The record of deep sea biology has been rewritten by a Japanese research group. During sampling in the Kuril-Kamchatka Trench, located in the northwestern Pacific Ocean, researchers from Hokkaido University sampled unusual leathery black cocoons attached to rock samples at a depth of 6200 meters.The cocoons were 3-millimeter-wide, leathery black capsules, Biology Letters reports; The cocoons contained embryos of free-living flatworms (phylum Platyhelminthes). The investigators found the embryos to be immersed in nutrient-rich yolk, which provided protection to the developing embryos from the extreme pressure of the deep-sea environment. Hokkaido University indicated that the discovery provides a new world record for this species of flatworm (at the deepest known location to date) and that lifeforms with complex, relatively simple body plans are essentially similar and can continue to exist no matter how much pressure deep-sea lifeforms experience.
A record-breaking discovery at 6,200 meters beneath the Pacific Ocean
As part of their research at the Kuril-Kamchatka Trench in the northwest Pacific, a Japanese research team recovered several exotic, jet-black ‘eggs’ attached to fragments of rock. According to the study published in Biology Letters, the specimens were discovered at a depth of 6200 meters (more than 20,000 feet). The discovery provides a new world record for the deepest known location of a free-living flatworm, as they were found at almost twice the depth of the previous record of 3,232 metres.
What was inside? mystery of the black cocoon
Although the structures were about 3 millimeters in diameter, they were not actually eggs, but rather leathery egg capsules (known as cocoons). When Dr. Keiichi Kakui of Hokkaido University opened the cocoons using a microscope, a milky liquid (later identified as yolk) oozed out of each cocoon. According to research archived by Royal Society Publishing, each egg capsule contains three to seven flatworm embryos, some of which already show signs of developed internal organs.
deep sea survival blueprint
An unexpected discovery from this study was that there are few species of flatworms in the abyssal zone of the ocean, and many members of the flatworm family have similar embryonic morphology. Because their embryonic development did not require them to undergo major changes, these organisms were able to move from shallow coastal waters to the abyssal zone over the course of geological time. This was accomplished through a ‘time capsule’ that developed around their eggs as they grew into adults, thus protecting them from the underwater pressure and harsh chemical environment of the abyss.Accordingly, finding intact embryos at such depth is a first for this study (as it could not be predicted). Therefore, these findings establish a foundation on which additional studies can be conducted to learn how organisms with simple body plans have been able to move from the world’s shallow shores to the deepest regions of our oceans over geological time.