The Death-Ball Sponge: A Carnivore With No Digestive Cavity at 3,600 Meters Deep

Forum topic · ✨步子哥 · 2026-05-30

Summary

In October 2025, the underwater robot SuBastian photographed a translucent, hook-covered 'death-ball sponge' at 3,601 meters in the Southern Ocean, one of 30 newly discovered deep-sea species. The sponge belongs to the carnivorous family Cladorhizidae, first described by Jean Vacelet and Nicole Boury-Esnault in 1995. Unlike ordinary filter-feeding sponges, carnivorous sponges lost their choanocytes, water-circulation canals, and digestive cavity entirely. Instead, hooked spicules trap small crustaceans, and migratory cells engulf the prey directly through phagocytosis, cell by cell—an unusual strategy born of extreme deep-sea food scarcity, where maintaining a filter-feeding system became too costly. The article also covers related discoveries such as the iridescent 'showgirl' scale worm, bone-eating Osedax worms, and new species from hydrothermal vents, and discusses the Ocean Census initiative aiming to find 100,000 new marine species in a decade, noting that over 80% of the seafloor remains unexplored.

The Sponge That Chose Violence: The "Death Ball" at 3,600 Meters and the Carnivore With No Digestive Cavity

In October 2025, an underwater robot named SuBastian photographed something strange on the seafloor of the Southern Ocean, 3,601 meters down.

It looked like a translucent sphere covered in ping-pong-ball-sized protrusions, each studded with hooks nearly invisible to the naked eye. Zoom in, and it resembles a planet covered in barbs—or more precisely, a planet designed to kill.

Scientists gave it a blunt name: the death-ball sponge.

It is the most eye-catching of 30 newly discovered species. But what excites biologists is not its appearance—it is what it represents: an animal that abandoned its digestive system and turned to eating meat.

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Sponges: The Most Harmless Animals on Earth?

First, a basic fact: sponges are animals, not plants. This still surprises many people—they have no mouth, no eyes, no brain, no muscles, no nervous system. They don't even move.

A sponge lives in the simplest way possible: seawater flows in through pores, passes a filtering layer of "choanocytes" (collar cells) that trap bacteria and plankton, and exits through a large opening at the top. One way in, one way out, for a lifetime.

This lifestyle has one advantage: no competition needed. A sponge doesn't hunt, doesn't fight for territory. It just glues itself somewhere with good water flow and waits for dinner. It has lived this way for 600 million years—among the oldest multicellular animals on Earth, predating the dinosaurs by over 300 million years.

So when you hear "carnivorous sponge," your first reaction is probably: you're kidding, right?

How does something without a mouth eat meat?

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1995: A Heretic in a Cave

The story begins in 1995.

That year, French marine biologists Jean Vacelet and Nicole Boury-Esnault discovered an odd sponge in an underwater Mediterranean cave. Unlike ordinary sponges, it was almost pore-less. No choanocytes, no filter system, no water-circulation canals.

In other words, it had discarded all the equipment sponges depend on.

But it was alive—and thriving.

Under the microscope, Vacelet saw the truth: the sponge's surface was covered in fine filaments bearing hooked 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 individual cells without any digestive cavity.

Ordinary animals move food into a cavity (stomach, gut), break it down with enzymes, and absorb it. This sponge takes another path: every cell is an independent "mouth." Like ants moving house, the cells collectively crawl onto the 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 Abandon the Digestive System?

This question runs deeper than "how does it eat meat."

Carnivorous sponges didn't "evolve" the ability to eat meat. Quite the opposite—they lost their filter-feeding system first, and only then had to turn to meat.

The logic: on the deep seafloor, food is desperately scarce. Plankton is too sparse for filter feeding to sustain life. In such an environment, maintaining a complex filtration system (choanocytes, canals, energy-hungry pumping) becomes a burden—like driving a 20L/100km SUV in a desert.

So some sponges dropped the system. No choanocytes, no canals, no digestive cavity. They streamlined to the extreme, keeping only basic cell structures and a set of spicules.

But losing filter feeding meant finding new food. What's most commonly available in the deep sea? The occasional passing crustacean. So spicules once used for filtering were repurposed into hooks, and cells once used for moving water became mobile engulfing units.

This is not a story of "evolving superpowers"—it's a desperate counterattack after being pushed to the edge of poverty.

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The Death Ball: A Perfect Hunter at 3,600 Meters

The 2025 discovery pushes this strategy to a new level.

It belongs to Cladorhizidae, but its form differs from all previously known carnivorous sponges. Most are branch-like or candelabra-like—fine filaments spreading in all directions like a 3D net. The death-ball sponge curls itself into a sphere.

The shape is no accident. A sphere minimizes surface-area-to-volume ratio, maximizing capture area while minimizing energy expenditure. At 3,600 meters, where food is nearly nonexistent, every calorie matters.

The ping-pong-ball protrusions aren't decoration. Each is an independent capture unit covered in transparent hooked spicules. Transparency matters too—in the deep sea's faint light, transparent structures don't scare prey away. When a small crustacean brushes a hook, it sticks; the more it struggles, the tighter it's caught.

Then the engulfing cells migrate. They crawl out of the sponge, onto the prey, one cell taking one bite. No stomach, no enzyme pool, no digestive tract—just thousands of cells conducting a silent communal feast on the prey's surface.

The process can take days. When only the shell remains, the cells crawl back and wait for the next victim.

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Fellow Strangers

The death-ball sponge wasn't the expedition's only surprise.

SuBastian also photographed other bizarre creatures near the South Sandwich Trench and volcanic vents:

Iridescent scale worm — found at 2,700 meters, covered in color-shifting scales like 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 fats inside.

Starfish and black corals — new species surviving in the extreme environment near hydrothermal vents, where water can reach dozens of degrees and toxic sulfides permeate the surroundings.

These creatures share one trait: they all live in the most improbable ways. The mouthless eat bones; those without digestive cavities eat meat; the eyeless glow in the dark. The deep sea isn't hell—it's evolution's wildest laboratory.

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30% and 100,000

The expedition collected nearly 2,000 specimens, but scientists have analyzed only 30% so far. The 30 new species are just the beginning.

Ocean Census has a grander goal: discovering 100,000 new marine species within 10 years. An estimated 1–2 million marine species remain undescribed—we may know the seafloor less well than the lunar surface.

That's not hyperbole. The Moon's surface has been mapped to meter-scale resolution, 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 spherical shape—it's the choice to abandon the digestive system.

In evolutionary terms, "losing" is harder to understand than "gaining." We tend to think of evolution as addition—growing wings, eyes, bigger brains. But carnivorous sponges show that sometimes subtraction is the real innovation.

It dropped the choanocytes, the water-circulation system, the digestive cavity. It simplified itself to the bare minimum—then, on that minimalist framework, rebuilt an entirely new way of feeding.

It reminds me of an analogy: microservice architecture isn't about adding to a monolith—it's about tearing the monolith apart and recombining smaller units. Each engulfing cell of a carnivorous sponge is like an independent microservice—no central orchestration needed (no nervous system), no shared infrastructure needed (no digestive cavity). It only needs to know one thing: eat when you touch food.

Of course, the analogy only goes so far. The sponge's "microservices" are extremely inefficient—cells engulfing one bite at a time is slower than any animal with a digestive system. But at 3,600 meters, efficiency is never the top priority. Survival is.

Sometimes the best strategy isn't to become stronger, but to become simple enough—simple enough to survive without so many prerequisites.

The death-ball sponge has waited on the seafloor for untold millennia for one robot to pass by. It isn'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.*