New freshwater crab described

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Scientists in Taiwan have found a new species of freshwater crab in a lake 748m above sea level, thanks to the effects of a hydroelectric power plant.

The new species, which has been named Geothelphusa leeae, has recently been described by Jhy-Yun Shy of the National Penghu Institute of Technology in a paper in the Raffles Bulletin of Zoology.

The new freshwater potamid crab was found in Sun-Moon Lake in Nantow County, central Taiwan, and is one of 35 species of crab found in the country.

Only two other crab species, Candidiopotamon rathbunae and Geothelphusa candidiensis are known to occur near Sun-Moon Lake, with both being found in influent streams, rather than in the Lake itself.

Shy says that the new crab is unusual among Taiwan's native freshwater crab species in that it's the only known species to live in a lake. The species may have gone unnoticed until now because it appears to spend the day in deep water, and only travels into the shallows at night.

Tidal lakeOddly, Sun-Moon Lake experiences a sort of artificial daily tide in which the water level drops during the day due to a hydroelectric power plant on the banks of the high altitude lake.

Says Shy: "During the day, water is allowed to flow out of conduits into a lower altitude pond to generate hydroelectric power, and the water level gradually decreases.

"At about midnight, the company utilises excess electric power to pump the water from this pond back up to Sun-Moon Lake, and the water level rises back up.

"Under these special conditions, we have been able to find G. leeae only at midnight (ie. at lowest tide). At this time we can also find many burrows along the banks which we believe to have been dug by these crabs."

For more details on the new crab species see the paper: Shy, JY (2005) - A new species of freshwater crab from the genus Geothelphusa Stimpson, 1858 (Crustacea, Decapoda, Brachyura, Potamidae) from Taiwan. The Raffles Bulletin of Zoology, 2005, 53(1).