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Sperm performance traits exhibit low additive genetic component and strong parental effects in external fertilizer
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics. (Simone Immler)
University Pablo de Olavide, Ctra.
Friedrich Schiller University Jena.
University of East Anglia.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Despite their key role in determining reproductive success and with that Darwinian fitness, the heritability and underlying additive genetic variance of reproductive traits is still not fully understood. While some traits show relatively high genetic variance, others show very low genetic variance, which is particularly true for complex non-morphological traits. In line with these general patterns, morphological sperm traits show surprisingly high heritability, whereas heritability reported for sperm quality and performance traits generally is lower. A possible explanation for this is the general notion that more fitness related traits show lower levels of additive genetic variance and heritability. We investigated the additive genetic variance and heritability of sperm swimming velocity, the percentage of motile sperm, sperm concentration in the ejaculate and sperm longevity in the externally fertilizing zebrafish Danio rerio. All sperm traits showed low but significant additive genetic variance and high parental components. While the additive genetic variance was significant it was lower than reported in many other studies. A possible explanation for this is that in externally fertilizing species, sperm traits are the prime determinant of fertilization success and high plasticity is crucial for swift adaptations to changes in the environmental conditions such as competition but also water temperature and currents. Given that this is the first study looking into the heritability of sperm traits in an external fertilizer it will be interesting to understand, whether this is true for other externally fertilizing species and taxa.

Keywords [en]
additive genetic, parental effect, sperm traits, reproduction
National Category
Evolutionary Biology
Research subject
Biology with specialization in Evolutionary Genetics
Identifiers
URN: urn:nbn:se:uu:diva-350191OAI: oai:DiVA.org:uu-350191DiVA, id: diva2:1204341
Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-06-01
In thesis
1. Haploid selection in animals: Exploring the fitness consequences and underlying mechanisms
Open this publication in new window or tab >>Haploid selection in animals: Exploring the fitness consequences and underlying mechanisms
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A consequence of sexual reproduction in eukaryotes is the evolution of a biphasic life cycle with alternating diploid and haploid gametic phases. While our focus in evolutionary biology is on selection during the diploid phase, we know relatively little about selection occurring during the haploid gametic stage. This is particularly true in predominantly diploid animals, where gene expression and hence selection have long been thought to be absent in haploid cells like gametes and particularly sperm. During my PhD, I tested the idea of selection during the haploid gametic phase using zebrafish Danio rario as a study species. I combined a large-scale selection experiment over three generations with fitness assays and next-generation sequencing to assess the importance of haploid selection. We measured offspring fitness in all three generations.  In addition, we compared gene expression in brain and testes of F1 and F3 adult male from each treatment by RNA sequencing. We found that offspring sired by longer-lived sperm showed higher survival rate and higher early- and late-life reproductive fitness compared to offspring sired by shorter-lived sperm. We also found differentially expressed genes between the two treatments with functions in metabolic and developmental pathways. These findings suggest that the observed fitness differences to be caused by small expression changes in many basic genes. We also tested for a genetic underpinning of the selected sperm phenotypes and identified allelic differences across the entire genome. Finally, we investigated the additive genetic component and parental effect of different sperm phenotypes. We found generally low additive genetic variation and high parental effects on sperm performance traits. In conclusion, this thesis provides evidence that the phenotypic variation among intact fertile sperm within an ejaculate affects offspring fitness throughout life and provides a clear link between sperm phenotype and offspring fitness and between sperm phenotype and sperm genotype.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 41
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1681
Keywords
sperm, evolution, haploid selection, reproductive aging, fitness
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-350192 (URN)978-91-513-0358-1 (ISBN)
Public defence
2018-09-14, Lindahlsalen, Norbyvagen 18d, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2018-08-24 Created: 2018-05-07 Last updated: 2018-09-06

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