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Scientists document rare catfish climbing a near-vertical cave wall to reach food


Climbing catfish

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(NaturalNews) In what might be a first, scientists have filmed a species of catfish climbing the nearly vertical walls of a cave far from the stream below, according to a paper published in the journal Subterranean Biology.

"As part of a mapping and preliminary flora and fauna inventory of hypogean life in caves, developed in Cretaceous limestones in the sub-Andean zone of Ecuador, we were able to observe a number of catfish climbing a steep flowstone waterfall in the dark zone of a cave," the researchers wrote.

Although catfish have previously been known to climb walls, this marks the first time such behavior has been observed in a cave. The researchers said that the behavior might be a sign of evolution taking place as a normally surface-dwelling fish adapts to a new environment.

Ten feet above nearest water source

The catfish were tentatively identified as Chaetostoma microps, a members of the armored catfish family (Loricariidae) native to surface rivers in the upper Amazon basin, including the region where the fish was filmed.

Many catfish in the Loricariidae family have previously been observed climbing waterfalls and other nearly vertical streams, but only one species has been known to do so in caves. In addition, other catfish remain in water sources while climbing; the Ecuadorian fish was climbing on walls roughly 10 feet above the stream below.

"It's not too surprising to find another catfish that climbs rocks," Scientist Geoff Hoese said. "What is surprising is the environment that they are doing it in."

The fins, skin and mouth of climbing catfish have all been modified to give them their unusual abilities. Hoese and his colleagues believe that the Ecuadorian catfish was able to use its climbing abilities to leave the stream entirely because there was still a tiny amount of water trickling down the cave wall.

"The thin film of water flowing over them as they climb likely provides pressure to help hold them to the wall, and these various structures help keep them from sliding down," Hoese said. "They can then wriggle their way up, or also down, as you can see in the video."

Evolution at work?

If the climbing catfish's identity as C. microps is confirmed -- the researchers were not authorized to collect specimens from the cave, so they could not make a positive identification -- it poses a serious scientific puzzle. That's because C. microps is only known to live above ground.

"This species is known to primarily eat algae, and as there's no sunlight in the caves, there's not much algae, so it seems unlikely that they are there to feed," Hoese said.

In addition, the fish observed did not have any of the characteristics that would be expected of fish adapted to cave life, such as colorlessness or blindness.

"This is a significant observation that merits investigation into why they are there," Hoese said.

One possibility is that the fish merely have a tendency to explore their entire range, and they sometimes stray into unsuitable habitats. The fish might also have an instinct to head upstream, such as for breeding, which could sometimes lead them underground.

Another possibility is that the fish filmed are in the process of adapting to underground life, but they have not had time to develop colorlessness, blindness or other associated traits.

"Evolution is a process that's constantly at work," Hoese said. "It's interesting to look at examples where there may be changes, such as here, where we have a surface fish exhibiting specific behaviors and occupying an unusual habitat."

"There isn't enough data at this point to do more than speculate, but it's nice to think that we may be watching a small but significant evolutionary step as a species moves from one niche to another," he said.

(Natural News Science)

Sources:

http://www.dailymail.co.uk

http://news.nationalgeographic.com

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