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發表於 2011-11-25 10:28 AM
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[貼圖] New Deep-Sea Worms Found—Have Big "Lips"
Seafloor "Flower"
Lying like a flower on the seafloor, this newfound acorn worm has a color that poses an intriguing question for scientists.
"Why this brilliant purple, the dark reds, these amazing colors at depths where there is no light? I can't tell you," Osborn said.
"We see brilliant purples and reds [in other worm species] at depths of 500 or 1,000 meters [1,640 or 3,280 feet] where there is very little light, because [such colors] look black there, so those colors are great camouflage.
"But here, where there is no light at all except that produced by organisms, there seems no reason to spend energy making yourself these colors when nothing can see them.
"There is a reason," Osborn added. "We just have to figure out what it is."
Expert Floaters
A recently discovered species of acorn worm floats in the water column, one of the survival abilities the creatures have developed for life in the deep.
The worms' delicate, gelatinous bodies allow them to easily float up to 65 feet (20 meters) above the seafloor as well as to move around in search of food—an ability that initially shocked scientists.
"I wouldn't call it swimming but controlled floating. They use their gut contents as ballast," Osborn said.
"They empty their guts of sediment and sand and then make mucous balloons that help to lift them off the bottom. Once up, they very rigidly hold specific postures, the way they float best, and then to come down they release the mucous balloons and straighten up their bodies again."
Living Fossil
In an evolutionary sense, acorn worms (pictured, a newfound species) are living fossils—part of a little-known group that may bridge the gap between invertebrates and the first vertebrate animals.
Acorn worms belong to a phylum that is considered the most closely related to the chordates—backboned animals—a group that includes birds, fish, humans, and many other vertebrate species, Osborn explained.
"Understanding the acorn worms' group better helps us understand what the earliest chordates probably looked like, because this group and the chordates probably came from the same ancestor."
Zigzag in the Sand
A feeding acorn worm leaves a distinctive zigzag trail in the seafloor sediment. Such patterns helped scientists discover the animals and realize their importance to the seafloor ecosystem, Osborn said.
"We've looked through a bunch of video from other underwater vehicles, and every ocean basin has these little trails that [the worms] leave," she said.
Scientists spotted acorn worms as early as the 1970s, but the gelatinous animals were too fragile to collect from the seafloor.
During the past decade, advances in remotely operated vehicles and imaging technology allowed scientists to not only identify new acorn worm species but also to observe how they behave.
One of Many
The new study confirms that the previously recorded acorn worm seen above is in fact a new species. Many more new acorn worm species are probably waiting to be found in the world's seas, Osborn said.
"It's a great example of how much we still need to learn about the oceans," she said.
"We're having major impacts on the oceans, from global warming to pollution to overfishing, and we don't even know what major groups of animals are living down there." |
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