The deep-sea is dark, cold, and ultra-high pressure. Therefore, the deep-sea is a very difficult environment for all creature to survive. Ultra-high water pressure affects structures and skeletons such as fish bladders. When the water depth is deeper than about 5000m, the carbonic acid compound begins to dissolve due to the high water pressure. Calcium carbonate also begins to dissolve without exception. Calcium carbonate crystals form fish bones, shells, shrimp and crab shells. Therefore, it is difficult for organisms to survive in the deep sea. In addition, there is less food for all creature in the deep-sea. In addition, the deep sea is low on food for all creatures. The deepest bottom of the world is the most difficult environment for creatures to survive. However, Hirondellea gigas (H. gigas) can survive in the deepest bottom. How can they survive?
Hirondellea gigas can digest plant debris with their unique cellulose.
H. gigas is a kind of amphipods. Almost all amphipods are scavengers in the food chain. Scavengers eat and decompose the carcasses of other animals. However, the biodensity is very low in the deepest sea. H. gigas is unlikely to encounter corpses and cannot be expected as food. If H. gigas cannot eat, they will starve to death. However, many H. gigas live in the deep sea and are active. They would eat other foods than corpses. Usually, researchers check the contents of the stomach to find out the food of the animal. H. gigas is always caught with baited traps, and their stomach contained the bait. Then, the digestive enzymes of H. gigas were studied to find what they can digest and nourish. Very interestingly, H.gigas had cellulase. This cellulose is unique cellulose to produce glucose from plant debris. Glucose is an essential nutrient for all animals. Unlike forests, most sea creatures do not eat tree branches, deciduous leaves, or fallen trees that have fallen into the sea. Then, these plant debris fall into the deep sea. H. gigas has adapted to the deep sea by nourishing it from plant debris. If you would like to know more details, please read the following paper.
Next, I will upload Blog about the secret of H. gigas’s shell. Why don’t their shells dissolve?