Pinnixa faba (Dana, 1851)

Wicksten, Mary K., 2012, Decapod Crustacea of the Californian and Oregonian Zoogeographic Provinces 3371, Zootaxa 3371, pp. 1-307 : 249-250

Pinnixa faba (Dana, 1851)

( Fig. 57F, G)

Pinnotheres faba Dana, 1851: 253 .

Pinnixa faba . — Holmes 1900: 93. — Rathbun 1904: 188; 1917: 142, pl. 31, figs. 1–4, text figs. 27, 88. — Weymouth 1910: 59, text fig. 7 (part). — Schmitt 1921: pl. 40, figs. 1–4, text fig. 154. — Johnson & Snook 1927: 393. — Zullo & Chivers 1969: 72, fig.2. — Schmitt et al. 1973: 108. — Garth & Abbott 1980: 615, fig. 25.3. — Hart 1982: 234, fig. 97. — Ricketts et al. 1985: 377. — Zmarzly 1992: 682, fig. 4. — Schneider 1993: 842.— Jensen 1995: 30, fig. 41. — Campos-Gonzalez 2007: 645, pl. 323 A3.

Diagnosis. Carapace 1.5–1.9 times as long as wide, strongly convex, truncated at sides, no transverse ridge behind gastric area, anterolateral margins marked by low ridge. Orbits oval. Female more rotund than male, with bilobed frontal region. Hands of chelipeds flattened, pubescent on inner side between fingers; fingers of female short, straight, those of male curved, gaping. Male chela more robust than that of female. Pereopods 2–5 robust, carpus, propodus about equal in length; dactyl shorter than propodus, somewhat curved. Pereopod 4 longest. Dactyl of pereopod 5 reaching middle of carpus of pereopod 4. Female carapace length 11.7 m, male smaller.

Color in life. Brown to brownish red, dirty white, yellowish to pure white; see color photograph by Jensen (1995).

Habitat and depth. Usually symbiotic in mantle cavity of pelecypods, rarely gastropods, holothuroids, ascidians; in sheltered intertidal areas. A late Pleistocene fossil of this species was found in the shell of Tresus capa x (Zullo & Chivers 1968).

Range. Prince of Wales I., Alaska to Camalu Point, Baja California, Mexico. Type locality Puget Sound, Washington .

Remarks. The mantle pea crab is a common pinnotherid of intertidal habitats. It can be confused with P. littoralis . Males of P. faba have characteristic chelae in which the fixed fingers are straight and tapering to a conical apex. In P. littoralis , the fixed fingers are slightly deflexed and have excavated apices. Females of P. faba have fingers of the chelae without gapes; in P. littoralis , the fingers gape slightly when closed. Zmarzly (1992) gave further details on differentiation of P. faba from P. littorali s.