Many organisms living on the seafloor near the Antarctic continent, especially in shallow water, have to fear that a layer of ice will form on their surface, which is fatal. Only a few species, including sea urchins, starfish and anemones, have developed strategies to prevent icing. Recently, scientists from the Max Planck Institute for Polymer Research (MPI-P) in Mainz, Germany, and the University of Oregon discovered that the Antarctic scallop(Adamussium colbecki) is also resistant to icing and published their findings in the journal Communications Biology.
The ocean temperature around Antarctica is below the actual freezing point of water, down to minus 1.9 degrees Celsius, because of salinity. Especially in shallow water under the ice shelf or in front of ice edges, somewhat colder, so-called supercooled liquid water often occurs. When this supercooled water gets into contact with surfaces (animals, stones, scientific equipment) or tiny particles, ice crystals form. In McMurdo Sound, a layer of these ice crystals up to three meters thick is regularly observed on the seafloor in shallow water, known as anchor ice. In the study, the researchers defined this process as “cryofouling”, analogous to the term biofouling, in which surfaces underwater (ship hulls, etc.) are colonized by organisms.
To escape certain death by icing, creatures in this habitat must use tricks. As the international research team has now discovered, the Antarctic scallop developed a very regular surface structure with microscopic grooves and ridges in the course of evolution. In contrast, their relatives from temperate latitudes have irregular or smooth shell surfaces.
Study leader Konrad Meister, professor of chemistry at the University of Alaska Southeast and research group leader at the Max Planck Institute for Polymer Research in Mainz, Germany, had his attention drawn to the Antarctic scallop by divers during an expedition. The divers reported that they have never observed ice on the surface of this species of mussel.
In the microscope it can be observed that these ridges run radially on the mussel shell and are the places where the water preferentially freezes. The grooves between them remain ice-free. If a continuous layer of ice forms on the shell, it lies only on the elevations and can be washed off again by the smallest underwater currents due to the low adhesion.
For comparison, the research team also conducted icing experiments with a scallop species from warmer regions and found that removing the ice layer was significantly easier for the Antarctic scallop than for the other species.
“It is exciting how evolution has obviously given this scallop an advantage,” says Konrad Meister. “New technological applications based on the principle of bionics are conceivable from the knowledge of the ice-free shell. For example, non-icing surfaces could be highly interesting for polar shipping.”
Julia Hager, PolarJournal
Link to the study: William S. Y. Wong, Lukas Hauer, Paul A. Cziko, Konrad Meister. Cryofouling avoidance in the Antarctic scallop Adamussium colbecki. Communications Biology, 2022; 5 (1) DOI: 10.1038/s42003-022-03023-6.