Cambarus cracens R. W. Bouchard & Hobbs 1976

Cambarus (Exilicambarus) cracens

DIAGNOSIS.—Identical to diagnosis of subgenus.

HOLOTYPE MALE, FORM I.—Cephalothorax (Figure 1e, see also Figure 2a, j) subcylindrical in cross section. Abdomen narrower than thorax (18.4 and 19.9 mm). Greatest width of carapace greater than height at caudodorsal margin of cervical groove (17.6 and 14.8 mm). Areola 3.4 times as long as broad with 6 widely spaced punctations across narrowest part; length of areola 31.9 percent of entire length of carapace (41.9 percent of postorbital carapace length). Rostrum with slightly thickened, convergent margins bearing prominent acute corneous tubercles at base of acumen; latter almost reaching distal end of ultimate podomere of antennular peduncle and terminating in corneous, subspiculiform tip, acumen slightly upturned apically; dorsal surface of rostrum concave and bearing small setiferous punctations, latter more numerous in depression at level of caudal margin of orbit. Subrostral ridge weak and evident in dorsal aspect almost to base of marginal tubercle of rostrum. Postorbital ridge moderately strong with prominent knob at caudal extremity, grooved dorsolaterally, and with spiniform corneous tubercle cephalically. Suborbital angle broadly rounded, virtually nonexistent; branchiostegal spine moderately large, acute, and curved cephalodorsally. Cervical spine well developed and flanked by several small tubercles, at least one of which acute; hepatic area with scattered tubercles; cephaloventral part of branchiostegite with crowded tubercles and few adjacent and caudoventral to cervical spine, remaining lateral portion of branchiostegite granulate and dorsolateral portion finely, but densely, punctate.

Abdomen (Figure 1a) shorter than carapace (35.0 and 35.4 mm); pleura of moderate length, broad with caudoventral extremity of second through fifth rounded. Cephalic section of telson (Figure 1b) with 1 spine in caudodextral corner and 2 in caudosinistral, more mesial one movable. Proximal podomere of uropod with small distal spine on lateral lobe and larger one on mesial lobe; both rami with distinct median keel, that on mesial ramus with well-developed premarginal spine; lateral margin of lateral ramus subserrate with fixed and movable spines at extremity of proximal section; corresponding margin of mesial ramus with spine at distolateral angle.

Cephalic lobe of epistome (see Figure 2i of paratypic male, form I) apparently injured, rounded but with asymmetrical emargination cephalodextrally, margins only slightly thickened and marginal areas somewhat elevated, cephalomedian projection rather weak; main body of epistome with fovea represented by shallow depression not nearly so distinct as that illustrated, and arched epistomal zygoma flanked cephalolaterally by usual pair of slitlike fossae. Proximal segment of antennule with prominent spine on ventral surface at base of distal two-fifths. Antennal peduncle with lateral spine on basis and distal spine on ischium, flagellum extending caudally to third abdominal tergum. Antennal scale (see Figure 2g of paratypic male) rather broad, broadest distal to midlength, distomesial portion of lamellar area evenly rounded; distolateral spine strong, with long corneous tip, and reaching slightly beyond tip of rostrum. Postaxial surface of third maxilliped with stiff setae studding mesial half, row of submarginal shorter setae laterally, and with scattered setiferous punctations between submarginal row and clusters of stiff setae; distolateral extremity angular but not produced in spiniform projection.

Right chela (Figure 1f; see also Figure 2l) 3.7 times as long as broad (28.1 and 10.7 mm), subovate, slightly depressed; mesial margin of palm with irregular row of 8 tubercles, 2 immediately ventral to row and irregular row of 8 immediately dorsolaterally; remainder of palm studded with squamous tubercles, although few present ventromesially; distoventral surface of palm with usual prominent tubercle at base of dactyl and several somewhat larger than neighboring ones extending proximomesially from submedian ridge on fixed finger. Lateral surface of propodus costate with row of punctations causing irregular appearance of proximolateral margin on fixed finger and distolateral part of palm. Both fingers with well-defined submedian ridges flanked by setiferous punctations dorsally and ventrally; opposable surface of fixed finger with row of 5 rounded tubercles, fourth from base largest, along proximal two-fifths of fingers, and broad band of minute denticles (between, ventral to, and beyond tubercles) reaching base of corneous tip of finger; usual large, single, more ventral tubercle lacking. Opposable margin of dactyl with row of 5 tubercles along proximal three-fifths; proximal 3 tubercles subequal in size and much larger than distal 2, distalmost somewhat removed from more proximal 4, and additional large tubercle present more ventrally between distal 2 tubercles of row; minute denticles dispersed very similarly to those on fixed finger; lateral surface of dactyl tuberculate along proximal half and punctate distally.

Carpus longer than broad (10.3 and 6.9 mm) with moderately deep oblique furrow dorsally; mesial surface with prominent procurved spine near midlength and very small tubercle proximally (carpus of left chela with two procurved spines); distoventral margin with strong submedian spiniform tubercle, another on ventrolateral articular knob, and 2 smaller tubercles proximomesial to submedian one; podomere otherwise sparsely punctate.

Dorsal surface of merus with irregular row of small tubercles and 2 subdistal spines; mesial and lateral surfaces with scattered punctations; ventral surface with mesial row of 10 (8 on left cheliped), mostly spiniform, tubercles, and 2 (4 on left) strong ones representing lateral row; also spine present on ventral margin of distolateral articular knob. Ischium with row of 5 small tubercles ventromesially.

Hook on ischium of third pereiopod only (see Figure 2h of paratypic male, form I); hook simple, overreaching basioischial articulation and not opposed by tubercle on basis. Coxa of fourth pereiopod with moderately prominent caudomesial boss, that of fifth well developed but much less conspicuous than that on fourth. (See “Measurements.”)

First pleopods (Figure 1c,d; see also Figure 2b, f) reaching coxae of third pereiopods when abdomen flexed. See “Diagnosis” for description. (The almost straight distal half of the pleopod directed at about 135 degrees to the main shaft of the appendage is a unique feature of this crayfish.)

ALLOTYPIC FEMALE.—Excluding secondary sexual features, differing from holotype in following respects: epistome symmetrical, more nearly subtriangular and fovea slightly deeper; cephalic section of telson with 2 spines in each caudolateral corner; more lateral row of tubercles on dorsomesial surface of palm of chela consisting of 6 or 7 tubercles; ventral surface of palm with fewer and smaller tubercles, row extending proximomesially from submedian ridge on fixed finger in holotype not recognizable; opposable margin of fixed finger with row of 10 tubercles, that of dactyl with 9 on right and 11 on left chela; carpus of both chelipeds with 2 procurved tubercles mesially but lacking small tubercle on proximomesial surface; only 1 small tubercle proximomesial to median ventromarginal tubercle; merus with 3 subdistal acute tubercles dorsally on left cheliped, ventral surface with 10 tubercles in mesial row and 4 in lateral, right cheliped with 12 and 3 respectively; ischium with 4 tubercles on right and 3 on left cheliped. (See “Measurements.”)

Annulus ventralis (Figure 2k) distinctly asymmetrical and cephalic region not nearly so strongly calcified as caudal; cephalic half with shallow, submedian, longitudinal trough; sinus originating at sinistrocaudal end of latter and extending sinistrally, making hairpin turn, returning almost to median line before forming broad arc over caudal wall, there crossing median line and ending very slightly dextral to it; tongue directed sinistrally into fossa. Postannular sclerite 2.5 times as broad as long and half as wide as annulus. First pleopod almost reaching midlength of annulus when abdomen flexed.

MORPHOTYPIC MALE, FORM II.—Differing from holotype in following respects: epistome resembling that of allotype; tubercles flanking cervical spine on holotype and allotype not evident; cephalic section of telson with 2 spines in each caudolateral corner; opposable margin of fixed finger of right cheliped with 3 (4 on left) tubercles (third from base largest) along proximal third of finger, and large, more ventrally placed tubercle at base of distal two-fifths (absent on left); opposable margin of dactyl of right chela with 3 (5 on left) tubercles along proximal fourth and more ventrally placed one (absent on left) at end of proximal third; mesial surface of carpus of left cheliped with 2 procurved spines and smaller proximal tubercle; 3 subdistal spines dorsally on merus of right cheliped, ventral surface with mesial row of 9 and lateral one of 3 tubercles on both chelipeds; ischia of both with row of 3 tubercles; hook on ischium of third pereiopod much reduced, not overreaching basioischial articulation; bosses on coxae of fourth and fifth pereiopods also greatly reduced. (See “Measurements”.) First pleopods (Figure 2c,e) with mesial process lacking acute extension; central projection noncorneous, more massive, not so strongly recurved, with subacute apex directed caudally at approximately 90 degrees; only trace of caudal element evident.

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