Scientific Name and Authority

Carcinus maenas   (Linnaeus, 1758)


Description:

The carapace of Carcinus maenas is about 3/4 long as it is broad, with a surface finely and unevenly granular, especially in the anterior half. The front has three round lobes or teeth projecting moderately between its eyes. The anterior-lateral border is slightly arched with five strong teeth, directed forward, on each side. The claws are slightly unequal, nearly smooth except for two ridges on the upper surface of the hand. The merus ('forearm') is short, while the carpus ('wrist') has a broad internal tooth or angle. The walking legs are smooth and spineless. The fifth pair of legs is slightly flattened, but is not greatly modified for swimming. The abdomen of male C. maenas is broad and triangular, with segments 3-5 fused. The mature female has a broad abdomen, with free segments. The color is highly variable, but adults are usually multicolored with a dorsal surface ranging from dark green, grayish green, or reddish, while the undersurface is yellowish white to orange. In juveniles, the color is highly variable, often with bold contrasting colors (Williams 1984).

Zoeae and megalopae larvae of C. maenas are illustrated in Roft et al. (1984) and Johnson and Allen (2005), along with additional references on larval development, and comparisons to East Coast crab larvae. Rice and Tsukimura (2007) also provide a description, with comparisons to West Coast (San Francisco Bay) crab larvae.

Taxonomic Classification:


Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Subclass: Eumalacostraca
Superorder: Eucarida
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Brachyura
Superfamily: Portunoidea
Family: Portunidae
Genus: Carcinus
Species: maenas

Synonyms:

Cancer granulatus (Say, 1817)

Cancer moenas (De Kay, 1842)

Carcinides maenas (Rathbun, 1930)

Carcinus granulatus (Smith, 1873)

Portunus maenoides (Rafinesque, 1817)

Potentially Misidentified Species:

Carcinus aestuarii

The status of the Mediterranean Green Crab, C. aestuarii Nardo 1847 (C. mediterraneus Cziernavsky 1884), as a separate species from C. maenas, has been disputed. Morphological differences between the two species include subtle differences in shapes of spines and segments, the shape of the frontal carapace, male pleopod shape, number of segments in the flagellum, and presence/absence of setae on the chelipeds. A morphometric study by Clark et al. (2001) found some overlap between the two populations. However, Yamada and Hauck (2001) listed morphological characteristics for field separation of the two species and they found an intermediate specimen from Rabat, Morocco. Genetic studies by Bagley and Geller (2000) and Roman and Palumbi (2004) support the separation of the two species.