Antarctic fish survive in freezing waters thanks to antifreeze proteins (AFPs) in their blood.
These remarkable proteins are the key to their survival in the sub-zero temperatures of the Antarctic Ocean. Here's a breakdown of how they work:
The Role of Antifreeze Proteins (AFPs)
- Prevent Ice Crystal Formation: AFPs bind to tiny ice crystals that begin to form in the fish's body fluids. This binding prevents the crystals from growing larger and causing cellular damage, which would lead to freezing.
- Lower Freezing Point: Although they don't drastically lower the freezing point of water, AFPs significantly hinder ice crystal growth. This subtle difference is enough to keep the fish's blood and tissues from freezing solid.
- Unique Macromolecules: These proteins are unique macromolecules specifically adapted to function in extremely cold conditions. They are highly effective at preventing ice formation even in very small concentrations.
How Antifreeze Proteins Work: A Closer Look
While the precise mechanism of how AFPs inhibit ice growth is still being studied, the current understanding is that they function by:
- Adsorption: AFPs adsorb (stick) to the surface of ice crystals.
- Curvature Effect: This adsorption prevents the crystals from forming the necessary curvature for further growth, effectively halting their expansion.
- Inhibition: By inhibiting crystal growth, AFPs prevent the fish's bodily fluids from solidifying.
Example
Many species of Antarctic notothenioids, a dominant group of fish in the Southern Ocean, rely on AFPs for survival. These fish have evolved specific types of AFPs tailored to the unique challenges of their icy environment.
In summary, Antarctic fish don't freeze because they have evolved antifreeze proteins in their blood that inhibit ice crystal formation and prevent the fish's body fluids from solidifying.
