Scientists with the Woods Hole Oceanographic Institute and the University of California, Santa Cruz, have discovered a species in the Celebes Sea that could be the missing link between species that reside solely in the seafloor's mud and those that live only in the water column. 

The Woods Hole scientists called the newly discovered creature a squid worm because it had characteristics of both species, but it has since been given the scientific name Teuthidodrilus samae. The creature is an annelid, the same phylum to which earthworms also belong.

The scientists used a remotely operated submersible to find squid worms between 9,200 feet and 9,500 feet deep (2,800 to 2,900 meters) in the basin between Indonesia and the Philippines, just 330 feet (100 meters) from the floor of the Celebes Sea. The newfound speciesappeared to be unusually abundant for creatures residing in such deep water.

About the size of the palm of a hand, the squid worm has a tapered body with a color that transitions from black to brown. The large muscles just underneath its skin, used for swimming, glow a shimmery, iridescent pink. Along the side of its body are glittery bristles that help it swim, and 10 long appendages hang off its front end — probably used for collecting food, UC Santa Cruz marine biologist Karen Osborn said.

The species is an especially exciting discovery because it could represent a missing link, or transitional species, said Osborn, who is lead author of the paper appearing in this week's issue of the journal Biology Letters.

"This is an intermediate species between the benthic ancestors — things living in the mud on the seafloor — and other species that live in the water column but never go to the floor," Osborn told OurAmazingPlanet.

squid wormStudying the newfound species could help piece together the evolutionary history of the creatures and determine which characteristics they adapted.

The Celebes Sea basin is surrounded by trenches that, Osborn said, prevent species from outside the basin from mixing with species inside the basin below about 1,500 meters. "It's really deep and isolated from the rest of the water," Osborn said. "So evolutionarily, the things down there could be really different."

The really deep sea has hardly been explored, and with the squid worm comes the hint of many more undiscovered species.

"Finding large abundant animals like this in the deep water column shows us how much we don't know about what's down there," Osborn said. "Just imagine all the other things that could be down there."

This article was reprinted with permission from OurAmazingPlanet.

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Inset photo of Teuthidodrilus samae: Laurence P. Madin/Woods Hole Oceanographic Institute