Biology Projects 2008

Investigation of cutaneous bacterial species diversity and its antifungal properties on different populations of Rana catesbeiana

Project Mentor - Kathy Szick-Miranda, Antje Lauer

Invasive species such as the North American bullfrog (Rana catesbeiana) are successful breeders in a variety of environments. They are outcompeting native amphibian species due to various reasons. One reason that explains their success is that they are immune to a variety of amphibian diseases including Chydridiomycosis. Chydridiomycosis in amphibians is caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), and results in the destruction of the keratin layer of the skin. This disease is responsible for major amphibian declines worldwide, in areas where habitat destruction and pesticides play a major role. The reason why R. catesbeiana is not succumbing to Bd infections is not known. The objectives of the summer research project were to isolate residential cutaneous bacteria from the skin of R. catesbeiana from different populations and test them for antibiotic production in challenge assays against Bd and an unknown fungus that was isolated from the skin of one amphibian on nutrient agar plates and to compare the associated cutaneous bacterial communities by a combined approach of Polymerase Chain Reaction (PCR) and subsequent Denaturant Gel Electrophoresis (DGGE) of 16SrRNA gene fragments. We have discovered and swabbed 32 individual R. catesbeiana individuals at five different locations in Bakersfield and also in the foothills of the Sierra Nevada. Beside of R. catesbeiana we also included other amphibian species (Bufo boreas halophilus [17 individuals] and Pseudacris regilla [18 individuals]) and R. catesbeiana tadpoles (17 individuals) in this study for comparison reasons. This project will contribute to the global search for a plausible solution to combat Chydridiomycosis that can be applied in nature without concern. Furthermore, this study also identifies the cutaneous bacterial diversity of an invasive amphibian species that is resistant to many microbial pathogens including Bd.

This project resulted in two posters that summarize the work, poster 1 and poster 2.

Cannibalism and Scorpion Mating Under UV Light.

Faculty Mentor - Carl Kloock

We tested the hypothesis that Fluorescence effects mating and Cannibalism in scorpions by staging mating trials under three different lighting conditions: blacklight (producing fluorescence), UV-blocked blacklight (preventing most fluorescence), and no light (preventing all fluorescence). Probability of forming a spermatophore was not effected by lighting conditions, but there were significantly more instances of cannibalism under the no-light treatment than under the two conditions with light available.

Conservation Genetics and Phylogenetics of Kangaroo Rats (Dipodomys) (Rodentia: Heteromyidae)

Faculty Mentor - Paul Smith

Genetic analyses of Kangaroo Rats, genus Dipodomys, were undertaken using DNA sequence analysis of two mitochondrial genes. First, we compared three geographically separated populations of the Giant Kangaroo Rat (D. ingens) and found no evidence of gene flow between the Panoche (San Benito, Co.) and Lokern (Kern Co.) populations, but there is evidence of gene flow between the Carrizo and Lokern populations. We also detected a surprising amount of genetic diversity within the Panoche and Lokern populations. Phylogenetic analysis of mitochondrial cytochrome oxidase b gene sequences suggested that: (1) Dipodomys is monophyletic and (2) the following species groups were each recovered as monophyletic lineages: D. heermani group, D. agilis group, D. spectabilis group, and D. phillipsii group; however, the relationships of the species groups to each other could not be fully resolved. Finally, the genetic differences (~10%) exhibited between the two populations of D. ingens suggest that they may be different subspecies.