Hopkins Marine Station Student Paper

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Title: Identification of suspected Carnobacteria sp. isolated from the brains of beached Salmon sharks (Lamna ditropis).
Student Author(s): Schaffer, Paula
Faculty Advisor(s): Palumbi, Stephen
Pages: 18
Location: Final Papers Biology 199H
Date: June 2004
Abstract: Juvenile salmon sharks beach yearly along the California coast during late summer and early fall. To determine the epidemiological condition of beached animals, frozen and formalin fixed beached specimens were collected from various Fish and Game facilities for examination and freshly beached specimens were also examined when possible. Histology revealed meningoencephalitis with intralesional bacteria in almost all of the specimens, including the freshly beached sharks, suggesting that this infection plays a role in this unusual behavior. The pathogenic bacteria was cultured from four separate shark specimens, and each isolate was characterized serologically and biochemically as belonging to the genus Carnobacteria. In order to identify the species, we sequenced ~540 bp of the 16s ribosomal DNA and a similarly sized portion of the large ribosomal DNA intergenic spacer (ITS or ISR). The 16s sequences obtained from all samples were identical and 99% similar to C. piscicola. The ISR sequences obtained from all samples were also identical to each other, but were only 92% homologous to C. piscicola, and did not match closely with any other sequence in GenBank. This is the first report of Carnobacterium infection in any shark species, though the identity of the pathogenic bacteria remains uncertain.