Salmon's skin transformation during ocean migration puzzles researchers
Atlantic salmon undergo dramatic skin changes as they transition from rivers to seawater, but scientists discovered the mechanism isn't what textbooks predicted. The finding has implications for aquaculture operations managing salmon in both freshwater and marine environments, where skin health directly affects fish survival and production costs.
Originaltitel: Variation in skin barrier function throughout smoltification in Atlantic salmon (Salmo salar)
Atlantlaxens hudbarriär försvagas under smoltificering, särskilt efter exponering för saltvatten — en upptäckt som påverkar framtida uppfödningsstrategier för laxindustrin. Forskare från Göteborgs universitet och Universitetet i Bergen mätte elektrofysiologiska parametrar hos lax i tre livsstadier: yngel (parr), smolt och postsmolt. Resultaten visade att yngelns hud var betydligt mer permeabel än smoltens, med lägre transepithelial resistans och mer negativ kortslutningsström. När postsmolter exponerades för saltvatten ökade den transepithelala potentialen jämfört med smolter. Överraskande fann inte forskarna motsvarande förändringar i uttryck av täta-knutproteiner, vilket tyder på att andra claudinisoformer eller posttranskripsjonella mekanismer driver förändringarna. För laxodlare innebär detta att hudintegritet blir kritisk under smoltificering och saltvattenöverflyttning. Operativ prioritering av hudskydd under denna period kan förbättra överlevnad och tillväxt.
Introduction Smoltification involves distinct morphological, physiological and behavioral changes in Atlantic salmon, yet skin barrier function has not been functionally assessed throughout this transition. Method We measured electrophysiological parameters at three life stages — parr, smolt, and post-smolt — to assess changes in skin permeability and transport capacity. Results Parr skin showed significantly lower transepithelial resistance (higher permeability) and more negative short-circuit current than smolts under identical Ringer`s conditions. Seawater exposure elevated transepithelial potential in post-smolt relative to smolt, while freshwater exposure elevated short-circuit current in smolt relative to parr. No significant differences in mRNA expression of selected tight junction genes were found between life stages. We detected no significant correlation between skin permeability and any of the selected genes. Discussion The results suggests that other claudin isoforms or posttranscriptional mechanisms underlie the observed functional changes. From a husbandry perspective, elevated skin permeability following seawater exposure highlights the importance of prioritizing skin health during and after smoltification, as skin function may be compromised at this time.