Life in water colder than ice
On Wednesday night, Sept. 7, visiting scientists Christina Cheng and Art Devries gave a lecture on how polar fishes avoid freezing in their icy environments.
Devries opened with an anecdote about how other organisms survive in the cold. One example is the Weddell Seal, which gives birth to their pups in October when it’s 30 degrees below Celsius. At this temperature, the seal’s amniotic fluid immediately freezes and sheds off the pup’s fur. If the temperature is too warm than the fluid won’t freeze and the pup won’t dry off. For these animals it’s better to be born at 30 degrees below C. than zero degrees C.
The ocean water around in Antarctica varies between 2 degrees below C. and 2 degrees C. which can be colder than the freezing point of water. The reason this is possible is because the dissolved salt in ocean water makes freezing more difficult.
The fish that live in this environment survive while other organisms would freeze solid. How this is possible, is the question of Devries’ research.
“As Alaskans and Fairbanksans, we are very used to ourselves and the animals here that get ready for the winter,” UAF’s Dean of the Graduate School, Michael Castellini said. “These fish are in winter all they time, they never get away from the freezing problem.”
The majority of fish in the antarctic waters are under the classification of Family Nototheniidae. They make up 91.6 percent of individuals and 76.6 percent of the species diversity. Sometimes called “Antarctic Cods”, these fish do not freeze because they have antifreeze in their blood.
However, as the lecture’s title states “Not your Chevy’s Antifreeze: How Polar Fishes Avoid Freezing,” this antifreeze is different. It is a protein that the fish produces to stop freezing by absorbing ice crystals as they form.
These fish are not the only ones that Cheng and Devries studied. They also looked into a variety of other fish, some who used less of the antifreeze protein or none at all. These other fish used different methods of surviving the biting cold, such as the Antarctic Dragon Fish which has skin that prevents the spread of ice.
“This range of solutions to the same problem is very typical of a biological solution,” Castellini said. “Different animals solve the problem in different ways.”
A common question that Cheng and Devries get is whether this protein can aid with cryopreservation of people. While this doesn’t seem feasible, the protein can be useful for the preservation of things like ice cream, according to Cheng.
“The story hasn’t finished yet,” Cheng said during the conclusion of the presentation. She listed many of the things about these polar fishes that are still not understood. While the fish itself might have mechanisms to avoid freezing, all of its systems also need to be able to operate at such extreme temperatures. That’s something that is still not fully understood.
Cheng and Devries presented for UAF’s annual Laurence Irving and Per Scholander Memorial Lecture. Every year since 1981 the IAB and the Institute of Marine Science sponsor the Irving-Scholander Lecture to honor Irving and Scholander for their contributions to biological knowledge.
Cheng and Devries declined to accept their honorarium instead the money was given to two graduate students whose research demonstrated the spirit of Irving and Scholander’s research.
The first award from the Institute of Arctic Biology went to Don Larson who studies the freezing and thawing cycles of Alaskans Wood Frogs. The second award from the Institute of Marine Biology went to Casey Clark who studies the changes in walrus populations.