Japanese scientists find “crystal castle” in an unexplored region at the bottom of the ocean

With the help of a manned submersible, a team of Japanese scientists descended to the bottom of the ocean, almost 1,000 meters deep, and identified a surprising marine organism — a delicate structure that serves as a refuge for other marine species.

A scientific expedition led by Japan descended to a depth of almost 1,000 meters in a virtually unknown region of the ocean and identified a surprising marine organismwhich researchers compare to a crystal castle.

The discovery was initially presented in a paper published in November in Ecosphereand detailed in a published on Monday in Zoological Journal of the Linnean Society.

The research is part of the Nippon Foundation-Nekton Ocean Census expedition, carried out in June 2025 in collaboration with the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), during which scientists explored two of the least studied areas of the Japanese seafloor: the Fossa de Nankai and the seamount chain Shichiyo.

Among the discoveries, one stands out glass sponge (class Hexactinellida), an organism whose structure is composed of silica, the same material that makes up glass. This characteristic gives rise to a skeleton in the form of a transparent network, which is reminiscent of a crystalline structure at the bottom of the sea.

The organism was photographed at approximately 791 meters depth thanks to the manned submersible. The image captured during the immersion reveals a delicate structure that serves as shelter for other species marine life that live inside it.

The study, led by investigator Naoto Jimidescribes how two species of polychaete worms, Dalhousiella yabukii e Leocratides watanabeaeseem to have evolved to live inside these sponges.

The scientists compare this relationship to life inside a crystal castle, as the worms use the structure as protection. The research suggests that the sponge itself could represent a species not yet described by science.

This relationship between organisms demonstrates the complexity of ecosystems of the deep ocean and the way different species depend on natural structures to survive.

As explained Mitsuyuki Unnoexecutive director of The Nippon Foundation, on , “the discoveries made in the Nankai Trench and the Shichiyo seamount chain remind us how little we explore truly our ocean.”

The researchers emphasize that just 0.001% of the ocean depth has been directly observed, which suggests that numerous species remain undiscovered.