On land, worms do not get the best reputation. Often seen as plant-eating pests, or unattractive and slimy creatures, worms are not many people’s favorite animal and most people do not view them as beautiful or ecologically significant. However, all of this changes when we go underwater.
Deep-sea Scale Worms Discovered
Worms that live in the darkest parts of the ocean are often breathtaking, with vivid colors and alien behaviors. Recently four new deep-sea scale worms from the genus Peinaleopolynoe (meaning ‘hungry scale worm’ in Greek due to them being always found close to food) have been added to the Polynoidae family. Scale worms form part of a large family of scale worms with over 900 identified species. Many live in accessible areas, such as intertidal waters, however most prefer the deep ocean and hydrothermal vents. They are able to survive incredible pressures, high temperatures and acidic water. These newly discovered species have dazzlingly brilliant colors on their scales and shimmering bristles, resulting in the nickname ‘glitter worms’, with one species being named the ‘Elvis Presley’ worm after the rock star’s glittery sequin jumpsuits.
The new glitter worm species were discovered and described by a team of researchers from the Scripps Institution of Oceanography from the University of California, as well as the Paris-Sorbonne University, France. The results of their research were published in the ZooKeys journal in May 2020. The worms were located at a depth of approximately 3 700 meters (2.5 miles) within the Pescardo Basin and Monterey Canyon, Gulf of California, as well as the waters surrounding Costa Rica. The four new species include Peinaleopolynoe goffrediae (named for the marine biologist Shana Goffredi), P. mineoi (named for the father of biotechnologist Chrysa Mineo, who funded the research), P. orphanage (named for geobiologist Victoria Orphan) and P. elvisi (named after Elvis Presley), and P. orphanae was discovered near a hydrothermal vent from an underwater volcano at Pescadero Basin. Species were collected on missions between 2004 and 2019.
Despite their beautiful colors, scientists were also excited about what they found under the scales. The scientists discovered intricate branching structures that function as the worms’ lungs. The researchers suspect that these lungs have evolved to be large and complex, to allow these worms to survive within low oxygen environments.
These worms are commonly named ‘scale worms’ due to their overlapping scales. The newly discovered species have a striking appearance, with iridescent scales in purple, pink and blue colors, and shining fiber-optic-like bristles along their bodies, making them visibly gorgeous. The colors are produced by physical structures in the top layers of the scales, and the thicker those layers, the brighter the iridescent colors. In many terrestrial and marine animals, bright colors act as an attraction for potential mates, or a deterrent for possible predators. However, in the deep, dark ocean, the beauty and color of these scale worms is unlikely to be appreciated, due to many animals at this depth not having color vision. The worms themselves have no defined eyes, although it is possible that they can sense light in some other way. Eyes are metabolically expensive structures, and it is unlikely that they would evolve in areas where the sun can’t reach, unless they help with survival. Color at depths is usually due to bioluminescence – the production and emission of light by a living organism – but as far as the researchers can tell, the glitter worms do not produce their own light.
The glitter of these scale worms has therefore caused scientists to wonder if the colors on the scales have any significant function at all. One deep-sea biologist, Edith Widder, does believe that there might be some creatures that can see the worms. Some fish species – such as fish known as rattails or grenadier, are able to produce their own light (out of their derriere of all places) and may be able to observe the worms. Despite this lack of eyes to see the colors, researchers are certain that the scales themselves play a significant role, and they suspect the scales are used to protect these worms from attacks by other worms. This hypothesis is backed up by observed damage on the scales of some of the collected worms.
Instead of using their colorful exterior to attract mates, unlike many other creatures in the animal kingdom, it would appear that these scale worms use their scales to protect them from rivals. Although researchers still need to determine what causes the fighting between the worms, it may be due to competition for the limited resources found in the deep sea. The researchers were able to capture a video of the fighting between the worms. (Note: the video has been sped up x4 to make it a bit more interesting). Based on the observed almost-dancing behavior, it would appear that the worms size each other up in a back-and-forth dance movement (affectionately named the ‘jitterbug’ by the scientists), and try to get a bite in using their parrot-like beaks at the end of long proboscises. Prior to the video recording, the scientists were not certain about the notches and irregularities found on the scales of P. orphanae, and were surprised when they realized their seemingly passive worms were taking chunks out of each other.
These worms live on the seafloor, where they scavenge for resources, so it is unlikely that they are fighting over access to food. The researchers discovered the four new species feeding on a whale carcass that has sunk to the bottom of the ocean due to decay, as well as clusters of organic matter. Based on the small size of the worms, and the large size of the whale, there would be plenty of food to go around. It could be possible the worms fight over mates or even territory.
It is hard to believe that the deep sea is still one of the most unexplored areas in our known universe, and we can continue to make new discoveries of never-before-seen mysterious animals.