Death-Ball Sponge: The Carnivorous Sponge at 3,601 Meters That Abandoned Its Digestive System
In October 2025, a deep-sea robot named SuBastian photographed something strange on the Southern Ocean seafloor at 3,601 meters.
It looked like a translucent ball covered in protrusions the size of ping-pong balls, each studded with hooks almost invisible to the naked eye. Magnified, it resembles a spike-covered planet—or more precisely, a planet designed to kill.
Scientists gave it a blunt name: the death-ball sponge.
It is the most striking of 30 newly discovered species. But what excites biologists is not its shape—it is what it represents: an animal that threw away its digestive system and chose to eat meat.
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Sponges: The World's Most Harmless Animals?
First, a basic fact: sponges are animals, not plants—a fact that still surprises many. They have no mouth, no eyes, no brain, no muscles, no nervous system. They cannot even move.
A sponge lives in the simplest possible way: seawater flows in through pores, passes a filtering layer of "collar cells," where bacteria and plankton are trapped and digested, and clean water exits through a large opening at the top. One way in, one way out—that's a lifetime.
This lifestyle has one advantage: no competition needed. No chasing prey, no fighting for territory. Just stick yourself somewhere with good water flow and open your pores. Sponges have lived this way for 600 million years, making them among Earth's oldest multicellular animals—older than dinosaurs by over 300 million years.
So when you hear "carnivorous sponge," the first reaction is: you're kidding, right?
How does something without a mouth eat meat?
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1995: A Heretic in an Underwater Cave
The story begins in 1995.
That year, French marine biologists Jean Vacelet and Nicole Boury-Esnault discovered an odd sponge in a Mediterranean underwater cave. Unlike ordinary sponges, it was nearly pore-less. No collar cells, no filtering system, no water circulation channels.
In other words, it had discarded everything sponges depend on.
Yet it was alive—and thriving.
Under the microscope, Vacelet saw the truth: the sponge's surface was covered with fine filaments bearing hook-shaped spicules. Like Velcro, these hooks snag passing small crustaceans. Once prey is caught, the sponge's cells migrate onto the victim and engulf its fragments one by one—a process called phagocytosis.
This is the only known case among multicellular animals of digesting prey far larger than its own cells without any digestive chamber.
Ordinary animals eat by moving food into a cavity (stomach, gut), breaking it down with enzymes, then absorbing it. These sponges take a different path: every cell is an independent "mouth." Like ants, they collectively crawl onto prey and eat it from the outside in.
Vacelet published the finding in *Nature*. The carnivorous sponge family Cladorhizidae entered the biology textbooks.
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Why Lose a Digestive System?
This question is deeper than "how does it eat meat."
Carnivorous sponges didn't "evolve" the ability to eat meat. Quite the opposite—they first lost their filter-feeding system, and then had no choice but to eat meat.
The logic: on the deep seafloor, food is extremely scarce. Plankton are too sparse for filter-feeding to sustain life. In such an environment, maintaining a complex filtering system (collar cells, water canals, energy-hungry pumping) becomes a burden—like driving a gas-guzzling SUV in a desert.
So some sponges dropped the system. Collar cells gone, water canals gone, digestive chamber gone. They simplified to the extreme—keeping only the most basic cell structures and a set of spicules.
But losing filter-feeding meant finding new food. What is most common in the deep sea? The occasional passing crustacean. So spicules once used for filtering were remade into hooks, and cells once used for moving water became mobile digestive units.
This is not a story of "evolving superpowers"—it's a desperate counterattack after hitting rock bottom.
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Death Ball: The Perfect Hunter at 3,601 Meters
The 2025 discovery pushes this strategy to a new level.
It belongs to the Cladorhizidae family but differs in form from all previously known carnivorous sponges. Most are branch-like or candelabra-shaped—filaments stretching in all directions like a 3D net. The death-ball sponge rolled itself into a sphere.
The shape is no accident. A sphere has the smallest surface-area-to-volume ratio, maximizing capture area while minimizing energy cost. At 3,601 meters, where food is nearly nonexistent, every calorie counts.
The "ping-pong balls" aren't decoration. Each is an independent capture unit covered in transparent hook-shaped spicules. Transparency matters—transparent structures don't scare off prey in the deep sea's faint light. Small crustaceans brush against a hook and get stuck; the more they struggle, the tighter they're hooked.
Then the phagocytic cells migrate. They crawl out of the sponge, onto the prey, and each takes a bite. No stomach, no enzyme pool, no digestive tract—just thousands of cells in a silent collective feast.
The process can take days. When only the shell remains, the cells crawl back to await the next victim.
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Fellow Strangeness
The death-ball sponge wasn't the expedition's only surprise.
Near the South Sandwich Trench and its volcanic vents, SuBastian also photographed:
An iridescent scale worm — a worm found at 2,700 meters covered in color-shifting scales, like wearing a disco-ball coat. Scientists nicknamed it the "showgirl worm."
Bone-eating worms (Osedax) — also called "zombie worms." No mouth, no anus, no digestive tract. They use root-like structures to bore into whale bones, relying on symbiotic bacteria to digest the fat inside.
Starfish and black corals — new species surviving in the extreme environment near hydrothermal vents, where water temperatures reach tens of degrees and toxic sulfides abound.
What these creatures share: they all live in the most improbable ways. The mouthless eat bone; the gutless eat meat; the eyeless glow in the dark. The deep sea isn't hell—it's evolution's maddest laboratory.
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30% and 100,000
The expedition collected nearly 2,000 specimens, but scientists have analyzed only about 30%. The 30 new species are just the beginning.
Ocean Census's goal is grander: 100,000 new ocean species within 10 years. An estimated 1–2 million marine species remain undescribed—we may know the Moon's surface better than our own seafloor.
That's not hyperbole. Lunar surface maps are precise to the meter, while over 80% of the seafloor has never been explored. Every SuBastian dive may reveal something no human has ever seen.
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A Philosophy Without a Stomach
What fascinates me most about carnivorous sponges isn't the hooks or the sphere—it's the choice to abandon the digestive system.
In evolution, "losing" is harder to understand than "gaining." We're used to thinking of evolution as addition—wings, eyes, bigger brains. But carnivorous sponges show that sometimes subtraction is the real innovation.
It lost collar cells, water circulation, the digestive chamber. It simplified itself to the bare minimum—then, on that minimalist framework, rebuilt an entirely new way of eating.
One analogy: microservices aren't about adding to a monolith—they're about dismantling it and recombining smaller units. Each phagocytic cell is like an independent microservice—no central scheduler (no nervous system), no shared infrastructure (no digestive chamber), just one rule: eat when you touch food.
The analogy only goes so far. The sponge's "architecture" is extremely inefficient—cells eat one bite at a time, slower than any animal with a digestive system. But at 3,601 meters, efficiency was never the first priority. Survival is.
Sometimes the best strategy isn't getting stronger—it's getting simple enough that you need very few conditions to survive.
The death-ball sponge waited on the seafloor for untold ages before a single human robot passed by. It wasn't in a hurry. It has all the time in the world.
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*References:*
- *Vacelet, J. & Boury-Esnault, N. (1995). Carnivorous sponges. Nature, 373, 333-335.*
- *Ocean Census (2025). Carnivorous "Death-Ball" Sponge Among 30 New Deep-Sea Species from the Southern Ocean.*