Scientists have discovered a microscopic organelle unlike any other on Earth, hiding within a mysterious deep-sea creature.

They've called it a 'dragonball' because it exists within the divine dragon glistenworm (Chaetoderma shenloong) – a rare and elusive mollusc found buried deep in the mud at two methane seeps in the South China Sea and, as of this study, one off Japan.

When this species was first discovered in 2024, it was ranked among the top 10 most remarkable finds of the year, according to the World Register of Marine Species (WoRMS).

Today, the divine glistenworm continues to dazzle us.

Specimens dug up from a methane seep in the South China Sea have now revealed a digestive gland riddled with 'dragonballs'.

The results are published in Nature Communications.

Scientists Discover a 'Dragonball' Inside a Rare And Elusive Deep-Sea Creature
Four views of Chaetoderma shenloong, a rare, worm-like deep-sea mollusc found buried in sediment around methane seeps in the South China Sea. (Chong Chen/The Chong Chen Archives/Conchology.be)

The name, dragonball, is a tribute to the famous manga series by Akira Toriyama. It is used to describe a novel structure that scientists found within the membranes of some cells in the glistenworm's digestive system.

When researchers analyzed these microscopic compartments, they were surprised to find a highly complex interior.

Each dragonball is bound by more than 20 membrane layers and houses hundreds of bacteria capable of using chemical energy, rather than sunlight, to produce organic matter.

In the deep, dark sea, the function of the dragonball could be very important to survival.

Researchers in Japan and China argue that dragonballs are the first specialized organelles dedicated to chemosynthesis.

They compare them to little 'farms' of bacteria.

Dragonballs probably help culture special microorganisms that can oxidize sulfur, the researchers suggest, turning this chemical into organic energy.

Scientists Discover a 'Dragonball' Inside a Rare And Elusive Deep-Sea Creature
Electron microscope images of the newly discovered dragonball organelles (dracosphera) inside cells of the deep-sea mollusc Chaetoderma shenloong (a), revealing the symbiotic bacteria packed inside (b) and the organelle's multilayered membrane (c). (Li et al., Nature Communications, 2026)

"A major scientific finding following the discovery of the first deep-sea hydrothermal vent on the Galápagos Rift in 1977 was that many animals inhabiting reducing habitats, such as hot vents and cold seeps, derive their energy and nutrients by 'feeding' on symbiotic bacteria that perform chemosynthesis using inorganic chemicals," the authors explain.

It was already known that some deep-sea animals housed chemosynthetic bacteria in specialized cells called bacteriocytes.

But dragonballs seem to be novel compartments found within those cells. They aren't seen in other molluscs or tube worms.

Scientists Discover a 'Dragonball' Inside a Rare And Elusive Deep-Sea Creature
The deep-sea mollusc Chaetoderma shenloong in its natural habitat (a), its elongated body (b), exposed digestive gland (c), and a 3D reconstruction of its internal anatomy (d), revealing the extensive digestive gland that houses its chemosynthetic bacterial symbionts. (Li et al., Nature Communications, 2026)

Using DNA sequencing, researchers found that dragonballs contain only one type of symbiotic, sulfur-oxidizing bacterial species.

They don't yet understand why the bacteria are packed into dragonballs, but they have a few ideas.

Glistenworms spend most of their lives buried in seafloor sediment, where oxygen is particularly scarce.

Researchers suspect that at some point, the glistenworm breaks down some of the dragonball membranes in its bacteriocytes, thereby releasing the useful bacteria into the rest of the cell to be digested.

In this way, the glistenworm could harvest food from its cellular 'farms'.

This probably can't be done within the dragonballs, as researchers found no lysosomes, the cell's digestive sacs, inside them.

Scientists Discover a 'Dragonball' Inside a Rare And Elusive Deep-Sea Creature
A 3D reconstruction of a dragonball organelle (dracosphera) inside the deep-sea mollusc Chaetoderma shenloong, showing the densely packed symbiotic bacteria (orange) enclosed by the organelle's membranes (blue). (Li et al., Nature Communications, 2026)

There's another explanation as well.

In the deep sea, where oxygen is scarce, keeping the bacteria held within a dragonball could stop them from using up a limited resource, leaving more oxygen for the glistenworm itself.

Scientists Discover a 'Dragonball' Inside a Rare And Elusive Deep-Sea Creature
An illustration showing how the deep-sea mollusc Chaetoderma shenloong may use its Dragon Ball organelles (dracosphera) to protect symbiotic bacteria from oxygen exposure and potentially digest them for nutrients. (Li et al., Nature Communications, 2026)

"Nonetheless," the study authors admit, "due to the lack of living specimens available for experimentation, this hypothesis is primarily derived on correlative evidence and requires physiological validation."

One of the molluscs used for this recent analysis was serendipitously collected from a seep site near a mud volcano off the coast of Japan, extending the species' known range. Who knows when we will find one again.

"Our discovery of an adaptation from one of the most poorly understood animal groups highlights how little we know about the potential of marine invertebrates, especially infaunal deep-sea taxa," the authors conclude.

The divine dragon glistenworm could light the way.

The research has been published in Nature Communications.

This article was fact-checked by Rachel Garner and edited by Peter Dockrill. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.