Rhithropanopeus

Rhithropanopeus harrisii (common names include the Zuiderzee crab,<ref name="JNCC">Template:Cite web</ref> dwarf crab,<ref name="JNCC"/> estuarine mud crab,<ref name="USGS"/> Harris mud crab,<ref name="USGS"/> white-fingered mud crab,<ref>Template:Cite web</ref> and white-tipped mud crab) is a small omnivorous crab native to Atlantic coasts of the Americas, from New Brunswick to Veracruz.<ref name="JNCC"/>

R. harrisii is usually found in brackish water, but can also be found in freshwater. It likes to live on stones and in oyster beds. The crab can reach a maximum size of Template:Convert. It has an olive-green-brownish color, sometimes with dark spots on its carapace.

It is a common inhabitant of Texas and Florida estuaries, but was later introduced all over the world.<ref name="USGS">Template:Cite web</ref> In 1937, it was discovered to be invading the San Francisco Bay's brackish waters and adjacent fresh waters of the California Central Valley.<ref name="USGS"/> It was also recently discovered in the Third Lock Lake in Panama, a man-made lake intended to be a part of the Panama Canal.<ref>Template:Cite journal</ref>

R. harrisii was first discovered in Europe in the Zuider Zee, the Netherlands, and is now also found in Denmark, Belgium, Germany, France, Poland, Estonia, Finland, Russia, Portugal, Spain, Italy, Romania and Bulgaria, from the Black Sea and Caspian Sea.<ref name="JNCC"/><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

In the British Isles, R. harrisii has only been observed in Roath Docks, Cardiff, which have lower salinity (12‰) than the surrounding waters.

Breeding freshwater populations have been found in the Brazos River basin in Texas, notably the Possum Kingdom State Park and Lake Granbury. Populations have also been discovered in Lake Texoma and Lake E.V. Spence.<ref>Template:Cite journal</ref> Its presence in the Baltic Sea is blamed for a negative ecosystem shift.<ref>Template:Cite journal</ref>

A record of this species was made in Brazil, but might represent a misidentification.<ref>Template:Cite journal</ref>