Date of Graduation

Fall 2015


Master of Science in Biology



Committee Chair

M. Chris Barnhart


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.


Unionida, mussel, Venustaconcha pleasii, mitochondria, sperm

Subject Categories



© Amy Louise Maynard

Open Access

Included in

Biology Commons