Understanding sperm-egg interactions using fish and insect models
Sperm-egg interactions operate at the end of the struggle to reproduce and therefore have a significant influence over reproductive fitness and gene flow. In this thesis I utilise the externally fertilising Atlantic salmon and internally fertilising T. castaneum as complementary model species to und...
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| Format: | Thesis |
| Language: | English |
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2021
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| Online Access: | https://ueaeprints.uea.ac.uk/id/eprint/89971/ https://ueaeprints.uea.ac.uk/id/eprint/89971/1/JB%20Final%20PhD%20thesis.pdf |
| Summary: | Sperm-egg interactions operate at the end of the struggle to reproduce and therefore have a significant influence over reproductive fitness and gene flow. In this thesis I utilise the externally fertilising Atlantic salmon and internally fertilising T. castaneum as complementary model species to understand sperm-egg interactions. Atlantic salmon’s (Salmo salar) external fertilisation system allows control and paired in vitro fertilisation experiments to reveal drivers and mechanisms of sperm-egg interactions. Tribolium castaneum flour beetles also enable tight control and generous replication, plus a generation time that enables experimental evolution. These systems and approaches were used to investigate both applied and fundamental questions about reproduction, fertilisation and gametic interactions in both wild and farm salmon. In Atlantic salmon, aquaculture and conservation hatcheries employ an artificial fertilisation process to reproduce offspring, which can sometimes lead to suboptimal hatch rates. Across a series of fertilisation tests, where potential factors within standard hatchery and farm gamete handling methods were investigated, we found wild Atlantic salmon hatch rate to be maximised when eggs were fertilised ‘dry’ (gametes are mixed together before the addition of river water) on the day of gamete stripping. In farm Atlantic salmon, we found no particular gamete handling factor to affect hatch rates, with females and eggs also able to tolerate external storage for extended periods of time. Overall, in both farm and wild fish, hatch rates were maximised when fertilised ‘dry’ with minimal post-ovulatory storage duration, and we found no evidence that any of these artificial gamete handling factors increased the risk of abnormal ploidy levels among offspring. However, if such storage is needed, eggs should be left within the coelomic cavity for up to 14 days, rather than exposing females to multiple checking and stripping events. Despite genetic and phenotypic divergence between wild and farm ... |
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