A large number of Antarctic fish have been found with tumors on their bodies.
According to a study published in the journal iSciencethese tumors are caused by a parasitic infection whose effects are aggravated by climate change.
The authors discovered the grotesque-looking fish during an expedition to West Antarctica in 2018. They noticed that in two species of crowned notothen, about 30% of specimens had tumors. They were pale pink, raised, rough, and often covered more than a third of the fish’s body surface. The researchers had visited this same area, which includes Andcord Bay and Dallmann Bay, four years earlier, but found no examples of fish with these tumours.
“As soon as we put the first trawl back on deck, we realized that one species was really abundant and that many of them had large tumors,” Thomas Desvignes, lead author of the study, said in a statement. communicated. “When we saw that, we immediately realized we had to do something.”
Once back in the lab, the team analyzed the tumors and discovered that the fish had X-cell disease, a cancerous infection caused by a new species of Xcellidae, a honeycombed parasite (the same type of protozoan that causes malaria). Wild fisheries in Iceland and Norway have already reported infections by Xcellidaebut how it is transmitted is not yet known.
Notothenoid fish are infamous for their adaptations, which allow them to live in the coldest waters on earth. The fish have evolved a glycoprotein that lowers their blood freezing point to just below the freezing point of seawater (28.4 F), allowing them to survive in the freezing waters of Antarctica.
The researchers postulate that the sudden and dramatic increase in infections by Xcellidae may be linked to rising seawater temperatures due to climate change.
“Although the sea floor temperatures at our capture sites are not dramatically different from those at other nearby locations, the glaciers of the West Antarctic Peninsula are melting at a rapid rate, affecting the Antarctic bottom waters. , which have warmed and cooled for several decades,” the authors said. said in the newspaper.
Warmer waters may improve the dispersal or infectivity of Notoxcellianew Xcellidae species that infect Antarctic fish, or potentially weaken icefish, making them more susceptible to infection.
“When living conditions become difficult, animals become more prone to disease,” Desvignes said.
Rising global temperatures caused by climate change are also warming the ocean. West of the Antarctic Peninsula, upper ocean temperatures have risen more than 34 F since 1955, with the Antarctic Circumpolar Current warming at a faster rate than the rest of the Southern Ocean. This, combined with the resulting melting sea ice, is already impacting the Antarctic ecosystem, leading to long-term declines in Antarctic krill abundance and changes in penguin distribution.
“While we currently lack data and knowledge to predict how X-cells might be affected by global climate change, with alarming predictions of continued changes in Antarctic climates, this dramatic situation in this population may predict biotic changes at large-scale parasite-host interactions triggered by changes in the abiotic environment,” the study authors said.
The authors added that they need to do more research to better understand and quantify parasitic infection, how it spreads between fish, and how climate change will affect it in the long term.
“We are preparing project proposals to go back there and study this specific outbreak, how it has evolved since 2018, and explore adjacent areas to try to see if we can detect the pathogen elsewhere and in other species,” Desvignes said. in a press release.