New deep-sea limpet species reveals big secrets of the deep ocean

Far beneath the Pacific Ocean’s surface, where light fades and the pressure could crush steel, scientists came across a brand new limpet species, Pectinodonta nautilus, clinging to a piece of sunken wood. It wasn’t treasure or lost cargo – it was life.

A small community of deep-sea creatures had made the log their home, nearly 8,000 feet (2,400 meters) down.

And right there, attached to that forgotten fragment of tree, was a sea snail that had never been seen before.

New limpet: Pectinodonta nautilus

In 2023, researchers exploring the ocean near the remote Johnston Atoll came across something that stopped them cold.

A piece of wood – about 14 inches (36 centimeters) long – had landed on the seafloor, and it was covered with life. Using a robotic vehicle named Hercules, they moved in for a closer look. They weren’t expecting what they found.

The log had become an oasis in the deep sea. Dozens of pale, thick-shelled limpets – strange, oval sea snails – were clinging to the surface.

Their shells were smooth, arched, and large for their kind. Some were over an inch (2.5 centimeters) long.

Back on board the E/V Nautilus, the science team realized they had stumbled onto a brand new species.

Strange place to find Pectinodonta nautilus

These new limpets belong to a group of deep-sea mollusks that specialize in living on “wood falls” – basically sunken logs that descend to the bottom of the ocean.

Once there, the logs attract bacteria and small creatures, creating tiny ecosystems. But these habitats don’t last long. Eventually, the wood decays or gets buried in sediment.

“Wood falls are fleeting ecosystems in the deep ocean, and yet they host remarkably specialized fauna,” said Paula Rodríguez-Flores, a postdoctoral researcher in the Department of Organismic and Evolutionary Biology at Harvard University.

“Unlike the well-studied ecosystems built around hydrothermal vents and methane seeps, wood falls remain elusive, less studied in their natural setting.”

She and her team collected 79 limpets from that single piece of wood. They named the species Pectinodonta nautilus, after the ship that helped them find it.

Closer look under the limpet shell

Back in the lab, the team used advanced scanning tools to study the limpets in fine detail. They didn’t cut them open. Instead, they used 3D models built from micro-CT scans to examine their insides.

These limpets weren’t just bigger than expected – they were built differently too. Electron microscopes showed unique features in the shell, especially a faint pattern near the back. But what really set Pectinodonta nautilus apart was its mouth.

Like other limpets, this one has a radula – a strip of teeth made from chitin, a material that is also found in insect shells. But these teeth were huge compared to its relatives.

Each one looked like an upside-down V, with about 17 sharp cusps. Compared to a close cousin called P. mazuae, the new species had nearly double the radular size.

That might mean it feeds differently. Or it might have adapted to the unique bacteria growing on this specific type of log. Either way, it showed that even among similar species, the differences can be big.

Confirming the limpet species

To confirm that this was a separate species, the team ran DNA tests and looked at the mitochondrial genome – the genes that are responsible for producing energy in the cell.

The analysis showed Pectinodonta nautilus is a distinct branch in its family tree, but it shares a close connection to other species near New Zealand and the Western Pacific.

“Our findings suggest this lineage of wood-fall may be far more widespread across the Pacific than previously recognized,” said Gonzalo Giribet, professor in OEB and director and curator of invertebrates in the Harvard Museum of Comparative Zoology.

The bigger picture is still unclear, though. The team found major gene shuffling across this group of limpets, which makes it hard to map out their full evolutionary story. They’ll need more complete genome data to figure that out.

One thing they did notice was that radular teeth seem to be a more reliable way to tell these species apart than shell shape, which can vary a lot.

An island for generations

What made this find even more remarkable was the range of sizes among the limpets. Some were tiny. Others were fully grown. That means the log hadn’t just attracted a few individuals – it supported multiple generations.

Even in one of the harshest environments on Earth, a 14-inch (36 centimeter) piece of wood had created a home. It was a temporary one, sure. But it was lasted long enough for creatures to grow, reproduce, and spread.

“The discovery underscores how little is known about life in the deep sea,” said Rodríguez-Flores. “Fewer than seven percent of described marine species come from below 1,000 meters, leaving vast stretches of ocean biodiversity unexplored.”

Lessons from Pectinodonta nautilus

The team faced challenges. The radulae – those delicate tooth structures – were fragile and sometimes broke during cleaning.

There wasn’t much tissue to work with for DNA sequencing. And it’s hard to compare species when there’s hardly anything else like them in museum collections.

But Pectinodonta nautilus isn’t the only discovery. The Nautilus team has already found several new species near Johnston Atoll, including an unknown squat lobster named Munidopsis giribeti, in honor of Professor Giribet.

“Every deep dive reveals that the ocean still holds countless surprises,” Rodríguez-Flores said. “We’re only just beginning to understand the hidden biodiversity living on the seafloor.”

The full study was published in the journal Molluscan Research.

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