How to capture the animal living in the deepest region in the ocean
- Hideki Kobayashi
- Jul 2
- 3 min read
Lives in the deep sea have unique form. Sometimes they become very large size. For example, Giant squid can grow to a total length of 10 meters or more. And then there is a creature that shines with a beautiful radiance. There are many unknown species of deep-sea creatures. Because, they are found in very small numbers across vast areas. As a result, researchers find it difficult to collect the deep-sea creatures they are studying according to schedule., The hydrothermal vents are hotspots for certain creatures, however, it is difficult to collect them. They are attracted to hydrothermal vents. Researchers have to collect them one by one using the submersible’s manipulator.
What is Hirondellea gigas?
Hirondellea gigas is one of creatures living in the deepest region in the ocean. If you are interested in deep-sea creatures, you have likely heard the name at least once. H. gigas resembles a shrimp in appearance. However, it is not a shrimp, but a type of amphipod. Amphipods play the role of decomposers within the ecosystem. They primarily feed on the dead bodies of organisms. In coastal areas or on land teeming with life, they would likely be able to obtain plenty of animal carcasses. In contrast, the deep sea is an environment with extremely few living organisms. Therefore, deep-sea amphipods feed on the carcasses of organisms that fall from land or coastal areas. Carcasses sinking into the deep sea are consumed by deep-sea organisms. As a result, their numbers decrease with increasing depth. The ultra-deep-sea zone inhabited by H. gigas is likely one of the most nutrient-poor environments in the world. In fact, only H. gigas, sea cucumbers, foraminifera, and bacteria have been found at the deepest point of the Mariana Trench—the Challenger Deep. H. gigas was swimming very actively, despite the high water pressure and nutrient-poor environment. How do they obtain nutrients? This was one of the greatest mysteries surrounding deep-sea organisms.
Why can H. gigas survive at the hadal sea?
One of the answers to this mystery lay in the digestive enzymes of H. gigas. It possessed cellulase as a digestive enzyme. The cellulase derived from H. gigas was able to decompose wood chips and fallen leaves to produce glucose. Most deep-sea organisms cannot derive nutrition from plant fragments such as driftwood or fallen leaves. Consequently, the majority of plant debris that washes into the ocean sinks to the seafloor. In fact, it contained cellobiose, a by-product of the cellulase reaction. It can obtain glucose from pieces of wood and fallen leaves that have settled on the deep-sea floor.
Why do researchers want H. gigas?
Many researchers are interested in H. gigas. One of their areas of interest is that unique cellulase. The cellulase from H. gigas can break down sawdust, bamboo, and paper to produce glucose. Glucose is a raw material for ethanol fermentation. Ethanol fermentation is utilized not only in the production of alcoholic beverages but also in the production of bioethanol. Furthermore, this cellulase reacts at around 25–30°C. Therefore, this cellulase is a highly useful enzyme, with applications ranging from the food industry to renewable energy production.
Actually, capturing H. gigas does not require advanced marine exploration equipment.
H. gigas inhabits in the hadal zone. To capture H. gigas for research purposes, it is necessary to lower equipment down to the hadal zone. Many people would likely think that advanced equipment from a marine research institute is needed to do that. We successfully captured H. gigas using a simple mooring system “Edokko No.1” and a fishing vessel. We have compiled the records of our capture voyages into a single book. No scientific knowledge is required at all. Everyone, from children to adults, will enjoy reading this book.
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