Cambarus acuminatus Faxon, 1884

Williams, Bronwyn W., Delekta, Emmy M. & Loughman, Zachary J., 2019, Redescription and circumscription of the Acuminate Crayfish, Cambarus acuminatus Faxon, 1884 (Decapoda: Cambaridae), Zootaxa 4560 (1) : -

Cambarus acuminatus Faxon, 1884

Figures 1 , 2 A–K, 3, Table 1.

Diagnosis. Body and eyes pigmented. Rostrum lanceolate, weakly excavated, and ventrally deflected anteriorly, rostral margins pronounced and entire to acumen, and sub-parallel; converging to acumen. Acumen acuminate with prominent dorsally deflected spiniform tubercle at terminus. Areola 2.8–4.1 (x̄= 3.4, σ = 0.4, n = 15) times as long as wide with 3–5 (usually 3) punctations across narrowest point. Lateral portion of branchiostegal region of carapace heavily punctate; strong cervical spines present. Mandibular and orbital regions of carapace also punctate with well-developed tubercles. Prominent branchiostegal, basipodite, and ischiopodite spines present. Postorbital ridge terminating anteriorly in well-developed spine. Suborbital angle acute. TCL 1.8–2.1 (x̄= 1.9, σ = 0.1, n = 15) times greater than width. Postorbital angle absent.

Form I and II males possessing hook on ischium of third pereopod only; hook gently curved at apex, overarching basioischial joint in form I males, not reaching basioischial joint in form II males; hook not opposed by tubercle on third pereopod boss.

Mesial surface of palm of chela possessing two rows of tubercles; first row consisting of 5–8 tubercles; second row 4–6. Single well-pronounced subpalmar tubercle present. Dorsomedian ridge of fixed finger of propodus pronounced. Lateral impression at base of fixed finger. Chelae palm punctate. Dactyl possessing strong dorsal longitudinal ridges with pronounced tubercles. Both dactyl and propodus possessing enlarged tooth or denticle at midlength in opposition to each other. Dactyl and fixed finger each with sharp corneous subterminal tip. Ventrolateral margin of merus with three enlarged spines; ventralmesial margin with 6–10 smaller spines. Well developed enlarged carpal spine present surrounded by additional smaller spines.

Gonopod of form I male with long terminal elements. Central projection sickle shaped and not tapering distally; recurved> 90° to main shaft of gonopod, possessing subapical notch. Gonopod lacking caudal knob. Mesial process directed approximately 90° to shaft, bent cephalolaterally; inflated proximally with distinct hump; tapering to a blunt terminus distinctly caudal to slightly cephalic of terminance of central projection, and; not projecting beyond gonopods umbo. Annulus ventralis immovable; distinctly asymmetrical caudally; cephalic portion with median trough leading to strongly sculptured central fossa; exaggerated “S” bend in sinus terminating at caudal edge.

Size. Form I male (n = 16) TCL ranges in size from 13.3–21.0 mm (PCL 11.7–16.8 mm) with a mean TCL of 16.9 mm. Mean TCL of form II male (n = 5) is 13.6 mm, ranging in size from 11.5–16.7 mm (PCL 10.0–12.0 mm). Female (n = 6) mean TCL is 16.2 mm and ranges from 14.2–20.1 mm (PCL 12.3–17.1 mm). The largest specimen examined was a form I male with a TCL of 21.0 mm (PCL 16.0 mm).

Male, form I (NCSM 21000; Figs. 2 A–C, E–F, I–J, Table 1). Body ( Fig. 2A, B ) Slightly compressed dorsoventrally; thoracic section of carapace slightly wider than abdomen and cephalic section of carapace. Carapace height less than carapace width (16.3 and 18.1 mm, respectively). TCL 34.3 mm; PCL 28.0 mm. Areola 3.5 times longer than wide, with 4 punctations across narrowest part; length of areola 33.5% of TCL (41.1% of PCL). Rostrum narrow and lanceolate with acuminate acumen and weakly excavated equally along length; margins slightly thickened and converging caudal to acumen; floor of rostrum with numerous punctations. Rostrum 1.7 times longer than wide. Rostrum distinctly lanceolate, ending in dorsally turned corneous tip ( Fig. 2A ). Postorbital ridges moderate in length, terminating in spinose dorsally deflected tubercles. Suborbital angle inconspicuous, i.e., absent sensu Hobbs (1981) ( Fig. 2A ). Prominent, large cervical spine present; mandibular, branchiostegal, and orbital regions of carapace heavily tuberculated; greatest tubercle density in hepatic region. Tubercles in the hepatic region prominent and well developed. Prominent, large branchiostegal spine present, and antennal ischiopodite and antennal basiopodite spines present ( Fig. 2B ).

Abdomen slightly shorter than carapace, pleura sharply rounded cephaloventrally, angled caudoventrally. Cephalic section of telson with 2 large spines in each caudolateral corner ( Fig. 2I ). Proximal podomere of uropod with 2 distolateral spines on mesial lobe; median spine, originating from ventral surface; mesial ramus of uropod with median ridge ending distally in distomedian spine not overreaching margin of ramus. Distal margin of proximal segment of lateral ramus of right uropod bearing 13 immovable, small spines. Cephalomedian lobe of epistome sub-hexagonal, forming weak angle at junction with endostyle; cephalolateral margins not thickened ( Fig. 2C ); main body possessing weak cephalomedian fovea. Antennal scale broadest distally; lateral margin thickened, terminating in very large corneous spine; setiferous mesial margin. Right antennal scale 5.9 mm long, 2.3 mm wide. Tip of right antenna reaching middle of telson when adpressed. Missing left antennae. Mesial surface of palm of right chela with 2 well-defined tubercle rows; 7 tubercles in first row, 6 in second row ( Fig. 2J ). Palm length 60.4% of palm width; depth of palm 7.6 mm. Ventral surface of palm lacking tubercles. Dorsal longitudinal ridge of dactyl well developed and possessing 9 prominent disorganized tubercles ( Fig. 2J ); dactyl terminating in large sharp corneous tip. Dorsomedian ridge of fixed finger of propodus strongly developed with prominent lateral impression at junction of fixed finger and palm. Two large tubercles on propodus and single large tubercle on the dactyl at mid length of both structures. Fixed finger of propodus with sharp corneous subterminal tip. Carpus with prominent dorsal furrow ( Fig. 2J ), surface covered with setiferous punctations; mesial margin with large, procurved large spine at about mid-length. Distodorsal surface of merus with single, large spine and tubercle; 3 large spines on ventrolateral surface of merus. All measurements and counts from right chela. Hook on ischium of third pereopod only; gently curved at apex, overarching basioischial joint, not opposed by tubercle on base. Form I gonopod with subapical notch; central projection length not reaching distal portion of mesial process (Figs. E, F).

Adult female (NCSM 21001; Figs. 2D, K ). Differing from form I male in following respects: carapace height less than carapace width (19.0 and 21.8 mm, respectively); TCL 39.0 mm, PCL 32.8 mm. Areola length 36.9% of TCL (43.9% of PCL), 3.8 times as long as wide. Mesial margin of palm of chela with two rows of tubercles; mesial-most row with 5 tubercles, second row with 5 tubercles. Palm length (9.9 mm) 71.7% of palm width (13.8 mm). All measurements and counts from right chela. Antennal scale ( Fig. 2K ) 8.1 mm long, 3.7 mm wide. Annulus ventralis as described in diagnosis ( Fig. 2D ); width of postannular sclerite half total width of annulus ventralis; first pleopods uniramous, reaching central region of annulus ventralis when abdomen flexed.

Male, form II ( Figs. 2 G–H). Differing from form I male in the following respects: carapace height greater than carapace width (14.4 and 16.5 mm respectively); TCL 31.0 mm and PCL 26.3 mm. Areola length 35.5% of TCL (42.8% of PCL), 3.8 times longer than wide. Rostrum margins acuminate and entire; rostrum ventrally deflected and excavated; rostrum 1.9 times as long as wide. Abdomen 34.7 mm long. Mesial margin of palm of chela with two rows of tubercles; mesial-most row with 6 tubercles; second row with 5 tubercles. Palm length (7.2 mm) 65.5% of palm width (11.0 mm). All measurements and counts from right chela. Antennal scale 5.9 mm long, 2.4 mm wide. Gonopods reaching anterior margin of 4 th pereopod caudomesial boss. Central projection curved 90° to shaft ( Fig. 2 G–H). Mesial process tapered, bulbous, directed caudolaterally. Hook on ischium of third pereopod small, not reaching basioischial joint.

Color. Carapace ground color of C. acuminatus light red-brown to orange-brown ( Fig. 3 ); posterior margin of carapace red-brown to red, without saddle. Hepatic and antennal region of carapace with beige punctations. Postorbital ridge red-brown ending in pronounced tan spine. Rostrum margins and acumen cream to orange, orange-brown, olivaceous or tan. Cephalic section of carapace immediately anterior of cervical groove light redbrown; cervical groove black dorsally; mandibular abductor scars mottled, ranging from light-brown, brown, to red-brown. Lateral margin of antennal scale red-brown to brown; body of antennal scale brown. Antennal flagellum and antennules green-brown, with olivaceous hue; dorsal surface of lamellae tan to brown; ventral surface light-green to olivaceous. Dorsal surface of chelae generally olivaceous or green-brown, with beige punctations. Denticles on opposable surfaces of fingers yellow, white, or tan. Ventral surface of chelae cream or tan. Dorsal surface of carpus olivaceous or green-brown; region adjacent to and including furrow olive-brown to olive; carpus spine yellow. Merus olive-brown or olive. Podomeres of pereopods olivaceous, light brown, or greenbrown; joints of pereopod podomeres pink or beige. Dorsal and dorsolateral surface of abdomen same colors as carapace; tergal margins crimson red; abdomen lacking dorsal stripe. Uropods same colors as abdomen. Ventral surface of abdomen and carapace cream. Dorsal ridge of form I gonopod central projection amber; body of central projection, gonopod, and mesial process tan. Form II gonopod and all associated processes cream. Cephalic portion of annulus ventralis pink to pink-cream; ridge of fossa pink; caudal region of annulus ventralis ranges from pink to cream colored.

Habitat. Specimens, deemed representative of C. acuminatus , from the South Saluda River (Saluda River drainage) adjacent to US 276/Hwy. 11, 7.1 km (4.4 mi) west of Cleveland, Pickens County, South Carolina (N 35.0737, W 82.5897), were collected June 2018 by E.M. Delekta, Z.L. Loughman, and B.W. Williams. The South Saluda River at this locality ranges from 4 to 8 meters wide, and 0.25 to 1.5 meters deep. The streambed consists of sand, cobbles and gravels, with several large sandstone slabs present throughout the samples reach. Riffles, runs, and pools are present, and Podostemum ceratophyllum occurs on boulders in faster velocity flows. Cambarus acuminatus individuals were taken primarily from under slab rocks mid channel in riffles or slab rocks positioned in eddies along the streams banks. One animal was retrieved from under a boulder that was partially embedded in loose sandy substrates.

Cambarus acuminatus is most frequently found in third, or higher, order streams with moderate to high gradients throughout the upper Saluda River drainage, in the Appalachian foothills at or above the fall line. Substrates with cobbles, slab boulders to boulder clusters in runs and riffles appear to be frequent haunts of adults. Juveniles and neonates were often taken from leaf packs in pool thalwegs, root wads, undercut banks and coarse woody debris snags. Based on our surveys, C. acuminatus numbers rapidly decline as habitat, in part influenced by decreasing stream gradient, transitions into the Piedmont proper.

Distribution and specimens examined. The distribution of C. acuminatus sensu lato, based on records of the species—as “ Cambarus acuminatus ”—retrieved from USNM, NCSM, and WLU Collections, extends from central South Carolina north through much of North Carolina and Virginia, and into Maryland and Pennsylvania ( Fig. 1 ). As a whole, this sprawling distribution exemplifies what is known as the C. sp. C complex. Although several taxa have been split from the core of this complex (e.g., Cambarus hobbsorum Cooper, 2001 , Cambarus hystricosus Cooper & Cooper, 2003 , Cambarus johni Cooper, 2006 , Cambarus aldermanorum Cooper & Price, 2010 ), nearly all are known to co-occur with other, undiagnosed, morphotypes nested within C. sp. C. The nominal form of C. acuminatus , which we establish herein, appears to be restricted to the Saluda River drainage in northwestern South Carolina ( Fig. 1 ; Hobbs 1969; Z.J. Loughman & B.W. Williams unpubl. survey results).

We examined a total of 18 specimens from the following six collections from the South Saluda River drainage in Greenville and Pickens Counties, South Carolina. (1.) South Saluda River, 0.1 miles from the junction of Route 11 & US 276 adjacent to Route 11 at Pickens County line, N 35.07519 W 82.5724, USNM 144162, 12 June 1972, 1 IM, 2F. (2.) South Saluda River at SR 11 in NE limit of Pickens County, N 35.07519 W 82.5724, USNM 178028, 15 April 1982, 1 IM, 2 F, H.H. Hobbs Jr. and T.A. English. (3.) South Saluda River at SR 11 & US 276, 0.5 mi west of S-176, NW of Travelers, N 35.0737 W 82.5832, USNM 208331, 7 May 1983, 2 F, P.H. Carlson. (4.) South Saluda River/Mathews Creek confluence adjacent to SR 90, Greenville County, N 35.06293 W 82.64940, USNM 220075, 19 December 1967, 1 F, R. Prins. (5.) South Saluda River adjacent to US 276/Hwy 11, 7.1 km (4.4 mi) west of Cleveland, Pickens County, N 35.0737 W 82.5897, NCSM 21003 1 IIM, 3 F, NCSM 21000, NCSM 21001 (1 F), NCSM 21002 (1 IIM) (6.) South Saluda River at Ridge Springs Rd., NCSM uncat., N 35.063449 W 82.65041522, November 2018, 1 IM, 1 F, B.W. Williams and P.G. Weaver.

Crayfish associates. Other crayfish species collected in the Saluda River system in conjunction with C. acuminatus include Cambarus asperimanus Faxon, 1914 , Cambarus bartonii ( Fabricius, 1798) , Cambarus howardi , Cambarus robustus Girard, 1852 , Procambarus spiculifer and Procambarus clarkii , the latter of which is introduced in the Saluda River Basin.

Conservation status. Cambarus acuminatus appears to be stable at this time in upper reaches of the Saluda River system, although substantial threats do exist. The damming of the Saluda River in 1905, creating Saluda Lake, eliminated several kilometers of stream previously occupied by the species. The authors recently completed crayfish surveys throughout the Santee Basin of North and South Carolina, and discovered P. clarkii populations in the Saluda River system. This species—introduced into numerous waterways throughout South Carolina—is a notorious invader of freshwater ecosystems worldwide, with deleterious, and often devastating impacts on native ecosystems (Hobbs et al. 1989; Gamradt et al. 1997; Rodríguez et al. 2005; Souty-Grosset et al. 2016), including displacement of native crayfishes (e.g., Hanshew & Garcia 2012; Pearl et al. 2013). Spread of P. clarkii within the Saluda River drainage poses a serious threat to long term existence of the Saluda River endemic C. acuminatus . Urban and suburban development of and around Greeneville, South Carolina represent another potential threat to the continuity and health of streams in the Saluda River system, and in turn C. acuminatus . At present, populations in the South and North Fork of the Saluda River appear to be the most robust, and are protected, in part, within the Enoree District of the Sumter National Forest.

Figures

FIGURE 1. Map showing the distribution of Cambarus acuminatus sensu lato based on records in the North Carolina Museum of Natural Sciences (NCSM) Non-molluscan Invertebrate Collection (green circles), the West Liberty University (WLU) Crayfish Collection (yellow circles), and the Smithsonian Institution’s National Museum of Natural History (USNM) Invertebrate Zoology Collection (orange circles). Sub-basins (HUC-8 level) with solid shading denote the distribution of the C. species C complex; the dashed sub-basin denotes the Saluda River drainage, to which C. acuminatus sensu stricto is restricted.

FIGURE 2. Cambarus acuminatus (A) lateral view of carapace; (B) dorsal view of carapace; (C) epistome; (D) annulus ventralis; (E) lateral and (F) mesial view of form I gonopod; (G) lateral and (H) mesial view of form II gonopod; (I) telson and uropods; (J) dorsal view of right carpus and chelae, and; (K) dorsal view of right antennal scale. A–C, E–F, and I–J from form I male (NCSM 21000); D and K from adult female (NCSM 21001); G–H from form II male (NCSM 21002).

FIGURE 3. Cambarus acuminatus form I male, South Saluda River, Pickens County, South Carolina. Several branchiobdellidans (crayfish worms) can be seen on the crayfish, including the carapace, chelipeds, and uropods, under the rostrum, and behind the eye.