The Fish That Can Digest Wood Like a Termite

When Wood Becomes Food

Most fish nibble on plants, plankton, or other fish.

But in the dark, murky rivers of the Amazon, one strange fish breaks all the rules.

It doesn’t hunt.

It doesn’t chase.

Instead… it eats wood.

Yes, actual driftwood — bark, splinters, logs.

Meet Panaque nigrolineatus, the only known vertebrate that eats and digests wood as part of its natural diet. Sometimes called the “wood-eating catfish,” this fish is part of the loricariid family — better known as the armored catfish.

But don’t let the armor fool you. Inside, it has one of the weirdest digestive systems in the entire fish world.

Not Just Chewing — Digesting

Many fish might chew on wood out of curiosity or by accident.

But Panaque nigrolineatus actively seeks out wood, scrapes it off submerged logs using its spoon-shaped teeth, and swallows it as food.

That’s not the shocking part.

What makes this fish so fascinating is that it actually digests the wood — something very few animals on Earth can do.

Most wood is made of cellulose and lignin, two of the hardest substances for animals to break down. Even termites need special gut microbes to digest wood.

So how does a fish manage it?

The Secret Lies in Its Gut

Inside the gut of Panaque nigrolineatus lives a specialized community of bacteria and microbes that help break down cellulose — just like in termites and cows.

These microbes ferment the wood inside the gut, turning it into digestible sugars and nutrients.

But there’s a twist:

Unlike termites, this fish doesn't rely entirely on the microbes. Some studies suggest that a large portion of the wood it eats passes through undigested — like fiber.

So is it really eating wood for nutrition?

Surprisingly, yes — but only the soft, digestible parts. It may also scrape wood surfaces to collect microbes, fungi, and organic biofilm growing on the bark, which offer protein and nutrients.

In other words, it’s eating the buffet on the wood… and also munching on the table.

A Mouth Built Like a Chisel

To pull off this strange diet, Panaque nigrolineatus has a highly adapted mouth.

Its teeth are flat, hard, and shaped like miniature chisels.

Its jaw is strong enough to grind into submerged logs — slowly wearing them down over time.

Some aquarists who keep this fish in tanks report seeing wood chips at the bottom of the tank — evidence that their fish have been “eating furniture.”

But unlike destructive pests, this fish serves a purpose:

It helps break down dead wood in tropical rivers, returning nutrients to the ecosystem.

Armor on the Outside, Surprises on the Inside

Panaque nigrolineatus isn’t just weird on the inside — it also looks unusual.

It’s covered in bony plates, which give it the nickname “armored catfish.”

It has sucker-like lips that let it cling to rocks or wood, even in fast-moving currents.

Its eyes sit high on its head, and its body is often striped in black and white — making it look like a swimming zebra with scales.

In the wild, it can grow up to 40 cm (16 inches) long, and it spends most of its time clinging to submerged logs, scraping and feeding quietly.

Where It Lives

These fish are native to rivers in the Amazon and Orinoco basins — regions known for murky, slow-moving waters and plenty of dead wood.

They prefer shady spots near fallen trees, where they can hide during the day and feed when undisturbed.

Because of their unique diet and armored appearance, Panaque nigrolineatus is popular in the aquarium trade — though they require real wood in the tank to stay healthy.

Yes, even in captivity… they still eat wood.

Why It Matters

This fish challenges everything we assume about what vertebrates can and cannot eat.

Vertebrates — animals with backbones — aren’t supposed to digest wood. That job is usually left to insects, fungi, and bacteria.

But Panaque nigrolineatus shows that evolution finds strange solutions. It carved out a niche no other fish dared to enter — becoming part lumberjack, part recycler.

In doing so, it plays a crucial role in breaking down woody debris, allowing the river to breathe and life to continue.

Without this humble fish, many tropical waterways might become clogged with logs and dead matter, slowing nutrient cycling and affecting other life forms.

Still Full of Mystery

Scientists are still studying this fish to understand how much nutrition it really gains from wood.

• Is it more termite… or more herbivore?

• Does it absorb nutrients from wood directly?

• Or is it simply using wood as roughage while feeding on biofilms?

Even with decades of research, no one knows for sure.

But one thing’s clear: no other vertebrate eats wood the way this fish does.