Antarctic fishes that manufacture their own “antifreeze” proteins to survive in the icy Southern Ocean also suffer an unfortunate side effect, researchers report: The protein-bound ice crystals that accumulate inside their bodies resist melting even when temperatures warm. The finding is reported in the Proceedings of the National Academy of Sciences.
“We discovered what appears to be an undesirable consequence of the evolution of antifreeze proteins in Antarctic notothenioid fishes,” said University of Oregon doctoral student Paul Cziko, who led the research with University of Illinois animal biology professors Chi-Hing “Christina” Cheng and Arthur DeVries. “What we found is that the antifreeze proteins also stop internal ice crystals from melting. That is, they are anti-melt proteins as well.”
Five families of notothenioid fishes inhabit the Southern Ocean, the frigid sea that encircles Antarctica. Their ability to live in the icy seawater is so extraordinary that they make up more than 90 percent of the fish biomass of the region.
DeVries discovered antifreeze proteins in Antarctic notothenioid fishes in the late 1960s, and was the first to describe how the proteins bind to ice crystals in the blood to prevent the fishes from freezing.
In the new study, the team investigated whether the antifreeze protein-bound ice crystals inside these fishes would melt as expected when temperatures warmed. When researchers warmed the fishes to temperatures above the expected melting point, some internal ice crystals failed to melt. Ice that doesn’t melt at its normal melting point is referred to as “superheated.”
The researchers also found ice crystals in wild notothenioid fishes swimming in relatively warmer Antarctic summer waters, at temperatures where they would be expected to be free of ice. By testing the antifreeze proteins in the lab, the team found that these proteins also were responsible for preventing the internal ice crystals from melting.
“Our discovery may be the first example of ice superheating in nature,” Cheng said.
A diver himself, Cziko worked with other divers to place and maintain a temperature-logging device in McMurdo Sound, Antarctica, one of the coldest marine environments on the planet. The device recorded ocean temperatures there for 11 years, a substantial portion of notothenioids’ lifespan. Not once in that time did temperatures increase enough to overcome the antifreeze proteins’ anti-melting effect to completely rid the fishes of their internal ice, the researchers report.
The researchers suspect that the accumulation of ice inside the fishes could have adverse physiological consequences, but none have yet been discovered.
If the fishes are destined to carry ice crystals around all their lives, Cheng said, it is conceivable that ice particles could obstruct small capillaries or trigger undesired inflammatory responses. Cziko likens the potential threat to dangers posed by asbestos in the lungs or blood clots in the brain.
“Since much of the ice accumulates in the fishes’ spleens, we think there may be a mechanism to clear the ice from the circulation,” he said.
“This is just one more piece in the puzzle of how notothenioids came to dominate the ocean around Antarctica,” he said. “It also tells us something about evolution. That is, adaptation is a story of trade-offs and compromise. Every good evolutionary innovation probably comes with some bad, unintended effects.”
The long-term temperature record of McMurdo Sound produced in the study also “will prove to be of great importance and utility to the polar research community that is addressing organismal responses to climate change in this coldest of all marine environments,” Cheng said.
Clive W. Evans, a professor of molecular genetics and development at the University of Auckland in New Zealand, also is a co-author of the new paper.
The National Science Foundation supported this research.
To reach Christina Cheng, call 217-333-2832; email firstname.lastname@example.org
To reach Paul Cziko, call 217-819-7976; email email@example.com
The paper, “Antifreeze protein-induced superheating of ice inside Antarctic notothenioid fishes inhibits melting during summer warming,” is available online or from the U. of I. News Bureau.
Links to additional materials:
Paul Cziko’s website with photos of fishes and Antarctic research: www.paulcziko.net
Diana Yates | University of Illinois
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering