Evolutionary toxicology of the invasive eastern mosquitofish (Gambusia holbrooki) in Azerbaijan

Brian P Rinner, Purdue University

Abstract

Nucleotide sequences of the control region of the mitochondrial DNA of invasive mosquitofish from the highly contaminated industrial city of Sumgayit, Azerbaijan were compared to invasive mosquitofish from pristine sites in Europe and Azerbaijan and to native North American populations. All European and Azerbaijan fish had haplotypes indicative of Gambusia holbrooki which is native to the eastern United States. Persistent heteroplasmy for a hyper-mutable simple sequence repeat was observed in all invasive populations, as well as low haplotype and nucleotide diversities. However, the city of Sumgayit was unique in possessing four de novo haplotypes and heteroplasmic conditions, only one of which was found in a nearby population. It is concluded that Sumgayit is a mutational hotspot and the cause of the mutations are exposure to legacy contaminants from chemical factories that were mainly operating during the era of the Soviet Union. Sumgayit was also observed to be the site of new mutations in a previous study of marsh frogs (Rana ridibunda), but it is not an ecological sink for mosquitofish as was the case with marsh frogs. All of the observed variable nucleotide positions were located within or adjacent to a cytosine mononucleotide repeat. This repeat was predicted to be within a conserved secondary structure in both G. affinis and G. holbrooki and it is concluded that this region undergoes expansion and contraction at a rate sufficient to prevent fixation of the common 1-3 heteroplasmy. Whereas the 1-3 heteroplasmy appeared coincident with the establishment of mosquitofish in Europe, the other forms of heteroplasmy result from contaminant-induced de novo mutations. Native populations of both species of mosquitofish possess the mononucleotide repeat but lack the persistent heteroplasmy. This study builds on a long-term program that has shown Sumgayit to contain ponds and wetlands with high levels of a diversity of chemical contaminants including mercury, PAHs, organochlorine pesticides and PCBs. Previous contaminant and biomarker studies of turtles (Emys orbicularis and Mauremys caspica) and marsh frogs have shown a correlation between somatic chromosomal damage and chemical contaminants. This study shows that an invasive species which arrived in Azerbaijan about the time of the establishment of the industrial city of Sumgayit has a pattern of genetic impacts similar to a native species taken from the same ponds. This confirms that the pattern is not the result of historical events such as glacial cycles, but is rather associated with recent chemical contamination.

Degree

M.S.

Advisors

Bickham, Purdue University.

Subject Area

Forestry

COinS