KEY TO THE SPECIES OF THE GENUS PACIFASTACUS
(Applicable to BOTH Sexes)
1.
Rostrum with single pair of marginal tubercles or spines (Fig., 12a-c):.......................................
.........................................................................................................Pacifastacus
leniusculus........
2
(The subspecies of P. leniusculus that have been described are not clearly
defined, and
their ranges
overlap - at least in part due to introductions -- to such an extent that it is
questionable that
they should be recognized. Only the most "extreme"
representatives
of the three can be
identified here).
- Rostrum with at least 3 pairs of marginal spines (Figs.
12d, 13).................................................... 4
 |
| Fig. 12. Dorsal view of carapacees. a) Pacifastacus l. leniusculus; b) P. l. trowbridgii; c) P. l. klamathensis; d) P. connectens. |
2(1).
Postorbital ridges almost always spiniform cephalically and with pair of spines
at posterior
bases; length of
acumen almost always greater than width of rostrum at level of marginal
spines (Fig.
12a;
see also Fig. 14e):.......Pacifastacus leniusculus
leniusculus (Dana, 1852).
(Streams and lakes in British Columbia, California, Idaho, Nevada, Oregon,
and
Washington. Literature: Faxon, 1885; Riegel).
- Postorbital ridges rounded or tuberculiform
cephalically and with or without low tuberculiform
prominences at posterior bases; length of acumen seldom equal to width of rostrum at level
of marginal spines, never in P. l. trowbridgii (Fig. 12b,c): ............................................................. 3
3(2).
Base of postorbital ridges with tubercles (Fig. 12b; see also
Fig. 5a):.........................................
................................................................Pacifastacus
leniusculus trowbridgii (Stimpson, 1857)
(Streams and lakes in British Columbia, California, Idaho, Nevada, Oregon, and
Washington.
Literature: Faxon, 1885; Hagen, 1870; Riegel, 1959).
- Base of
postorbital ridges without tubercles (Fig. 12c):
................................................................
................................................................Pacifastacus leniusculus klamathensis (Stimpson, 1857)
(Streams and lakes in British Columbia, California, Idaho, Oregon, and
Washington.
Literature: Faxon, 1885; Riegel, 1959).
4(1). Dorsal surface of palm of chela with two conspicuous clusters of setae (Fig. 14a,b): ............. 5
- Dorsal surface of palm of chela without two conspicuous clusters of setae (Fig. 14c,d): ........ 6
5(4).
Post orbital ridges with 1 or 2 pairs of posterior spines or tubercles;
rostrum lacking
median carina (Fig.
12d); dorsal surface of chela with comparatively prominent
tubercles (Fig.
14a):............................................................Pacifastacus
connectens (Faxon, 1914).
(Streams in Idaho and Oregon. Literature: Faxon, 1914).
- Postorbital ridges lacking posterior spines or
tubercles; rostrum often with median
carina (Fig. 13a); dorsal surface of chela with minute tubercles (Fig. 14b):................................
...................................................................................................Pacifastacus gambelii (Girard, 1852).
(Streams
and lakes on the Pacific Slope and in the Missouri River drainage in
California
(?), Idaho, Montana, Nevada, Oregon, Utah, Washington, and Wyoming.
Literature:
Hagen, 1870; Riegel, 1959).
 |
| Fig. 14. Dorsal view of chelae. a) Pacifastacus connectens; b) P. gambelii; c) P. fortis; d) P. nigrescens; e) P. l. leniusculus. |
6(4).
Width of palm of chela equal to, or greater than, length of mesial margin (Fig.
14c;
see
also Fig. 13c):
......................................................................Pacifastacus
fortis (Faxon, 1914).
(Streams in Shasta County, California. Literature: Faxon, 1914, Riegel, 1959).
- Width of palm of chela less than length of mesial
margin (Fig. 14d; see also Fig. 13b):............,
.........................................................................................Pacifastacus nigrescens (Stimpson, 1857).
(Streams in the vicinity of San Francisco, California. Literature:
Faxon, 1914;
Hagen,
1870; Riegel, 1959).
END OF PACIFASTACUS
Last Updated: 08 November 2005
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