''Rhithropanopeus harrisii'' (common names include the Zuiderzee crab, dwarf crab, estuarine mud crab, Harris mud crab, white-fingered mud crab, and white-tipped mud crab) is a small

omnivorous An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize ...

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

native to Atlantic coasts of the Americas, from

New Brunswick New Brunswick is a Provinces and Territories of Canada, province of Canada, bordering Quebec to the north, Nova Scotia to the east, the Gulf of Saint Lawrence to the northeast, the Bay of Fundy to the southeast, and the U.S. state of Maine to ...

Veracruz Veracruz, formally Veracruz de Ignacio de la Llave, officially the Free and Sovereign State of Veracruz de Ignacio de la Llave, is one of the 31 states which, along with Mexico City, comprise the 32 Political divisions of Mexico, Federal Entit ...

. ''R. harrisii'' is usually found in

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

water, but can also be found in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

. It likes to live on stones and in oyster beds. The crab can reach a maximum size of . It has an olive-green-brownish color, sometimes with dark spots on its

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

. It is a common inhabitant of

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

and

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

, but was later introduced all over the world. In 1937, it was discovered to be invading the

San Francisco Bay San Francisco Bay (Chochenyo language, Chochenyo: 'ommu) is a large tidal estuary in the United States, U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the cities of San Francisco, California, San ...

's brackish waters and adjacent fresh waters of the

California Central Valley The Central Valley is a broad, elongated, flat valley that dominates the interior of California, United States. It is wide and runs approximately from north-northwest to south-southeast, inland from and parallel to the Pacific coast. It cover ...

. 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 The Panama Canal () is an artificial waterway in Panama that connects the Caribbean Sea with the Pacific Ocean. It cuts across the narrowest point of the Isthmus of Panama, and is a Channel (geography), conduit for maritime trade between th ...

. ''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. In the

British Isles The British Isles are an archipelago in the Atlantic Ocean, North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner Hebrides, Inner and Outer Hebr ...

, ''R. harrisii'' has only been observed in

Roath Docks Roath () is a district and community to the north-east of the city centre of Cardiff, capital of Wales. The area is mostly covered by the Plasnewydd electoral ward, and stretches from Adamsdown in the south to Roath Park in the north. Descrip ...

, Cardiff, which have lower

salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...

(12

‰ The phrase per mille () indicates parts per thousand. The associated symbol is , similar to a per cent sign but with an extra zero in the divisor. Major dictionaries do not agree on the spelling, giving other options of per mil, per mill, pe ...

) than the surrounding waters. Breeding freshwater populations have been found in the

Brazos River The Brazos River ( , ), called the ''Río de los Brazos de Dios'' (translated as "The River of the Arms of God") by early Spanish explorers, is the 14th-longest river in the United States at from its headwater source at the head of Blackwater ...

basin in Texas, notably the Possum Kingdom State Park and Lake Granbury. Populations have also been discovered in

Lake Texoma Lake Texoma is one of the largest reservoirs in the United States, the 12th-largest US Army Corps of Engineers' (USACE) lake, and the largest in USACE Tulsa District. Lake Texoma is formed by Denison Dam on the Red River in Bryan County, Oklah ...

and Lake E.V. Spence. Its presence in the Baltic Sea is blamed for a negative ecosystem shift. A record of this species was made in Brazil, but might represent a misidentification.

References

{{Taxonbar, from=Q228637 Xanthoidea Crabs of the Atlantic Ocean Crustaceans of Brazil Crustaceans described in 1841 Taxa named by Augustus Addison Gould