Scientists Discover 'Life in a Glass Castle' and Dozens of New Species During Japan Deep-Sea Expedition

The June 2025 mission, conducted aboard the research vessel Yokosuka and the manned submersible Shinkai 6500, collected over 528 specimens. In October 2025, global taxonomists convened at JAMSTEC Headquarters for a Species Discovery Workshop to verify these findings and coordinate scientific publication.

Among these discoveries are two breakthrough studies: a comprehensive survey in the journal Ecosphere, led by JAMSTEC researcher Dr Chong Chen, revealing a five-fold increase in known biodiversity at the Nankai Trough cold seeps, and research in The Zoological Journal of the Linnean Society led by Dr. Naoto Jimi, which demonstrates the remarkable evolutionary history of symbiotic sponge-dwelling worms, which have evolved to live 'in a glass castle'.

"The discoveries made in the Nankai Trough and the Shichiyo Seamount Chain remind us how little of our ocean has truly been explored. By supporting missions like this, The Nippon Foundation is helping to open a new frontier of knowledge for Japan and for humanity." Mitsuyuki Unno, Executive Director, The Nippon Foundation

"Each new species discovery made by the Ocean Census is a step toward understanding, valuing, and ultimately safeguarding our shared ocean. This expedition shows what is possible when world-class scientific institutions collaborate to explore the unknown." -  Dr Michelle Taylor, Head of Science, The Nippon Foundation–Nekton Ocean Census

Life in a Glass Castle At the Shichiyo Seamount Chain—a series of deep sea volcanic peaks 500–700 km southeast of Tokyo—researchers discovered an intricate biological relationship within glass sponges. These sponges construct skeletons from silica, creating a rigid, translucent habitat.

Two new species of polychaete worms—Dalhousiella yabukii and Leocratides watanabeae—were found living symbiotically within these structures. The full study is available here.

Expanding Japan's Marine Frontier The Shichiyo seamount dives, previously largely unexplored, also revealed:

• Five new species of squat lobsters, including the genus Munidopsis.
• Newly observed marine life, including octocorals, nemerteans, amphipods, and kinorhynchs.
• Range expansions for several species previously thought rare or absent in Japanese waters.

Together, these discoveries underscore the importance of international collaboration in protecting and understanding the world's hidden marine frontiers.

Media assets via Ocean Census Media Centre 

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