

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