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Unusual observation of tumors in Antarctic fish

Antarctica is now the place on Earth displaying the most rapid climate change.
Credit: Thomas Desvignes
L’Antarctique est dorénavant l’endroit sur la Terre qui affiche les changements de climat les plus rapides.
  • L’Antarctique est dorénavant l’endroit sur la Terre qui affiche les changements de climat les plus rapides.
  • Trematomus scotti présentant d’étranges et larges tumeurs sur la peau.
  • Nathalie Rose Le François lors de ses recherches en Antarctique.
  • Nathalie Rose Le François lors de ses recherches en Antarctique.
Unusual observation of tumors in Antarctic fish

The Southern Ocean surrounding the continent of Antarctica has been very stable and extremely cold for several million years. A unique highly specialized wildlife adapted to it and took up residence there in the course of evolution. However, the Antarctic is now the place on Earth displaying the most rapid climate change. Rising temperatures mean that glaciers are melting at a faster pace and in the process contributes to an increase in deep-water temperatures and a decrease in salinity. This unique ecosystem is growing increasingly unstable, and the aquatic wildlife of the Antarctic is particularly vulnerable to these severe and chronic environmental stresses. And as though all that were not enough, the scientific community is now suggesting that climate change could also be nurturing the emergence and outbreaks of diseases.

In a hotspot of biodiversity on the West Antarctic Peninsula, a scientific team at Palmer Station that I’ve been part of since 2013 has been conducting research onboard the icebreaker RV Laurence M. Gould. During experimental nighttime fishing activities, in Andvord Bay we caught an abnormally high number of a species of notothenioid fish, the Trematomus scotti, which presented strange large tumors on their skin. We had never come across this phenomenon during fishing activities in this sector on any of our earlier missions.

The origin of the tumors

The first conjecture of my colleague and the person in charge of the study, Dr. Thomas Desvignes (of the University of Oregon), was that the disease was viral in origin. However, further molecular and tissue analysis on retained samples would confirm that the disease was parasite-induced. The chief culprit is an X-cell parasitic alveolate of the genus Notoxcellia, never observed before. Individuals with these tumors were generally more emaciated (lean) and smaller in size than those in good health. There’s still a lot we don’t know about this parasite and this disease, but at this stage we can’t rule out the possibility of the outbreak spreading to the other T. scotti populations, or expanding geographically and affecting other species of Antarctic fish. Moreover, if we consider the polar environments (the Arctic and the Antarctic) to be the most vulnerable, being at the front line of climate change, it can very easily be imagined that the phenomenon may eventually occur elsewhere on the globe. This discovery was reported in a recent article published in iScience.1

A young artist named Chloe DaMommio has created a comic narrating the progress of this important discovery: “A mysterious disease in Antarctic fish“.

1 Desvignes, T., H. Lauridsen, A. Valdivieso, R. Fontenele, S. Kraberger, K.N. Murray, N.R. Le François, W.H. Detrich, M.L. Kent, A. Varsani and J.H. Postlethwait, 2022. A parasite outbreak in notothenioid fish in an Antarctic fjord. IScience doi.

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