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Paralog switching facilitates diadromy: ontogenetic, microevolutionary and macroevolutionary evidence
Rebecca S Colby1,2, Stephen D McCormick3,4, Jonathan P Velotta5
1Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA.
Oecologia
|July 16, 2024
Summary
Gene expression in fish gills shows paralog switching of the sodium-potassium pump (Na+, K+-ATPase) is key for adapting to different water salinities during migration. This adaptation evolved independently in different fish lineages.
Area of Science:
- Genomics and Molecular Biology
- Physiological Ecology
- Evolutionary Biology
Background:
- Diadromous fish migration between freshwater and seawater necessitates significant osmoregulatory adjustments.
- The gill ion pump Na+, K+-ATPase (NKA) is crucial for osmoregulation, with paralogs (NKA α1a and NKA α1b) showing reciprocal upregulation in different salinities.
- This paralog-switching response is a known adaptation in some migratory fish species.
Purpose of the Study:
- To investigate ontogenetic and microevolutionary changes in NKA α-subunit paralog expression during alewife migration.
- To explore the macroevolutionary origins of NKA paralogs in relation to diadromous life history.
- To determine the link between NKA paralog switching and habitat salinity.
Main Methods:
- Comparative analysis of NKA α-subunit paralog expression in pre-migrant and migrant alewife (Alosa pseudoharengus) under different salinity conditions.
- Experimental exposure of juvenile diadromous and landlocked alewife to freshwater and seawater to assess salinity-dependent gene expression.
- Phylogenetic analysis of alewife NKA paralogs to understand their evolutionary history in teleosts.
Main Results:
- Juvenile out-migrant alewife showed stronger NKA paralog switching (downregulation of NKA α1a) in seawater compared to pre-migrants.
- Both diadromous and landlocked alewife exhibited salinity-dependent paralog switching, with diadromous fish showing higher NKA α1b and greater NKA α1a downregulation in seawater.
- Molecular phylogenies indicated independent origins of alewife NKA paralogs compared to other teleosts.
Conclusions:
- NKA paralog switching is directly linked to habitat salinity and plays a critical role in the osmoregulatory challenges of diadromous migration.
- Gene duplication events provided the evolutionary basis for independent molecular solutions supporting diadromous life histories across different fish lineages.
- Understanding these gene expression patterns is vital for comprehending migratory physiology and the evolution of migratory behaviors.
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