Subzero water is a death trap for most animals. Icefish, on the other hand, make their home in it. A unique property of their blood makes this possible.
You might be reading this outside, basking in the warm sunlight, iced drink in one hand. Maybe you’re on the beach, salt wind in your hair, sunglasses leaving faint tan lines on your cheeks. Or maybe you’re enjoying a cup of coffee in the quiet moments of the morning.
Now recall a time when you could find no warmth, when the cold grasped your bones and chattered your teeth. Do you remember that feeling?
Antarctic icefish happily live in the ocean waters surrounding Antarctica. The temperatures there often remain below freezing, making survival difficult for most living creatures. Saltwater freezes at a lower temperature than freshwater due to the salt’s disturbance of water’s crystallization. Though the water outside remains liquid, the frigid cold still causes the water in a fish’s veins to freeze. Such freezing will prove fatal to any creature not prepared for it.
Within the blood of the Antarctic icefish is a special protein that acts as an antifreeze.
But no worries for the icefish. How does it manage to survive—and thrive—in such frigid waters? Just as one sparrow will not fall apart from the Father’s care (Matthew 10:29), He carefully provided for the pale icefish as well.
Within the blood of the Antarctic icefish is a special protein that acts as an antifreeze. When the ocean’s temperatures drop, the water in the icefish’s blood will begin to crystallize. However, the antifreeze protein latches onto the growing ice, forcing the water molecules to disperse and remain fluid. This specific design allows the icefish to enjoy a habitat with little competition for limited resources, so it can thrive in the quiet waters near the South Pole.
But stopping ice from forming in your veins is not enough to ensure good health in bitter cold. Under such conditions our blood (along with the blood of many other warm-blooded creatures) would thicken and cease to flow, overtaxing the heart’s circulation, leading to a slow end. How does the icefish’s circulatory system keep from becoming overwhelmed?
Antarctic icefish are the only known vertebrate on the planet to have no red blood cells or hemoglobin in their blood.
Antarctic icefish are the only known vertebrate on the planet to have no red blood cells or hemoglobin in their blood. Red blood cells are used to transport oxygen from the lungs to the rest of the body. Hemoglobin is the iron-based protein that combines with the oxygen, often within the red blood cells. However, the presence of these cells makes blood much thicker and sluggish in colder weather.
Icefish use a much simpler method of oxygen transportation. Since Antarctic waters are more oxygen-rich than other oceans, the icefish can absorb oxygen directly into their plasma, which then transports the oxygen to the rest of the body. Their clear blood is so much thinner than that of other animals that the fish appears translucent.
Surviving in the cold is no easy task, no matter how easy the icefish makes it seem. Be grateful our blood is red, soak up the warmth of the sun, and count your blessings that you don’t live in such a cold place.