Bioluminescent 'Green Bombers' from the Deep Sea Discovered

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From Scripps Oceanography:

<<In the latest proof that the oceans continue to offer remarkable findings

and much of their vastness remains to be explored, scientists at Scripps

Institution of Oceanography at UC San Diego and their colleagues have

discovered a unique group of worms that live in the depths of the ocean.

(Image 1 Credit: Casey Dunn)

The discoveries feature worms nicknamed green bombers that can release

body parts that produce a brilliant green bioluminescent display.

(Image 2, with arrows showing the animal’s large bombs; Credit- Monterey Bay Aquarium Research Institute)

The discovery is described in the August 21 issue of the journal Science and

is led by Karen Osborn of Scripps Oceanography.

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. What¹s 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, we¹ve picked up seven new species. It goes to show

that we have much more exploration ahead and who knows what else we¹ll

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.

Due to the bright lights of the submersible, scientists were not able to

witness bomb-casting in the worm¹s natural habitat, but rather on ships

after the animals were captured. While the scientists speculate that the

bombs are used as a defensive mechanism against potential predators, more

studies are needed to fully understand the process.

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 there¹s a

similarity of being detachable, but for some reason the gills have

transformed to become these glowing little detachable spheres.

(Image 3: Scripps professor Greg Rouse; Credit- Scripps Institution of Oceanography, UC San Diego)

Osborn continues to probe many of the various adaptations the worms have

made since evolving into swimming species. The challenges faced by animals

living in a three-dimensional open water habitat above the seafloor are very

different than those faced by animals living on the seafloor. These include

locating new food sources, finding ways to maintain optimal depth and

grappling with predators that come from various directions.

“I¹m 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 Göteborg 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 President¹s Postdoctoral Fellowship, the David and

Lucile Packard Foundation, NOAA, WHOI and the National Geographic Society.>>

To watch three related, and very cool, videos, please go here.

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