Human Journey

Purple Philippine River Crabs: Freshwater Species of the Week

This small river crab in the Philippines has been identified as a new species. Photo: Hendrik Freitag


Four new species of brilliantly hued freshwater river crabs have been identified, Christine Dell’Amore reported in National Geographic News.

In a published study, Hendrik Freitag of the Senckenberg Museum of Zoology in Dresden, Germany, described the small crabs, which reside on the Philippine island of Palawan. The four species are in the genus Insulamon, including Insulamon palawanense (pictured).

The crabs are between one inch (2.5 centimeters) to 2 inches (5.3 centimeters) wide. Only one other species, I. unicorn, was known in the genus, having been found in 1992.

I. palawanense seems to be widespread on the island, although the other three new species are restricted to specific creeks. All of the crabs can only live in freshwater, though they can spend a good amount of time on land, thanks to their large gill pockets.

Scientists aren’t sure why the animals are so brightly colored, although they suspect it may help them recognize each other. Interestingly, dominant males of the species take on a red color, in contrast to the purple of females and less dominant males.

Farming and development in the Philippines does threaten the crabs, who need healthy bodies of freshwater to survive. Since they cannot live in saltwater or travel long distances over land, they are especially vulnerable to loss of habitat.

Photo: Dominant male red river crab in Philippines
Dominant males of the species take on a red hue. Photo: Hendrik Freitag


Learn more about the new river crabs.


Brian Clark Howard is a writer and editor with He was formerly an editor at The Daily Green and E/The Environmental Magazine and has contributed to many publications, including,,,, Yahoo!, MSN and elsewhere. His latest book, with Kevin Shea, is Build Your Own Small Wind Power System.

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