One of the fish found in Antarctica has a tumor on its face. (Credit: University of Oregon)

Parasitic diseases that spread to the Southern Ocean left grotesque tumors on the fish’s skin.

Scientists say they have never seen such an explosion in the region and believe climate change may be one reason.

Warm conditions can create a more fertile environment for cancer-causing parasites.

This study, published in the journal iScience, describes the tumors as follows:

They were discovered by two scientists, John Postlesswaite and Thomas Desviny, in a large number of fish called nototenoids.

Biologists from the University of Oregon visited the West Antarctic Peninsula to study fish for about 10 years.

This particular fish had adapted to the harsh environment of Antarctica, but in 2018 they noticed a tumor.

Figure 1. Capture site and affected Antarctic nototenoid specimens (A) Animal collection site. The blue line shows the polar front. (B) Three specimens of crowned Nototen Trematomus scotti from Andward Bay, and (C) Painted Nototene pslarsen from Dalman Bay. T. scotti tumors can affect the skin anywhere on the body. N. Larsen's tumor developed under the head and between the pelvic fins. See also Figure S1.

Scientists have studied specimens caught in Antarctica, Andcord Bay, and Dalman Bay. (Credit: University of Oregon)

Working with virologists and pathologists, they determined that the tumor was the result of a parasitic disease. Worryingly, they say this is an unprecedented outbreak of an unprecedented scale near Antarctica.

They say that melting water and ice can contribute to the spread of this particularly fragile ecosystem.

“The difficult living conditions make the animals more susceptible to disease,” said Desvignyes, lead scientist and lead author of the research expedition.

“As soon as I put the first trawl back on deck, I realized that one species was really abundant and a lot of them had big chunks,” says Desvinies.

“When I saw this, I realized that we had to do something immediately.”

Graphic summary Climate change may promote disease outbreaks, but its nature and potential impacts in remote areas have received little attention. In the biodiversity hotspots of the West Antarctic Peninsula, one of the most rapidly changing climates on the planet, we have seen two specimens of notothenoid fish affected by large skin tumors in the Southern Ocean more frequently than ever. Molecular and histological analyzes show that the alveolar X-cell parasite, a representative of the genus we call notox ceria, is the etiology of these tumors. Parasite-specific molecular studies have shown that Zenom persists in the skin but outgrows host cells in the dermis. Furthermore, we observed that the tumor induces angiogenesis in the underlying tissue and has a deleterious effect on the growth and condition of the host. Although there are many knowledge gaps about X-cell disease, such as its mode of transmission and life cycle, these findings reveal a potentially active biological threat to vulnerable Antarctic ecosystems.

Researchers have discovered that the parasite causing the tumor belongs to a different genus than other parasites from previous cases of the disease. (Credit: University of Oregon)

The team collected the infected fish and brought them to the lab for investigation.

Here, they found that the cancer-causing parasite belongs to a different genus than other parasites from previous cases of the disease.

“It can be difficult to pinpoint the specific cause of an outbreak, but the Antarctic ecosystem is particularly vulnerable to the effects of climate change and is undergoing particularly rapid change,” the researchers said.

“For example, when ice melts, nearby water becomes less salty, and the bottom water inhabited by these nototenoids is particularly fast, warm and clean.

Deswines added that fish may be under pressure as waters warm and ecosystems change.

“Climate change may also affect the life cycle of parasites, making parasite spread and infection more efficient,” he said.

There may be weather-related explanations for this spread, but the team said they needed to collect more data before they could say for sure.

antarctic seabed

The waters around Antarctica are warming due to climate change (credit: Getty)

“Perhaps parasites have a long life cycle and often manifest themselves in disease outbreaks. We were there when that happened,” says Desvinies.

“The difficult logistics of visiting the Covid-19 and the Antarctic continent have prevented them from returning to the area ever since.

“We go back there to study this particular outbreak, its evolution after 2018, and we make project proposals to investigate the surrounding area and identify pathogens in other places and in other species. We do it,” Desvinies said.