Date of Graduation
Master of Science in Biology
M. Chris Barnhart
Unionida, mussel, Venustaconcha pleasii, mitochondria, sperm
Gonochoristic species of the bivalve order Unionida possess two types of mitochondria. The female-inherited mitochondria (F-mt) is found in the somatic cells of both sexes, while male-inherited mitochondria (M-mt) is found in the male gonad. These mitochondria possess different open reading frames (M-ORF or F-ORF respectively). Previous studies suggested that two types of sperm might exist, each carrying one or the other mitochondrial haplotype, and it was hypothesized that the presence of either F-mt or M-mt in sperm may be involved in determination of offspring sex. I investigated this hypothesis in Bleedingtooth (Venustaconcha pleasii). Sperm samples were obtained from field-collected males that spawned spontaneously in the lab. M-ORF and F-ORF mitochondrial DNA were cloned and sequenced, and PCR was used to test for the presence of M-ORF and F-ORF genes within spermatozoa. F-ORF was not detected within sperm of V. pleasii despite previous reports of the protein product of F-ORF within sperm of V.ellipsiformis. M-ORF was present within sperm and more than one haplotype of this gene appeared to exist within an individual mussel. M-ORF and F-ORF evolve rapidly and may be useful for phylogenetic comparisons. Comparisons with V. ellipsiformis showed 82.6% (M-ORF) and 76.1% (F-ORF) sequence homology. Comparison of F-ORF and M-ORF in V. pleasii display low sequence homology (20.6%). My results indicate that sperm only deliver the M-mt haplotype and therefore, that sex determination must involve mechanisms other than sperm mtDNA haplotype.
© Amy Louise Maynard
Maynard, Amy Louise, "Sex-Associated Mitochondrial Genes: Tools For Understanding Unionid Reproduction and Development" (2015). MSU Graduate Theses. 974.