CrispResist project have sought answers as to why some Pacific salmon species are more resistant to sea lice than Atlantic salmon for four years
The member of the Norwegian Institute of Food, Fisheries and Aquaculture Research (Nofima), Lene Sveen, is the lead author of a recent scientific publication that closely examines the interaction between sea lice and salmon. The study analyses the immune responses of different salmon species to sea lice attacks, with the hope of improving the responses of Atlantic salmon in the future.
Sea lice remain one of the most important challenges in the aquaculture industry, and scientists are working tirelessly to develop knowledge that can lead to new solutions. “When sea lice attach, certain Pacific salmon species mount a rapid and robust response, causing the lice to fall off,” says the Nofima researcher.
In the recent study ‘Local inflammation at the salmon louse (Lepeophtheirus salmonis) attachment site contributes to copepodid rejection in coho salmon (Oncorhynchus kisutch), Sveen and her colleagues focused on coho salmon, long recognized for their natural resistance to sea lice. Instead of looking at the entire immune system, the scientists focused on where the louse first attaches to the skin, a decision that turned out to be a good idea.
Powerful Inflammatory Reaction
The scientists discovered that coho salmon trigger a powerful inflammatory reaction within two days of louse attachment. Immune cells flood the louse attachment area, making it difficult for the parasite to establish itself. In contrast, Atlantic salmon show a much weaker response.
“This is precisely where the battle begins. If the salmon can respond quickly enough, it can prevent the louse from gaining a foothold,” says project leader Nick Robinson at Nofima.
Not only coho salmon, but also other Pacific species such as chum and pink salmon, demonstrate impressive defenses against sea lice. The study reveals that these species have a high density of mucous cells in their skin. During the experiment, the salmon had to be anaesthetized for the sea lice to attach successfully.
“This suggests that their skin surface is inherently unsuitable for the parasite in some of these other species, and that several mechanisms are at play, making it difficult for lice to successfully establish,” Sveen explains.
Comparing Species for Four Years
The research was conducted as part of the CrispResist project, which brings together an international team of experts from both science and industry. For four years, they have sought answers as to why some Pacific salmon species are more resistant to sea lice than Atlantic salmon. Their efforts have been cumulative, and much of the pieces in the puzzle are now in place.
“We have never been closer to the answer about how species like coho defeat sea lice, and these new findings have sparked several new ideas for further research that will bring us closer to solutions for Atlantic salmon,” says Sveen.
CrispResist, a Unique Study
The aim of CrispResist project is to identify the underlying mechanisms behind species-independent variation in host resistance to sea lice, using this knowledge to enhance resistance in Atlantic salmon. The initiative is funded by the Norwegian Seafood Research Fund (FHF).
What makes this particular study unique within CrispResist is that by zooming in on the initial contact point between louse and host, scientists have uncovered early, highly localized immune reactions that would otherwise be diluted in whole-body analyses.
Technological advances have enabled a combination of various highly sensitive analytical methods to be deployed, providing a new understanding of how the immune system is activated.
The partners in the project are Nofima, University of Edinburgh, University of Prince Edward Island, University of Stirling, Bigelow Laboratory of Ocean Sciences, University of Bergen, University of Gothenburg, Rothamsted Research, Institute of Marine Research, Deakin University, Benchmark Genetics, Mowi and Salmar.
