Greg Rouse, a marine biologist at UC San Diego’s Scripps Institution of Oceanography, and other researchers have discovered a new species of deep-sea worm living near a methane seep some 50 kilometers (30 miles) off the Pacific coast of Costa Rica. 

The worm, named Pectinereis strickrotti, has an elongated body that is flanked by a row of feathery, gill-tipped appendages called parapodia on either side, and Rouse said its sinuous swimming reminded him of a snake. 

The deep-sea worm is a 10-centimeter-long (4-inch) member of the ragworm family (Nereididae). Ragworms are a group of around 500 species of segmented, mostly marine worms that look a bit like a cross between a centipede and an earthworm. They have elongated bodies with rows of bristled parapodia on their sides and a hidden set of pincer-shaped jaws that can be extruded for feeding. Many species of ragworm also have two distinct life stages: atoke and epitoke. In these species, the worm spends most of its life on the seafloor, often in a burrow, as a sexually immature (atoke), but in their life’s final act they transform into sexually mature epitokes that swim up off the bottom into the water column to find mates and spawn.

The team was able to collect three male Pectinereis strickrotti epitokes and part of one female. Following their successful collection, the team used the specimens to conduct anatomical analysis and to study the worm’s DNA to establish its evolutionary relationships within the ragworm family. The specimens now reside in Scripps’ Benthic Invertebrate Collection and the Museo de Zoología at the Costa Rica University.

Compared to most ragworms, Pectinereis strickrotti is unusual in several ways. First, it lives in the deep sea, while the majority of its evolutionary kin inhabit shallower waters. Second, its parapodia are covered in gills, while most ragworms absorb oxygen through their parapodia without the aid of true gills. The males had large spines at the end of their tails, which Rouse said might have something to do with reproduction but would require further study. Finally, owing to the total darkness at 1,000 meters (3,280 feet) under the sea, the new species is blind. Rouse said the worms probably have keen senses of smell and touch to help them navigate their inky world.

Pectinereis strickrotti has robust, even fearsome-looking jaws, but Rouse said their diet is still unknown and that the species could just as easily be feeding on bacteria as larger fare like other worms. Though its coloration would be a moot point in life, given its pitch-black habitat, Rouse said the worm appeared rosy under Alvin’s lights, and that this was probably due to the color of its blood. 

“We’ve spent years trying to name and describe the biodiversity of the deep sea,” said Rouse. “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.”

The species was named after Woods Hole Oceanographic Institution’s Bruce Strickrott, lead pilot for the famed deep-sea submersible Alvin, who Rouse said was instrumental in the effort to locate and collect the creature. The research was supported by the National Science Foundation.