On January 13, 2025, an iceberg the size of Chicago—designated A-84—broke away from the George VI Ice Shelf in Antarctica. Beneath 150 meters of ice, a world never seen by human eyes was exposed. Scientists rushed in remote-operated vehicles, and the ROV's lights pierced the darkness—
They saw sponges. Massive, flourishing sponge communities, some individuals large enough to suggest they had lived there for decades or even centuries. Corals, icefish, giant sea spiders, octopuses—a complete ecosystem thriving under the ice, as if the outside world were irrelevant.
But that wasn't today's star. What truly made scientists gasp was a discovery from another Southern Ocean expedition: a round, barbed little ball extending branching arms from a rock, slowly waving in the darkness.
It's called the "Death-Ball Sponge." It belongs to the genus *Chondrocladia*—an entire genus of carnivorous sponges.
Wait, aren't sponges... filter feeders?
Yes, the vast majority of sponges are filter feeders. They are among the oldest multicellular animals on Earth, dating back some 600 million years. They have no brain, no nervous system, no digestive organs—not even true tissues. Just a loosely coordinated mass of cells. Seawater flows in through tiny pores, choanocytes use flagella to create water currents, filtering out bacteria and organic debris, which then exits through larger openings. A basketball-sized sponge can filter thousands of liters of seawater per day.
That's a sponge's "normal" life. Quiet, passive, harmless.
But the family Cladorhizidae didn't get that memo.
This family contains 9 genera and over 175 known species—all of them carnivorous. Not the occasional snack, not facultative predation: they have completely abandoned filter feeding and rebuilt their entire body structure into hunting machines. This is nearly unique in the animal kingdom—an entire family collectively rebelling against a 600-million-year-old ancestral diet.
How does an animal with no organs eat meat?
To appreciate how bizarre this is, consider how "crude" a sponge's body is.
You and I have a complete digestive system: mouth → esophagus → stomach → intestine → anus. Food travels one line, enzymes break it down along the way, nutrients are absorbed en route. That's the standard setup for animals, from earthworms to blue whales.
Sponges have none of it. They don't even have a digestive cavity.
So how does *Asbestopluma hypogea*—a carnivorous sponge living in Mediterranean caves—eat a crustacean?
Scientists at the French Research Institute for Exploitation of the Sea (Ifremer) recorded the whole process with high-speed photography, arguably nature's eeriest feeding ritual:
Step 1: Hook. The sponge extends slender filaments densely covered with micro-barbs called "equianchorate spicules." These spicules are only tens of micrometers long but exquisitely shaped like miniature three-pronged anchors. Once a shrimp or copepod is pushed onto the filaments by the current, the barbs embed in its exoskeleton—and the more it struggles, the tighter it gets.
Step 2: Encase. Within hours of capture, cells begin migrating from all over the sponge toward the capture point. These cells—not specialized digestive cells, just ordinary wandering cells—gather in layers around the prey, gradually enveloping it completely to form a sealed "digestion pouch."
Step 3: Digest. Once enclosed, the cells secrete digestive enzymes that break down the prey's tissues from the outside in. No stomach, no intestine—just cells performing "external digestion" directly on the prey, then absorbing the nutrients.
Step 4: Clean up. The whole process takes 8 to 10 days. When digestion is complete, the cells disperse, leaving behind an empty shell of exoskeleton.
Eight to ten days. Think about how long it takes you to digest one meal.
That's the cost of having no digestive system: you don't need a stomach, but you need patience. In the food-scarce deep sea, one successful hunt can sustain you for a long time. Being slow isn't a problem—the key is not missing anything.
Death balls, harps, and ping-pong tree sponges
The carnivorous sponges of Cladorhizidae have evolved stunning diversity in "how to hook prey":
Death-Ball Sponge (*Chondrocladia* sp. nov., discovered 2025) — a spherical body with branching arms tipped in barbed bulbs, waving slowly in the dark like a slow, patient catcher. With no sunlight and no vision in the deep sea, prey relies on luck—or rather, on running into the barbs.
Harp sponge (*Chondrocladia lyra*, discovered 2012) — living 3,300 meters off the California coast, its body resembles a harp: horizontal bars with vertical branches covered in barbs. Prey pushed by deep-sea currents into the "strings" gets hooked on contact. Even more elegant: the harp sponge's spherical structures double as reproductive organs—hunting and reproduction share the same hardware.
Ping-pong tree sponge (*Chondrocladia lampadiglobus*) — slender stalks topped with strings of translucent bulbs, like a deep-sea tree decorated for Christmas. Each bulb's surface bristles with barbs, swaying gently in the current.
Their shared strategy: maximize surface area, minimize energy expenditure. In the deep sea, food density is extremely low, and filter feeding requires constant energy to maintain water flow. Carnivory only requires "waiting"—extend an arm, open the barbs, wait. It's an extreme energy-saving strategy: converting "active foraging" into "passive ambush."
Without nerves, how does it know prey has arrived?
This is the most puzzling part.
A Venus flytrap has trigger hairs—a fly touches them twice, and the leaves snap shut in 0.1 seconds—a rapid response with a clear signaling pathway. But carnivorous sponges have no nervous system, no sensory cells, no known signaling mechanism.
Their "hunting" is entirely mechanical: the barbs are a physical structure. Prey that touches them gets caught; the sponge doesn't need to "know" anything. It's like laying a mousetrap—you don't need to watch it; a mouse that steps on it gets stuck.
But the "digestion" phase is different. Cells migrating from all over the body to surround the prey requires some coordination mechanism—how do the cells know where the prey is? Which direction to move?
Current research suggests it may be driven by chemical signals: hooked prey releases chemicals (injured crustaceans leak bodily fluids), and the sponge's wandering cells detect the concentration gradient and migrate along it. It's an extremely primitive sense of "smell"—no nose, no olfactory receptor proteins (at least none found yet), but cell-level chemotaxis is enough to get the job done.
Interestingly, although sponges have no neurons, they do possess synapse-related genes. A 2007 study found that sponge genomes encode postsynaptic density proteins (PSD proteins)—key components of neuronal synapses. Sponges didn't use these genes to build a nervous system, but they may use these proteins for some more primitive form of intercellular communication.
In other words, the sponge has all the parts needed to build a nervous system—but chose a different path.
Glass sponges: telegraphy without nerves
Speaking of sponge communication, another oddity deserves mention: glass sponges (Hexactinellida).
A glass sponge's body isn't made of independent cells but is one giant syncytium—all cells are fused, sharing cytoplasm in a continuous "super cell." This means electrical signals can propagate freely throughout the body, no synapses or nerve fibers required.
In 1997, Canadian scientists discovered that when you touch a glass sponge, its choanocytes stop beating their flagella within 20 seconds—the entire body's feeding current halts simultaneously. It's a body-wide response via electrical signal conduction. The speed doesn't compare to true neural conduction (a few centimeters per second vs. tens of meters per second), but for an organism with no nervous system, it's a form of "telegraphy."
Glass sponges and carnivorous sponges took two completely different paths: one achieved body-wide coordination with electrical signals, the other local responses with chemical signals. But both prove the same point—you don't need a nervous system to mount a coordinated response.
Convergent evolution: plants and animals reaching the same solution
The convergent evolution of carnivorous sponges and carnivorous plants (like the Venus flytrap and pitcher plants) is one of the most elegant case studies in evolutionary biology.
They faced the same problem: the environment contained too few nutrients. Venus flytraps grow in nitrogen-poor swamps; carnivorous sponges live in food-scarce deep seas. Their solution was the same: switch from "waiting for manna from heaven" to "setting your own traps."
But their implementations differ completely:
- The flytrap has touch, motion, and rapid response (snapping shut in 0.1 seconds), relying on the plant-specific turgor-pressure mechanism
- The carnivorous sponge has no touch, no motion, no rapid response, relying purely on physical barb structures and chemotaxis
Even more interesting: both underwent "organ simplification." The flytrap's leaves became traps, with photosynthesis demoted; carnivorous sponges abandoned their filter-feeding apparatus—the aquiferous system regressed, replaced by hunting filaments and barbs.
When environmental pressure is strong enough, simplification beats complexification. This rule holds in both biology and engineering.
Lessons from beneath the ice
Back to Antarctica.
The thriving ecosystem under the George VI Ice Shelf had existed there for decades, perhaps centuries. Those giant sponges grow less than two centimeters a year—their size tells us they've lived under the ice shelf a long time. The ice shelf collapse didn't "create" life; it "revealed" it.
The discovery of the Death-Ball Sponge reminds us of something else: we may understand less than 10% of the deep ocean. Scientists with the Ocean Census project say they've analyzed less than 30% of the samples from that expedition and have already confirmed 30 new species. What else is hiding in the remaining 70%?
An organism with no brain, no nerves, no organs has, over 600 million years, independently invented carnivory, barbed traps, cavity-free digestion, and retained synapse-related genes without using them to build a nervous system. It isn't "primitive"—it's "another solution."
When we design AI systems, we tend to bolt on perception modules, decision modules, and execution modules—like assembling a nervous system. But sponges teach us: coordination doesn't require a central controller, response doesn't require a signaling pathway, and intelligence doesn't require a brain. Sometimes the best design lets each component respond to local information on its own, with global order emerging from local interactions.
That Death-Ball slowly waving its arms in the deep sea may be "smarter" than we imagine—only its intelligence is written in the geometry of its barbs, not in the firing patterns of neurons.
*Source: original post on zhichai.net.*