Newly discovered deep-sea worm moves like a ‘living magic carpet’

The planet’s deep-sea worms survive and thrive in some pretty inhospitable places. Some are bioluminescent, glowing in regions too deep for the sun’s powerful rays to shine. Other sea worms can live surrounded by methane, one of the Earth’s most potent greenhouse gasses. Now, scientists have discovered a new species of deep-sea worm. It was found about 30 miles off of Costa Rica’s Pacific coast in an underwater methane seep. Pectinereis strickrotti is described in a study published March 6 in the journal PLOS ONE.

[Related: These newly discovered bioluminescent sea worms are named after Japanese folklore ]

Life 3,280 feet under the sea

Pectinereis strickrotti is about four inches long and its elongated body is flanked by a row of feathery, gill-tipped appendages called parapodia. Parapodia help them swim in a wavy pattern. The worms are blind, owing to the total darkness that they experience 3,280 feet under the ocean. The team believes that Pectinereis strickrotti likely has a keen sense of smell and touch to navigate this inky black world.

These deep-sea dwellers have a hidden set of robust, pincer-shaped jaws that they can thrust outwards   for feeding. While marine biologists are still not sure what they eat, they speculate that Pectinereis strickrotti may leisurely feast  on bacteria and other worms. The worms also looked red in color when lights were shone on it, likely due to its blood. 

Pectinereis strickrotti live in methane seeps. These are parts of the seafloor where this powerful greenhouse gas escapes from rocks and sediments in the form of bubbles. Unlike hydrothermal vents, methane seeps aren’t hotter than the water that surrounds them. Both are ecosystems fueled by chemical energy and not sunlight, where the tiny microbes living in them can turn methane into food. The microbes then form the base of the food web in hydrothermal vents and methane seeps, sustaining bigger creatures, including crabs, mussels, and soft-bodied polychaete worms like Pectinereis strickrotti.

This species is a member of the ragworm family, a group of about 500 species of segmented mostly-marine worms that look like a mix of an earthworm and centipede. Many species of ragworm have two distinct life stages–atoke and epitoke. As a sexually immature atoke, these worms spend most of its life on the seafloor hanging out in a burrow. In their final act, they transform into sexually mature epitokes that swim up from their homes to find mates and spawn.

Pectinereis strickrotti is also a bit unusual compared to most ragworms. It lives in the deep sea, while its kin live in shallow waters. Its parapodia are also covered with gills, where most ragworms can absorb oxygen through their parapodia without the help of fish-like gills. The males also have large spines on the end of their tails that the team believes may have to do with reproduction. 

Help from Alvin

A team from University of California, San Diego’s Scripps Institution of Oceanography, Centro de Investigación Científica y de Educación Superior de Ensenada in Mexico, Senckenberg Research Institute and Natural History Museum in Germany, and Woods Hole Oceanographic Institution (WHOI) collaborated on this discovery.

[Related: Why these sea worms detach their butts to reproduce.]

Pectinereis strickrotti was first spotted in 2009 at about 3,280 feet deep, during a dive in the HOV Alvin submersible. This human-occupied underwater exploration vehicle is operated by the WHOI and owned by the US Navy and famously played a role in helping discover the wreckage of the RMS Titanic at the bottom of the North Atlantic. 

“When we first saw it, we immediately starting asking what is was. A vertebrate? Some strange fish? We had this blurry image and that was it, but we were very intrigued,” Alvin’s lead pilot Bruce Strickrott tells PopSci. “That’s how it is down there. You see things for one minute, they’re gone, and then you talk about it.”

The team returned to the Costa Rican methane seeps in 2018. During a dive around Mound 12 of the seep, they encountered six or more individuals of the unidentified species that they first spotted back in 2009.  For an unknown reason, the sea worms were less skittish than they had been nine years earlier. Using a five-chambered vacuum canister device on Alvin that Strickrott called the “slurp gun,” the team carefully collected several specimens and enough images and video to formally describe the new species.  

“They swim slowly, but when he really wanted to move, he started to undulate almost like a living magic carpet,” says Strickrott. “The first thing that really caught my eye was just how quick it was.”

Pectinereis strickrotti is named after Strickrott, for his his piloting work that was crucial to the worm’s discovery. He says he was completely “honored and humbled” to have this new species named after him. However, this is not the only animal that bears the submersible pilot’s name. A deep-sea dwelling hagfish called Eptitretus strickrotti is also named for him.

During the 2018 expedition, the team collected three male Pectinereis strickrotti epitokes and part of one female. Tulio Villalobos-Guerrero of the Centro de Investigación Científica y de Educación Superior de Ensenada in Mexico conducted the primary anatomical analysis that was necessary to determine that this was a new species. The specimens are currently in Scripps’ Benthic Invertebrate Collection and the Museo de Zoología at the Universidad de Costa Rica. The National Science Foundation also supported this research.

“We’ve spent years trying to name and describe the biodiversity of the deep sea,” Greg Rouse, a study co-author marine biologist at the University of California, San Diego’s Scripps Institution of Oceanography, said in a statement. “At this point we have found more new species than we have time to name and describe. It just shows how much undiscovered biodiversity is out there. We need to keep exploring the deep sea and to protect it.”

Rouse and other researchers from Scripps are planning on heading back out to sea later this year to explore deep methane seeps off the coasts of Alaska and Chile.