Trial Lecture
Title: "The role of sexual selection in shaping sperm morphology across vertebrates."
Time and place: August 28, 2025, 10:15 AM, Tøyen Hovedgård
Public Defence
Adjudication Committee
- Professor Jukka Kekäläinen, Department of Environmental and Biological Sciences, University of Eastern Finland, Finland
- Associate Professor Suvi Ruuskanen, Department of Biological and Environmental Science, University of Jyväskylä, Finland
- Professor Lee Hsiang Liow, Natural History Museum, University of Oslo
Chair of the Defence
- Research Director and Professor Hugo de Boer, Natural History Museum, University of Oslo
Supervisors
- Professor, Erica Helen Leder, Department of Marine Sciences, University of Gothenburg, Sweeden & Natural History Museum, University of Oslo
- Professor Arild Johnsen, Natural History Museum, University of Oslo
- Professor Michael Matschiner, The Ludwig Maximilian University of Munich, Germany & Natural History Museum, University of Oslo
- Researcher, Dr. Quentin Mauvisseau, Natural History Museum, University of Oslo
Summary
Sperm cells are the most diverse cells in the animal kingdom and generally consist of three main parts: the acrosome, midpiece and tail. Among birds, the passerine order (Passeriformes) stands out as having the most elaborate and varied sperm morphology, with marked differences even between closely related species. While the morphological variation and properties of sperm cells have been studied extensively, the underlying molecular causes of this diversity are still poorly understood.
In this thesis, paper I focused on testing and comparing the reliability and sensitivity of three molecular quantification tools, using siskin sperm- and blood samples: quantitative, digital and droplet digital PCR (qPCR, dPCR and ddPCR, respectively). Paper II then employed ddPCR to examine the relationship between mtDNA copy number and sperm midpiece length across 19 songbird species and found no support for a previously expected positive association. Paper III explored how the number of acrosin genes, that are involved in the acrosome reaction, have shifted between non-passerine and passerine birds, using available annotated genomes and testis transcriptomic data.
These studies combined several different methodological approaches and comparative frameworks. Together, they provide valuable technical insights and showcase previously undescribed interspecific molecular differences, thus contributing new findings to the complex field of sperm biology.
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