/ 5 January 2012

New sea creatures found living in extreme conditions

A world of previously unseen creatures has been found thriving next to boiling vents of water, several miles under the surface of the Southern Ocean near Antarctica. Hundreds of hairy-chested yeti crabs, a mysterious-looking pale octopus and colonies of limpets, snails and barnacles were found by British scientists at a hydrothermal vent located in the ocean’s East Scotia Ridge.

Professor Alex Rogers of Oxford University used a remotely operated vehicle called Isis to scout the sea bed around the ridge, which spans about 2.4km and features springs of black, smokey water that can reach temperatures of almost 400C°. The hydrothermal vents are powered by underwater volcanoes, and the scalding temperatures and rich mineral content of the water gives rise to vast rocky chimneys that support a wide variety of life forms.

“The visually dominant species are the yeti crabs, which occur in fantastically high densities, up to 600 per square metre around the southern ridge,” said Rogers, who led the expedition aboard the RSS James Cook in January 2010. “Also high densities of stalked barnacles, a large snail from a group called the peltospiroids, and we’ve also got small, green limpets which occur all over the vents.”

The first-known yeti crab, Kiwa hirsuta, was described living near a hydrothermal vent in the south pacific in 2005 and, since then, several species have been discovered in different parts of the undersea world. Around other hydrothermal vents, however, these creatures tend to occur in lower numbers; and the new species found in the East Scotia Ridge are not only more numerous but also visually distinct.

“Hirsuta has long hairs on its limbs and its claws, whereas our yeti crabs have extremely hairy chests. One of the nicknames of the crabs which developed during the cruise was the Hasselhoff crabs because they had these dense mats of [hair] on their undersides, the equivalents of their chests.”

Another striking creature spotted by the scientists was a pale octopus, which was photographed by the team. Rogers suspected it might be a new species related to the Vulcanoctopus hydrothermalis seen at other underwater vents around the world.

‘Completely different’
In total, the expedition brought back more than 12 000 samples of rocks, bacteria and animals. Rogers said: “One of the staggering things we did find is that these vents are completely different to those seen anywhere else — the animals existing at these vents are almost all new to science,” he said. The findings were published on Tuesday in the journal PLoS Biology.

“What we didn’t find is almost as surprising as what we did,” said Rogers. “Many animals such as tubeworms, vent mussels, vent crabs, and vent shrimps, which are found in hydrothermal vents in the Pacific, Atlantic, and Indian Oceans, simply weren’t there.”

Last week, scientists at the University of Southampton announced the discovery of new creatures in the so-called “Dragon Vent” in the south-west Indian Ocean.

Doctor Jon Copley, a marine biologist at the University of Southampton who led the exploration of the Dragon Vent and is also an author on the latest PLoS Biology research paper, said that exploration of the world’s deep-sea vents was a race against time.

“The exploitation of the deep ocean is overtaking its exploration. We’re fishing in deeper and deeper waters, oil and gas is moving into deeper waters and now there’s mining starting to take place in deep waters. We need to understand how species disperse and evolve in the deep oceans if we’re going to make responsible decisions about managing their resources.”

Rogers added that the vents revealed much about how deep water communities have evolved, and how they are distributed across the world’s oceans. “In the space of a single eight-week cruise, we’ve changed our level of understanding of these systems completely. We’ve changed our ideas about how vent systems are distributed and the factors that may influence that distribution. What that tells us is that our level of knowledge of the deep sea in general is extremely poor indeed.”

He added that hydrothermal vents had already changed the way scientists thought about how life exists on earth. “They told scientists that life could exist in the absence of sunlight — you could have food webs based on mechanical energy. They were also informative about the extreme conditions under which life could exist, they told us about where else in the universe life may occur. Hydrothermal vent biology has stimulated a whole new science of astrobiology.” —