Four new members have been added to the Polynoidae family, also known as scaleworms, or "Elvis worms". The new discoveries look like they would be more at home in a burlesque show than at the bottom of the Pacific Ocean, where they actually live.
Scale worms form an enormous family with more than 900 identified species. Some live in quite accessible locations such as intertidal waters, but most prefer to inhabit more forbidding locations, such as around hydrothermal vents, surviving enormous pressures, fearsome temperatures, and acidic waters.
University of California, San Diego student Avery Hatch and team conducted a study of the genus Peinaleopolynoe (which means "hungry scaleworm"), a deep-sea branch of the family that doesn't let living in a world without sunlight stop them putting on a show.
Hatch explored the relationships of two previously discovered Peinaleopolynoe with other members of the wider Polynidae family. In Zookeys, Hatch and co-authors describe four new species identified in the process, discovered at depths of over 915 meters ( 3,000 feet) in the eastern Pacific Ocean, including the Monterey Canyon, the Gulf of California, and Costa Rica, collected on missions between 2004 and 2019.
Peinaleopolynoe have long been nicknamed "Elvis worms" because their glittery outfits look like the sequins on the King's famous jumpsuits. Hatch and co-authors made this official by naming one Peinaleopolynoe elvisi. P. mineoi, P. orphani and P. goffredi pay tribute to Dr Ronald Mineo who helped fund these explorations, and deep-sea biologists Dr Victoria Orphan and Dr Shana Goffredi.
Food is hard to come-by down there, so in addition to surviving at vents and methane seeps where nutrients and sources of energy literally bubble up from the sea floor, P. goffredi and P. elvisi were found in a whale fall, which is just what it sounds like. Dead whales provide immense amounts of food for hungry invertebrates, although finding a new one must pose a challenge for those who have finished off the last one.
Specialists in invertebrates no doubt find many aspects of these new species, fascinating but as University of North Carolina marine biologist Dr Rebecca Helm noted on Twitter there's one question that attracts much broader interest.
One explanation is that this is a pure accident – the glitter serves no evolutionary purpose but is a side-effect of something else. On the other hand, the deep ocean is not entirely dark. Bio-luminescent creatures provide a little illumination – including as Helm notes, fish that shine lights out of their butts.
The authors noticed notches on the P. orphanae sample that were not there on the other worms, but were not sure what they were until they obtained film of the worms in their natural habitat, 2.2 miles (around 11,600 feet) down in the Gulf of California, seen here sped up four times.
"It wasn't until we saw that video of them fighting that it suddenly clicked. Like, 'Wait – these things in the scales, these notches, are bite marks,'" senior author Dr Greg Rouse said in a statement. However, Rouse and the other scientists can't explain the strange moves made by the worms the team call "jitterbugging".