Pacifastacus leniusculus (Dana, 1852)

Wicksten, Mary K., 2012, Decapod Crustacea of the Californian and Oregonian Zoogeographic Provinces 3371, Zootaxa 3371, pp. 1-307 : 126

Pacifastacus leniusculus (Dana, 1852)

( Fig. 30D–F, L)

Astacus leniusculus Dana, 1852: 524 . — Stimpson 1857b: 493. — Hagen 1870: 94. — Holmes 1900: 166. — Bonnot 1930: 212, figs. 65–67.

Pacifastacus leniusculus . — Riegel 1959: 39, fig. 1F–H, fig. 3A, 6. — Miller & Van Hyning 1970:77, figs. 1, 2. — Abrahamsson & Goldman 1970: 83. — Hobbs 1976: 21, figs. 5a,12 a–c, 14e. — Eng & Daniels 1982: 200, fig. 1a. — McGriff 1983: 227. — Kuris et al. 2007: 636. — Larson & Olden 2011: 64, p. 61 figs. C, D.

Diagnosis. Rostrum acute, with single pair marginal teeth or tubercles, with or without median carina, with dorsal surface depressed. Postorbital ridges rounded or with pair of teeth or tubercles. Carapace with prominent cardiac grooves, paired branchiocardiac grooves, branchial regions slightly to greatly inflated. First antennae small, peduncle about same length as rostrum. Basicerite of second antenna with sharp lateral tooth. Scaphocerite with acute lateral tooth, as long as or slightly longer than rostrum. Third maxilliped setose, ischium armed with sharp spines on mesial, lateral margins of distal margin (forming "crista dentata"), next segment armed with spinules. Major chelae with smooth to tuberculate surface. Length of fingers about 3 times as long as length of palm, fixed finger with low tooth on cutting edge near proximal end. Outer margin of palm convex, inner convex, flared proximal to dactyl. Inner margin of palm with crest, slight depression parallel to crest on inner, upper, lower surface of palm. Carpus with blunt tooth at distal margin, sharp notch along articulation with chela, 2 teeth on lower margin along distal edge. Merus with large tooth at distal inner end, large tooth, row of teeth along lower edge, 2 teeth parallel, inner to this row. Ischium with tubercles in line with those of merus. Pereopods 2, 3 chelate, sparsely setose. Pereopods 4, 5 with dactyls forming claws. Ischia of all pereopods lacking hooks. Male pleopod 1 simple in structure, slender setose ridge along distal mesial surface. Male pleopod 2 with strong endopod, slender exopod. Female pleopod 1biramous. Abdomen heavy. Abdominal somites decreasing in size from 1–5, with pleura ending in points curving posteriorly. Pleura of abdominal somite 6 prolonged into hook around base of uropods. Telson with horizontal fissure along dorsal surface near posterior end, 2 lateral teeth in line with this fissure. Outer uropod with fissure across dorsal surface, 2 lateral teeth along fissure, median ridge. Inner uropod with median ridge. Total length to 117 mm.

Color in life. Dark brown to dark greenish. The color notes are from specimesn from Lake Tahoe , Nevada .

Habitat and depth. Rivers, streams, lakes, sloughs; less than 1 m to as much as 40 m (Lake Tahoe, Abrahamsson & Goldman 1970).

Range. British Columbia, Washington, Idaho, Oregon, Nevada (Lake Tahoe area) and California, south at least as far as Little Sur River, Monterey County. Introduced into Sweden. Type locality Columbia River, Oregon. Miller & Van Hyning (1970: fig. 3) provided a map of the range of the species in Oregon. Larson & Olden (2011: fig. 1) gave a map of the distribution of the subspecies in Oregon, Washington, southern British Columbia and extreme northwestern California.

Remarks. Three subspecies of P. leniusculus have been described: P. leniusculus leniusculus (Dana, 1852) ; P. leniusculus klamathensis (Stimpson, 1857) and P. leniusculus trowbridgii (Stimpson, 1857) . Hobbs (1976) noted that the descriptions do not clearly define these subspecies, and their ranges overlap. Due to human activity, the subspecies have been introduced into new areas and have intermingled.