Bioluminescent 'Green Bombers' Discovered in the Deep Sea
Orbs lobbed by mysterious worms burst into brilliant light
|The transparent body of the worm Swima bombiviridis allows examination of internal anatomy without dissection. The purple arrow points to the several bioluminescent bombs still attached to the segments immediately behind the head. Courtesy of Casey Dunn|
The researchers introduce seven previously unknown species of swimming worms in the annelid phylum ranging from 18 to 93 millimeters (.7 to 3.6 inches) in length. They were discovered by the scientists using remotely operated vehicles at depths between 1,800 and 3,700 meters (5,900 and 12,140 feet). The first species described in the paper has been given the scientific name Swima bombiviridis, referring to its swimming ability and the green bombs.
Osborn says one key aspect of the discoveries is that the newly found worms are not rare. Opportunities to witness such animals and collect and study them, however, have been extremely rare.
"We found a whole new group of fairly large, extraordinary animals that we never knew anything about before," said Osborn, a post-doctoral researcher in the Marine Biology Research Division at Scripps. "These are not rare animals. Often, when we see them, they number in the hundreds. What's unique is that their habitat is really hard to sample."
Largely transparent except for the gut area, the worms propel themselves with fans of long bristles that form swimming paddles.
"The depths between 1,000 and 4,000 meters (3,280 and 13,120 feet) form the biggest habitat on Earth and also the least explored," said Scripps Professor Greg Rouse, a coauthor of the paper and curator of Scripps Benthic Invertebrate Collection. "With fairly limited time on submersible vehicles, mainly off California, we've picked up seven new species. It goes to show that we have much more exploration ahead and who knows what else we'll discover?"
Each of the species features a variety of elaborate head appendages. Five of them are equipped with luminescent structures, the "bombs," that are fluid-filled spheres that suddenly burst into light when released by the animal, glowing intensely for several seconds before slowly fading.
|A video image of a species of Swima (as yet undescribed) with arrows indicating the animal's large bombs. Courtesy of Monterey Bay Aquarium Research Institute|
Rouse says the green bombers in the newly discovered clade, (a common ancestor and all its descendant organisms), are fascinating from an evolutionary standpoint. Looking closely at their relatives that live on the seafloor, it appears the bombs were once gills that evolutionarily transformed over time.
"The relatives have gills that appear to be in exactly the same places as the bombs," said Rouse. "The gills can fall off very easily so there's a similarity of being detachable, but for some reason the gills have transformed to become these glowing little detachable spheres."
|One of the first green bombers (Swima bombiviridis) collected from Monterey Bay and photographed by Steven Haddock of the Monterey Bay Aquarium Research Institute. Several green bombs are visible near the animal's long coiled head palps.|
"I'm interested in how animals have evolved in the water column," said Osborn. "These worms are great examples. How does a worm transform into a wonderful glowing animal?"
In addition to Osborn and Rouse, coauthors of the Science paper include Steven Haddock of the Monterey Bay Aquarium Research Institute, Fredrik Pleijel of the University of Goteborg in Sweden and Laurence Madin of the Woods Hole Oceanographic Institution (WHOI). The research was supported by Scripps Institution of Oceanography, a University of California President's Postdoctoral Fellowship, the David and Lucile Packard Foundation, NOAA, WHOI and the National Geographic Society.