Meeting Abstract
The invasion of freshwater from marine habitats prompted extensive diversification of aquatic taxa. Mechanisms permitting this habitat switch can be investigated in extant euryhaline fishes, those that can tolerate a wide range of salinities. Taxa that have undergone genome duplication events are of particular interest as resulting paralogs may contribute to such flexible osmoregulation. Two paralogs of Na+, K+-ATPase (NKA), an important ion transporter, occur in the gills of salmonids and are differentially expressed in freshwater (FW) and seawater (SW). These paralogs, NKA α1a and α1b, share a single evolutionary divergence in Salmonids. Our study sought to identify NKA paralogs in an early branching lineage of teleosts, Alewife (Alosa pseudoharengus), test their function, and reveal their phylogenetic relationship to those of salmonids. We found NKA paralogs in Alewives and they were differentially expressed in FW and SW. Notably, in landlocked populations of Alewives differential expression is dampened, possibly due to lack of selective pressure favoring SW tolerance. The divergence between the Alewife paralogs predates that in salmonids. This indicates that multiple molecular solutions have arisen for adapting to freshwater within the same gene.
