Pacifastacus okanaganensis Larson, 2025

Pacifastacus okanaganensis Larson sp. nov.

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( Fig. 7 View FIGURE 7 , Table 3)

Astacus klamathensis. View in CoL — Lord, 1866: 278.

Astacus Klamathensis.— Hagen, 1870: 93 View in CoL , 94, 98, 102, pl. III fig. 169a, b, c [all in part].

C. Klamathensis View in CoL .— Hagen, 1870: 102 [erroneous combination].

A. klaymathensis .— Huxley, 1880: 223 [in part; erroneous spelling].

Astacus Klamathensis.— Faxon, 1884: 151 View in CoL [in part].

Astacus klamathensis. View in CoL — Faxon, 1885: 130, 131, 132 [all in part].

Astacus klamathensis. View in CoL — Faxon, 1890: 634 [in part].

Astacus klamathensis. View in CoL — Faxon, 1898: 665 [in part].

Potamobius (Potamobius) klamathensis (Stps.) .— Ortmann, 1902: 286 [in part].

Pacifastacus klamathensis View in CoL .—Bott, 1950: 24 [by implication, in part].— Miller, 1960: 130, 132, 197, 198, pl. VIII fig. 39 [all in part].

Pacifastacus leniusculus klamathensis View in CoL .— Miller, 1960: 133, 146, 160, 180, 181 [all in part].

Pacifastacus leniusculus View in CoL .— Hobbs, 1972: 21 [by implication].— Larson & Olden, 2011:64 [in part].

Pacifastacus leniusculus leniusculus View in CoL .— Hobbs, 1972: 21 [in part].— Hobbs, 1974: 6 [in part; neither fig. 5 nor 6, p. 81 = P. okanaganensis sp. nov.].

Pacifastacus leniusculus klamathensis View in CoL .— Hobbs, 1974: 22 [in part].— Larson et al., 2012: 3, 6, 12, fig. 1 [all in part].— Larson & Williams, 2015: 413, 419, 424 [in part], fig. 17.2.

Pacifastacus (Pacifastacus) leniusculus klamathensis View in CoL .— Bouchard, 1978: 431 [by implication; in part].— Hobbs, 1989: 82 [in part].

Pacifastacus (Pacifastacus) leniusculus leniusculus View in CoL .— Hobbs, 1989: 82 [in part].

Pacifastacus lenisculus lenisculus .— Fitzpatrick, 1983: 155 [erroneous spelling].

Pacifastacus leniusculus View in CoL .— Larson et al., 2012: 2, 3, 4, 5, 6 [all in part].

Pacifastacus klamathensis View in CoL .— Larson et al., 2012: 2, 3 [in part]

Okanagan group.— Larson et al., 2012: 7, 8, 10, 12 [by implication], 13, fig. 2, table 1, 2. — Larson & Williams, 2015: 419, 426, fig. 17.2.— Larson et al., 2016: 10, 12, fig. 3.

Pacifatacus leniusculus klamathensis View in CoL .— Larson & Williams, 2015: 413 [erroneous spelling].

Type material. Holotype ( RBCM 012-00121 View Materials - 003 View Materials ), male, Jewel Lake , British Columbia (49.1827°, -118.6000°) . Allotype (RBCM-012-00121-004), female, Jewel Lake , British Columbia (49.1827°, -118.6000°) .

Other material. RBCM 012-00100-001, Deep Lake, Washington (47.5878°, -119.3385°); RBCM 012-00121- 001, Jewel Lake, British Columbia (49.1827°, -118.6000°); RBCM 012-00122-011, Blueberry Creek, British Columbia (49.2593°, -117.9389°); RBCM 012-00123-001, Kettle River, British Columbia (49.1097°, -118.9792°); RBCM 012-00124-001, Idabel Lake, British Columbia (49.7404°, -119.1794°); RBCM 012-00125-001, Okanagan Lake, British Columbia (50.1802°, -119.4412°); RBCM 012-00304-001, Park Lake, Washington (47.5879°, - 119.3964°). Number of specimens by sex in Table 1.

Type locality. Jewel Lake, Jewel Lake Provincial Park, British Columbia (49.1827°, -118.6000°).

Diagnosis. Pacifastacus with rostrum bearing single pair of marginal tubercles or spines; acumen length less than 79.4% of anterior rostrum width; rostrum length more than 18.85% of TCL ( Fig. 3 View FIGURE 3 ).

Description. Body and eyes pigmented. Eyes not reduced. Rostrum deflected ventrally, base and anterior broad, margins sub-parallel, non-serrate; median carina subtle; acumen strongly converging, separated from remainder of rostrum by weak spines or tubercles; length 62% of anterior rostrum width (12%sd).Rostrum length including acumen 150% of base rostrum width (14% sd) and 21% of TCL (2% sd); anterior rostrum width 75% of posterior rostrum width (5% sd). Cephalothorax subcylindrical; postorbital ridge not terminating in spine, occasionally terminating in tubercle; TCL 203% of carapace width (9% sd); areola length 33% of TCL (1% sd), 233% of areola width (29% SD); areola width 29% of total carapace width (4% sd). Third pereopods without hook on ischium. Chelae without tubercles; palm length 87% of maximum chelae width at palm (12% sd); 36% of propodus length (10% sd); chelae height 63% of maximum chelae width at palm (3% sd). First pleopod (gonopod) of males nondescript, typical for genus. Annulus ventralis lacking, typical for genus.

Holotypic male. Body compressed dorsoventrally ( Fig. 7A View FIGURE 7 ). Rostrum broad, deflected ventrally; margins sub-parallel with anterior width 78% of posterior width, without spines or tubercles; median carina weak ( Fig. 7B View FIGURE 7 ). Rostrum length 110% of posterior width and 16% of TCL; acumen 34% of rostrum length. Carapace slightly wider (103%) than abdomen, maximum depth less (83%) than carapace width; TCL 27.4 mm; areola 227% longer than wide, 34% of TCL ( Fig. 7B View FIGURE 7 ); short postorbital ridges terminating in small tubercle, carapace otherwise lacking tubercles or spines. Abdomen slightly longer than carapace (108%). Palm length 90% of palm width, palm depth 62% of palm width (all measurements and counts based on right chela; Fig. 7C View FIGURE 7 ). Gonopod nondescript, typical for genus ( Fig. 7D, E View FIGURE 7 ). Epistome with semi-circular anterior lobe, lacking setae ( Fig. 7F View FIGURE 7 ). Right antennal scale 4.9 mm long and 1.7 mm wide ( Fig. 7H View FIGURE 7 ). Third pereopods without hook on ischium.

Allotypic female. Differing from holotype in following respects: TCL 21.7 mm; areola length 34% of TCL, 228% longer than wide; anterior rostrum width 77% of posterior rostrum width; rostrum length 132% of posterior width, 19% of TCL, acumen 32% of rostrum length; palm length 86% of palm width, palm depth 61% of palm width (all measurements and counts based on right chela). Antennal scale 3.7 mm long and 1.4 mm wide. Annulus ventralis absent ( Fig. 7G View FIGURE 7 ).

Size. The largest individual measured at RBCM was 47.0 mm TCL.

Color. Olive brown to brick red ( Fig. 8 View FIGURE 8 ). The white mark at the joint of the dactyl and propodus in P. leniusculus is generally absent or reduced.

Etymology. From an Okanagan-Salish language place name. We propose the common name of the “Okanagan Crayfish” due to the distribution of P. okanaganensis sp. nov. throughout the Okanagan and Thompson plateaus and Okanagan Lake, British Columbia, as well as Okanogan County, Washington, and due to the Okanagan lineage terminology of Larson et al. (2012) and Larson et al. (2016).

Geographic distribution and habitat. Pacifastacus okanaganensis sp. nov. has been most often collected from relatively isolated, mid-elevation lakes in the Okanagan and Thompson plateaus of British Columbia and Washington ( Fig. 6 View FIGURE 6 ). The species has also been collected from large Okanagan Lake in British Columbia , and lakes below Dry Falls in central Washington at Sun Lakes State Park (Deep and Park lakes). The only lotic records for the species are from the Kettle River and Blueberry Creek in British Columbia . Blueberry Creek was sampled as the outlet stream immediately below Nancy Greene Lake in Nancy Greene Provincial Park. Whether the species was more prevalent in the mainstem Columbia River before invasion of F. virilis is unknown ( Larson et al. 2010). Fish and Trout lakes in Washington , documented by mtDNA sequencing in Larson et al. (2012), are the only locations from past sequencing work not vouchered at RBCM ( Fig. 6 View FIGURE 6 ). The eastern range extent of the species into the upper Columbia River watershed of British Columbia, Idaho , and Montana is unknown. Pacifastacus okanaganensis sp. nov. has never been detected west of the Cascade Mountains in coastal British Columbia or Washington.

Life history notes. Life history of P. okanaganensis sp. nov. has not been studied, and berried or ovigerous individuals are not included among the RBCM vouchers. Pacifastacus okanaganensis sp. nov. life history might be anticipated to broadly resemble other congeners, as slower-growing and with lower fecundity proportional to carapace length relative to members of the family Cambaridae native to eastern North America ( Momot 1984).

Conservation status. Pacifastacus okanaganensis sp. nov. could be vulnerable to displacement by invasive F. virilis , common in the mainstem Columbia River of Washington ( Larson et al. 2010) and recently discovered in this watershed in British Columbia ( Phillips 2024). Pacifastacus leniusculus could also threaten P. okanaganensis sp. nov. with displacement, as it has impacted congeners in California ( Bouchard 1977; Light et al. 1995; U.S. Fish and Wildlife Service 1988). Pacifastacus okanaganensis sp. nov. is known from more locations than P. malheurensis sp. nov., and many of these locations are relatively isolated, mid-elevation lakes that may be difficult for other crayfish species to spread into without the assistance of human introductions. As the magnitude and timing of displacement of P. okanaganensis sp. nov. by either F. virilis or P. leniusculus in the Columbia River watershed is unknown, we recommend a global IUCN conservation status of data deficient ( IUCN 2012). We recommend rankings of Imperiled in both British Columbia and Washington because only four or five occurrences of P. okanaganensis sp. nov. are known from each of these jurisdictions ( Fig. 6 View FIGURE 6 ).

Crayfish associates. Pacifastacus okanaganensis sp. nov. was not collected in sympatry with other crayfish species by Larson et al. (2012) or Larson et al. (2016). Both F. virilis and P. leniusculus occur in the vicinity of P. okanaganensis sp. nov. populations, including in the mainstem Columbia River.

Relationships and comparisons. Pacifastacus okanaganensis sp. nov. is morphologically similar to P. malheurensis sp. nov. and P. l. klamathensis from coastal, southwestern Oregon and northwestern California. Pacifastacus okanaganensis sp. nov. generally has an acumen length less than 79.4% of anterior rostrum width, whereas P. leniusculus generally has an acumen length greater than 79.4% of anterior rostrum width ( Fig. 3 View FIGURE 3 ). Pacifastacus okanaganensis sp. nov. generally has a rostrum length greater than 18.85% of TCL, whereas P. malheurensis sp. nov. generally has a rostrum length less than 18.85% of TCL ( Fig. 3 View FIGURE 3 ). Pacifastacus l. leniusculus in particular are easy to differentiate from P. okanaganensis sp. nov. by the long, spiny rostrum and chelae with short, convex palms ( Hobbs 1972). Pacifastacus okanaganensis sp. nov. has not been collected in sympatry with P. malheurensis sp. nov. or coastally distributed P. l. klamathensis and may be also differentiated by geographic range.