Plate Nº 19 · recorded November 14, 2026
Biology & EvolutionReported finding
‘Dragonball’ Organelle Found in Deep-Sea Mollusc May Be First Built for Chemosynthesis
A rare deep-sea mollusc harbors bacteria-packed organelles with 20-plus membrane layers, possibly the first cell structures built for chemosynthesis, researchers report.
By Elena Vasquez3 min read631 words
In brief
- Researchers describe 'dragonball' organelles with more than 20 membrane layers inside the deep-sea mollusc Chaetoderma shenloong.
- Each dragonball houses hundreds of bacteria of a single sulfur-oxidizing species, per DNA sequencing.
- The species was discovered in 2024 and ranked by WoRMS among the year's top 10 remarkable finds.
- Findings were published in Nature Communications in 2026.
- The authors caution the hypothesis rests on correlative evidence because no living specimens were available for experiments.
Researchers in Japan and China have identified a never-before-seen microscopic structure — nicknamed a “dragonball” — inside a rare deep-sea mollusc, and they argue it is the first specialized organelle devoted to chemosynthesis, the process of making food from chemical energy rather than sunlight.
The findings, published in Nature Communications in 2026, come from specimens of the divine dragon glistenworm (Chaetoderma shenloong), a worm-like mollusc that buries itself in mud around methane seeps on the seafloor. The species was first discovered in 2024 at two methane seeps in the South China Sea, and that same year the World Register of Marine Species ranked it among the top 10 most remarkable finds.
The new specimens, dug up from a methane seep in the South China Sea, revealed a digestive gland riddled with the strange compartments. Formally described as “dracosphera,” each dragonball sits inside the membranes of certain cells in the animal's digestive system and carries a name borrowed from Akira Toriyama's famous manga.
What's actually inside a dragonball?
Each one is bound by more than 20 membrane layers and houses hundreds of bacteria. Those microbes can use chemical energy, rather than sunlight, to produce organic matter — the trick that lets life survive in the pitch-dark deep sea.
The researchers compare the structures to little bacterial “farms.” DNA sequencing showed each dragonball contains only a single species of symbiotic, sulfur-oxidizing bacteria, which turn sulfur compounds into organic energy the worm can use.
Scientists already knew that some deep-sea animals house chemosynthetic bacteria in specialized cells called bacteriocytes. Dragonballs appear to be something new: compartments within those cells, unseen in other molluscs or tube worms.
"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 study authors explain.
Dragonballs, they argue, take that ancient partnership a structural step further.
Why would a worm pack bacteria into balls?
The researchers don't know yet, but they have two leading ideas.
- The farming hypothesis. Glistenworms spend most of their lives buried in seafloor sediment, where oxygen is scarce. The researchers suspect that at some point the worm breaks down some of the dragonball membranes, releasing the bacteria into the rest of the cell to be digested. That would let the animal harvest food from its cellular farms. Notably, researchers found no lysosomes — the cell's digestive sacs — inside the dragonballs themselves, which supports the idea that digestion happens elsewhere.
- The oxygen-saving hypothesis. In the oxygen-poor deep sea, sealing bacteria inside a dragonball could stop them from consuming a limited resource, leaving more oxygen for the glistenworm itself.
Both ideas remain unproven. "Due to the lack of living specimens available for experimentation, this hypothesis is primarily derived on correlative evidence and requires physiological validation," the authors admit.
In plain terms: the structures are real, but why they exist is still an educated guess.
A lucky catch off Japan
One of the molluscs in the study was serendipitously collected from a seep site near a mud volcano off the coast of Japan — a find that extends the species' known range and underscores how rarely these animals turn up. Nobody knows when researchers will find another.
The team sees broader lessons in the discovery. "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 — referring to animals that live buried in seafloor sediment.
The divine dragon glistenworm, elusive as it is, could light the way.
via sciencealert.com (Source)
More from Elena Vasquez
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Correspondent covering money, funding and market shifts around general science news at SciBeat.
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