Adaptations
Through our "Ask the Team" forum, a lot of people have asked, "How do animals, like the worms, survive in the water of McMurdo Sound?"
To understand that, you need to understand the word "Adaptations". Adaptations are changes in behavior, body structures, or at the cellular level that allow an organism to survive in the environment. Every organism (from the tiniest bacteria to the largest blue whale) have adaptations that allow them to survive in their particular habitat.
I spent a bit of time talking with Dr. Marsh about the word "adaptations". He suggested that to look at adaptations here in Antarctica, we should talk about Antarctic fish as our first example.
Behavioral Adaptations
Behavioral adaptations are actions that organisms perform in response to their environment. I bet you can think of one example of a behavioral adaptation that your body does when it gets cold. What does your body do in response to the cold?
You shiver!
That's right! Shivering is a behavioral adaptation. Your body is responding to the transfer of heat energy away from your body. Shivering activates your muscles and produces heat.
Lots of organisms display behavioral adaptations. Sea otters use rocks to open their food by banging their food into the rocks. Weddell seals will keep holes open in the ice by scraping their teeth against the ice. Certain animals are found only in certain locations (like on the bottom) because their behaviors make them very good at living there.
Emerald Notothen (Trematomus bernacchii)
This fish is Trematomus bernacchii, the emerald notothen. (Photo courtesy of Adam Marsh)
This is one of the most common fish we've been seeing on our dives. Dr. Marsh explained to to me that this fish is not very good at moving around in open water. It can't control its height off the bottom very well, because it doesn't have a swim bladder (organ that uses air to keep the fish off the bottom). So, where does it live? On the bottom. It has adapted to life on the bottom and therefore doesn't have the need for structures to help it swim in the middle of the water column. we see this fish exhibiting a lot of behaviors that make sense for a bottom-dwelling fish. It hides in rocks and sponges, usually laying still and trying to blend in with the bottom.
Here is Trematomus bernacchii on the bottom, where it is well adapted to live. (Photo courtesy of Adam Marsh)
See how Trematomus bernacchii blends in. It is well camoflauged. (Photo courtesy of Adam Marsh)
Here Trematomus bernacchii is using a sponge as a hiding place. (Photo courtesy of Adam Marsh)
Structural Adaptations
Lots of organisms have unique parts of their body that they utilize in special ways. A giraffe has a specialized part of its body that is a great example of a structural adaptation. The giraffe utilizes its long neck to reach the leaves in taller trees.
Your thumb is another good example of a specialized body structure. It's unique because it moves in the opposite direction to your other fingers. With this special adaptation, you can grasp and pick things up.
Antarctic fish are another great example to look for structural adaptations.
Most Antarctic fish have structural adaptations that you are very familiar with. Here's a list of just a few:
- Caudal (tail) fin - propulsion, moving through the water
- Dorsal (back) fin - keeping upright and often spiky for protection
- Pectoral (side) fins - turning and stopping
- Gills - breathing
Some Antarctic fish have some more specialized structural adaptations.
Antarctic Cod (Dissostichus mawsoni)
Unlike the emerald notothen, the Antarctic cod is well suited to living in the middle of the water column. To swim in the middle of the water, the Antarctic cod has several adaptations that make it neutrally buoyant (it neither sinks to the bottom nor float up to the ice above). Here's a list of some of the adaptations within its body that makes it possible for it to be successful in the middle of the water:
- Cartilage skeleton (lighter), instead of solid bone (heavier)
- Hollow backbones (vertebrae)
- Changes to digestive system
The Antarctic Cod has several strutcural adaptations, allowing it to live in the mid-water. (Photo courtesy of Wikipedia)
Physiological Adaptations
The term "physiological" is a fancy way of saying adaptations that are happening within an organism, at a level we can't see with just our eyes. These adaptations often involve cells, proteins, or genes within an organism. For example, when you eat a lot of sugary food, your body produces a chemical called insulin that signals a lot of different parts of your body to utilize and store all that food energy. Just like insulin and your body's response to food, many Antarctic organisms have physiological responses to their environment. Several Antarctic fish have developed a protein that help them adapt and survive in the very cold ocean.
Bald notothen (Pagothenia borchgrevinki)
This amazing little fish lives in a most dangerous spot: within the sea ice. You couldn't pick a colder place with more of a chance of freezing. So, how does this organism survive? How can it possibly live where the ocean water around it is freezing without the fish freezing? The answer lies in a physiological adaptation. This fish is protected from freezing by anti-freeze compounds that it produces in its cells. These compounds allow the fish to survive where the water is freezing without their bodies freezing. It's an amazingly useful physiological adaptation. As one of the few fish that can survive living around and in the sea ice, they have access to unique food sources and protection from predators.
Can you find all the Pagothenia borchgrevinki hiding in the anchor ice? They are well adapted to living in a most difficult location! (Photo courtesy of Stacy Kim)