Antarctic scallop protected from ice build-up | Polarjournal
The special, regular surface structure of the shell probably saves the life of the Antarctic scallop. Thanks to fine grooves, ice cannot stick to it and is washed away by the current. Image: Max Planck Institute for Polymer Research

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.

(a – c): Antarctic scallops are not affected by cryofouling as long as there are no sponges settling on their shells, where ice crystals may well form, causing them to float to the surface due to lower density, as shown in photos (d – h). Figure: Wong et al. 2022

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.

Ice formation is concentrated on the tiny ridges in the Antarctic scallop (left), whereas the scallop species from warmer regions where ice formed irregularly or over the entire surface. Figure: Wong et al. 2022

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.

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