The phenotypic and behavioral correlates of mitochondrial variation in three-spined stickleback (Gasterosteus aculeatus)
Publication Date
July 27, 2026
Creator
Shepherd, Emma
University of Nottingham School of Life Sciences
Abstract
Life-history theory provides a unique framework for understanding the characteristics of an organism that makes them successful in life. Life-history traits such as growth and reproduction are influenced by mitochondrial DNA (mtDNA), making this organelle an interesting study topic within life-history theory. While the effects of mtDNA can be isolated and identified in a laboratory setting through conplastic experiments, identifying what mtDNA influences in the wild is much harder due to the rarity of a naturally-occurring well-mixed nuclear genomic background. This study proposes the three-spined stickleback on North Uist, Scotland to be an ideal wild organism for mitochondrial studies, as their populations exhibit a well-mixed nuclear genome, but two separate mitochondrial haplotypes (trans-Atlantic and European). One-hundred and eighty migratory three-spined stickleback were sampled from six saltwater lochs on North Uist to determine the extent to which mtDNA impacts phenotypic traits like organ size, body size, and ovule volume/clutch size, as well as metabolic traits like citrate synthase enzyme activity. Interestingly, results showed that stickleback haplotype influenced citrate synthase enzyme activity and male gonadosomatic index (GSI), as the European haplotype exhibited both more enzyme activity and a higher male GSI. While potentially a result of one or more factors, differences in citrate synthase levels could indicate the Eu haplotype as being better at biosynthesis or potentially having more mitochondria. Differences in male GSI may be explained by the timing of male spermatogenesis or potentially the need for larger testes in Eu fish. While no other phenotypic trait showed differences between mitochondrial haplotypes, there were many differences that emerged between sexes and between populations such as body size and organ/muscle size. This study provides a holistic look at the relationship between mitochondria, sex, and population in North Uist’s migratory three-spined stickleback populations and serves as a good starting point for further research in this topic.
Item Type
ethesis
Thesis Type
MRes
Supervisors
Maccoll, Andrew
University of Nottingham
Goodacre Sara L.
University of Nottingham
Subjects (LC)
Associated Schools / Departments
UoN Repository URI
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