Following on from last week, Kentaro Amemiya, also known as Ameken, from Tokyo Sea Life Park brings you the second installment of his sailing report (click here for last week's article).

Finally, the unmanned submersible Hyper Dolphin will arrive at the deep-sea hydrothermal vents and observe the hydrothermal vent biomes.

The hydrothermal vent we dived into was actively spewing hot water. The substances spewed out along with the hot water had turned the seawater completely white, making it look like we were submerged in a thick bowl of tonkotsu soup. As we proceeded more cautiously, we finally reached a place where the water was clear. There, we found creatures swarming around the hydrothermal vent.

The first thing that caught my eye was the Yunohana crab. Because it lives in hydrothermal vents, it was given a charming Japanese name, derived from the "hot spring deposits" that bloom in hot springs. This crab has no pigment in its body, so its entire body is pure white. Its diet consists of bacteria and shrimp found around the hydrothermal vents. Incidentally, because it has no pigment in its body, it doesn't turn red when boiled, unlike ordinary crabs.

Those Yunohana crabs are climbing up something that looks like a tube. The tube is actually a type of polychaete worm called a Satsuma haorimushi. Satsuma haorimushi create a tube-like structure called a dwelling tube and live inside it. Also, haorimushi harbor bacteria in their bodies as symbiotic partners, and these bacteria use hydrogen sulfide and other substances to chemically synthesize nutrients that the worms obtain to survive. They are a prime example of creatures that have adapted to living around hydrothermal vents.

In addition, there are enormous numbers of shrimp, bivalves, and soles swarming around the hydrothermal vents, but the variety of creatures is not that great. Unlike the shallow seas that are close to us, there aren't many different kinds of fish, shellfish, or crabs.
This is because the area around these hydrothermal vents contains hydrogen sulfide, which is toxic to animals. Only creatures with very special bodily functions that are unaffected by this hydrogen sulfide, or even utilize it, like some tube worms, can live here. The hydrothermal vent community was a collection of unique creatures.

New species of organisms are being discovered one after another in hydrothermal vent communities. However, there are still many mysteries that remain unsolved, such as how organisms migrate to hydrothermal vents hundreds of kilometers away. I look forward to future research that will unravel even more mysteries and wonders of the deep sea.

Well, by the time you read this article, our long yet short voyage will be coming to an end. Until we meet again in the AmeKen series. Thank you for reading.

Photo: A white-skinned crab, the Japanese flower crab (photo by the author)
(Photography assistance provided by: Japan Agency for Marine-Earth Science and Technology [JAMSTEC])

[Tokyo Sea Life Park]

(August 6, 2010)