Prehistoric carnivorous worms dug under the Pacific Ocean

• Bobbit worms explode from tunnels on the seabed to attract prey.
• According to a new study, these worms have carnivorous ancestors of 6 feet long who dug under the Pacific Ocean.
• Researchers have found 20 million year old tunnels made by these prehistoric worms, in Taiwan.
• Visit Business Insider’s homepage for more stories.

Scientists in Taiwan noticed strange, L-shaped holes in a set of rocks eight years ago. Since the rocks once sat on the bottom of the Pacific Ocean, they thought the tunnels were made by shrimp, or perhaps octopuses. But the shape and structure of the holes do not match those made by such creatures, and the mystery lingered.

Now it’s solved: the architects behind the tunnels were 6-meter-long worms that lived about 20 million years ago, according to a study published this week. Fossil evidence helped the authors of the study find out how these predators hunted and built their submarine habitats.

According to their research, the old marine worms would lie under the sand waiting for unsuspecting prey; when fish passed by, the worms jumped out of their holes, trapped the swimmers in their gaping claws and dragged the victims under the seabed. Folded sand around the tunnel mouths indicates that the prey hit the worms’ grip hard.

The researchers also concluded that the old worms are the ancestors of the contemporary bobbie worm, which catches prey in the same way.

Wikimedia Commons

“We have known that predatory worms have been around for hundreds of millions of years, but this is the first time we can see evidence of a behavior similar to modern bobbit worms,” ​​said Ludvig Löwemark, a geoscientist at the National Taiwan University in Taipei. and one of the co-authors of the study, Insider said.

Ancient rocks reveal how these great worms lived

Thanks to Ludvig Löwemark

Löwemark’s group found the holes in sandstone rock layers in northeastern Taiwan. The rock formed between 5.3 and 23 million years ago during an era called the Miocene.

They collected hundreds of excavation samples from the Yehliu Geopark and Badouzi Coast in Taiwan and used the samples to identify the characteristics of trace fossils of the prehistoric worm tunnels. A trace fossil is a geological formation left behind by an animal that does not include the remains of the animal.

Thanks to Ludvig Löwemark

Löwemark and his colleagues think the worms that left the holes they found left them or died. The chances of finding a petrified worm are very small anyway, Löwemark said, because the soft tissue will decompose quickly after death.

But the trace fossils can still show how the old worm hunted. The scientists named the fossil Pennichnus formosae and determined that the worms built L-shaped holes that were about an inch wide and up to 6.5 feet long.

The scientists also found evidence that the sand around the mouths of the holes was disturbed, suggesting that the predator that lived in it moved quickly to an ambush of prey, and that the prey also struggled.

This is the first time scientists have found fossil evidence of an ambush predator living under the seabed.

“So far, similar trace fossils have not been reported anywhere else on earth,” Löwemark said. Though he added that “this is probably explained by the fact that scientists until now did not know what to look for.”

Thanks to Ludvig Löwemark

Since modern bobbit worms hunt in the same way as these prehistoric creatures, the authors of the study believed that they were related.

Further evidence for the idea was in the form of iron found in the rock, to the upper part of the old holes. When bobbit worms build their holes, they line it with mucus, feeding bacteria on the mucus, leaving traces of iron behind. The iron in the trace fossils thus suggests that these ancient creatures, like bobbit worms, sometimes had to rebuild portions of their holes with slime.

An ambush predator

Shahin Dashtgard

Löwemark believes that the worms that built the old holes probably looked quite like bobbit worms. However, bobbit worms can grow up to 10 feet long – much longer than the 6.5 foot long holes.

Bobbit worms live in the Atlantic, Indian and Pacific Oceans. Only a small portion of their bodies protrude from the sand. They snake their antennae into the water and wrap them like little worms to attract fish into the area. If prey comes within striking distance, then bobbit worms explode out of their tunnels, grab the fish with sharp teeth and sink back down. The jaw of the bobbit worm, or pharynx, can cut a fish in half.

Rickard Zerpe / Wikimedia Commons

According to Löwemark, the prehistoric ancestors of the bobbit worms probably had a similar diet. But it is not known what happens after bobbit worms catch their prey and drag it under the sand (so the digestion process of the old worms is also a mystery).

Luis Carrera-Parra and Sergio Salazar-Vallejo, ecologists at El Colegio de la Frontera Sur in Mexico, told Wired that they think bobbit worms sting animals with a narcotic or lethal toxin so that the prey can be “safely ingested – especially if they are larger than the worm – and then digested through the intestine. “

However, bobbit worms do not pose a threat to humans.