''Sesarma reticulatum'', the purple marsh crab or simply marsh crab, is a crab

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

native to the

salt marsh A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is domin ...

es of the eastern United States.

Distribution

The range of ''S. reticulatum'' extends from

Woods Hole, Massachusetts Woods Hole is a census-designated place in the town of Falmouth in Barnstable County, Massachusetts, United States. It lies at the extreme southwest corner of Cape Cod, near Martha's Vineyard and the Elizabeth Islands. The population was 781 ...

Volusia County, Florida Volusia County (, ) is located in the east-central part of the U.S. state of Florida, stretching between the St. Johns River and the Atlantic Ocean. As of the 2020 census, the county was home to 553,543 people, an increase of 11.9% from the ...

; a related species occurs in the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United S ...

Description

''Sesarma reticulatum'' is purple or brown, with darker speckles, with a

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 und ...

up to long. It can be distinguished from the closely related '' S. cinereum'' by the presence of a second tooth around the orbit of each eye. The larvae or zoea of ''Sesarma reticulatum'' are aquatic, residing at a depth of greater than 1 meter below the water's surface. The larvae remain in

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 environme ...

during their development, providing food for predators.

Ecology

Their

overpopulation Overpopulation or overabundance is a phenomenon in which a species' population becomes larger than the carrying capacity of its environment. This may be caused by increased birth rates, lowered mortality rates, reduced predation or large scale m ...

, caused by over-harvesting by

recreational fishermen Recreational fishing, also called sport fishing or game fishing, is fishing for leisure, exercise or competition. It can be contrasted with commercial fishing, which is professional fishing for profit; or subsistence fishing, which is fishing fo ...

of its natural

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

s such as

blue crabs Blue crab may refer to: * Blue Crab 11, an American sailboat design * ''Callinectes sapidus'' – Chesapeake or Atlantic blue crab of the West Atlantic, introduced elsewhere * '' Cardisoma guanhumi'' – blue land crab of the West Atlantic * ''Disco ...

striped bass The striped bass (''Morone saxatilis''), also called the Atlantic striped bass, striper, linesider, rock, or rockfish, is an anadromous perciform fish of the family Moronidae found primarily along the Atlantic coast of North America. It has ...

, smooth dogfish and

cod Cod is the common name for the demersal fish genus '' Gadus'', belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus ''Gadus'' is commonly not c ...

, has been blamed for the decline in cordgrass found in the salt marshes of

Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of mainland Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer mon ...

and the decrease in the extent of

es on the Atlantic coast of North America due to increased

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is di ...

. Scientists from Brown and Princeton universities methodically ruled out other causes for the degradation of the salt marshes. The explosion in the population of sesarma crabs has provided additional food to night herons. The crabs eat marsh grass not only from above but underground in tunnels they construct. The research demonstrates the possible cumulative ecological impact of popular human activities such as recreational fishing.

References

{{Taxonbar, from=Q6497242 Grapsoidea Crustaceans of the Atlantic Ocean Crustaceans described in 1817