Orconectes chickasawae

Orconectes chickasawae

Orconectes mississippiensis.—Hobbs, 1972:80, fig. 63a.

DIAGNOSIS.—Body and eyes with pigment. Rostrum without median carina, with or without marginal tubercles or small spines. Areola 16 to 100 times as long as wide and comprising 27.9 to 32.8 percent of entire length of carapace (37.1 to 42.6 percent of postorbital carapace length), with only 1 punctation in narrowest part. Cervical spine small; suborbital angle vestigial to obsolete; postorbital ridge well developed with small acute spine or tubercle cephalically. Antennal scale approximately 2.3 times as long as wide, broadest at about midlength. Chela depressed, tubercles on mesial margin of palm forming subserrate row; fingers gaping, and mesial margin of dactyl with subserrate row of often acute tubercles extending along almost entire length of finger; opposable margin of dactyl with distinct excision. Hook on ischium of third pereiopod of male. First pleopod of first form male without angular shoulder on cephalic surface, with rami curved throughout their length, and central projection reaching caudal part of coxa of second pereiopod when abdomen flexed; pleopod length divisible into carapace length 3.0 to 3.7 (average 3.3) times; terminal elements slender, subparallel; central projection constituting 20.8 to 26.4 (average 21.9) percent of mesial length of pleopod, bladelike, tapering to caudally directed apex, and not extending so far caudally as mesial process, latter subcylindrical in section proximally, troughlike distally. Annulus ventralis as figured. First pleopod present in female.

HOLOTYPIC MALE, FORM I.—Body and eyes pigmented. Cephalothorax (Figure 10a,i) subcylindrical in section; abdomen narrower than carapace (15.4 and 18.1 mm), width of latter greater than depth at caudodorsal margin of cervical groove (18.1 and 17.2 mm). Areola narrow, 30 times as long as wide, with 1 punctation in narrowest part; length of areola 33.2 percent of entire length of carapace (41.2 percent of postorbital carapace length). Rostrum with only slightly thickened, elevated borders, lacking marginal spines or tubercles, converging to base of short acumen, latter reaching distal end of penultimate podomere of antennular peduncle; upper surface subplane with thickly set, setiferous punctations. Subrostral ridge weakly developed and evident in dorsal aspect only at base of rostrum. Postorbital ridge moderately strong, grooved laterally, and terminating cephalically in small tubercle. Suborbital angle vestigial, broadly rounded. Cervical spine small. Branchiostegal spine well developed. Carapace densely punctate dorsally, finely granulate laterally except for longitudinal row of moderately large tubercles immediately ventral to cephalic portion of cervical groove. Abdomen and carapace subequal in length (36.5 and 36.1 mm); pleura well developed and subtruncate ventrally; cephalic section of telson with 2 spines in each caudolateral corner. Proximal podomere of uropod with short, corneous spine on each lobe, mesial ramus with moderately well-developed dorsomedian keel terminating in small premarginal spine.

Cephalic lobe of epistome (Figure 10g) lacking cephalomedian projection, and delimited basally by distinctly contracted base; margins crenulated, slightly elevated ventrally; main body with shallow fovea; epistomal zygoma broadly arched. Basal segment of antennule with spine on ventral surface slightly distal to midlength. Antennal peduncle devoid of spines except laterally on basis. Antenna reaching slightly beyond caudal margin of telson. Antennal scale (Figure 10l) 2.2 times as long as broad, with greatest width near midlength; mesial border of lamella evenly rounded; apical spine weak and reaching ultimate podomere of antennular peduncle. Ventral surface of ischium of third maxilliped with submarginal lateral row of long, plumose setae and with scattered shorter plumose ones on surface between lateral row and broad mesial band of stiff hairlike setae.

Right chela (Figure 10j) depressed, costate laterally, longer than carapace (43.5 and 36.1 mm) and 2.6 times as long as wide. Mesial surface of palm with 3 rows of tubercles: 8 in mesialmost and 10 (9 on left chela) and 6 in flanking dorsal and ventral rows, respectively. Mesial half of dorsal surface of palm tuberculate, tubercles progressively more squamous laterally; remaining surfaces of palm punctate; ventral surface with 2 large marginal tubercles at base of dactyl and 3 smaller ones situated more proximally. Fingers gaping basally. Opposable margin of fixed finger with dorsal row of 18 knoblike tubercles (fourth from base largest) decreasing in size distally, and almost reaching corneous tip of finger; ventral row of 6 tubercles along distal third of finger, proximalmost largest and large gap between it and second tubercle of row; finger devoid of minute denticles; dorsal surface with broad submedian ridge and narrower mesial one flanking base of dorsal row of tubercles on opposable margin, ridges flanked by setiferous punctations; lateral margin of finger costate, costa extending proximally to midlength of palm; ventral surface with submedian longitudinal ridge, otherwise punctate. Opposable margin of dactyl with conspicuous excavation in basal portion, bearing row of 23 knoblike tubercles (fifth from base largest and marking distal end of excavation) extending from base almost to corneous tip, tubercles decreasing in size distally from fifth; in addition 2 smaller tubercles on lower level at base of distal fourth, and minute denticles present between and distal to tubercles along distal three-fifths of finger; dorsal and ventral surfaces similar to those of fixed finger; mesial surface with cluster of subacute tubercles proximally, cluster narrowing distally to single row, surface in silhouette appearing serrate. Carpus about 1.4 times as long as broad, with sinuous groove dorsally, flanked mesially by tubercles and laterally by setiferous punctations; mesial surface with 3 prominent tubercles, distal 2 spikelike and distalmost largest; ventral surface with 2 large rounded tubercles on distal margin, 1 on lateral condyle and other submedian; ventromesial surface with cluster of 4 smaller tubercles opposite level of spikelike tubercles on mesial surface. Dorsal surface of merus with 5 subdistal tubercles (4 on left chela); lateral and mesial surfaces punctate; ventral surface with lateral row of 7 tubercles and mesial one of 14 (left chela with 7 laterally and 12 mesially) flanked by few additional tubercles; distolateral apophysis with small subacute tubercle. Ventromesial margin of ischium of cheliped with single tubercle. Ischium of third pereiopod (Figure 10h) with simple hook overreaching basioischial articulation and opposed by small tubercle on basis; hook massive, with free end truncate and subspatulate. Ventral membrane on coxa of fifth pereiopod studded with short setae.

First pleopods (Figure 10b,f,k) symmetrical and reaching caudal portion of second pereiopods when abdomen flexed. (See “Diagnosis” for description.)

ALLOTYPIC FEMALE.—Differing from holotype in following respects: abdomen and carapace subequal in width; areola only 23 times as long as wide, comprising 31.3 percent of carapace length (41 percent of postorbital carapace length); minute marginal tubercles at base of acumen; left postorbital ridge ending bluntly; abdomen longer than carapace (39.5 and 36.8 mm); cephalic lobe of epistome with margin less crenulate and with moderate cephalomedian projection; right chela shorter than carapace (28.9 and 36.8 mm); mesialmost row of tubercles on mesial margin of palm of chela consisting of 7, and flanking dorsal and ventral rows of 6 and 4, respectively; left chela probably regenerated; opposable margin of fixed finger with single row of 13 tubercles, 1 large one at base of distal three-fifths on lower level, single row of minute denticles between and distal to sixth tubercle from base, and proximomesial angle of finger with conspicuous tuft of plumose setae; opposable margin of dactyl with row of 17 tubercles; ventrodistal margin of carpus of cheliped with 1 additional tubercle. (See Table 5.)

Annulus ventralis (Figure 10d) moderately deeply embedded in and firmly fused to sternum, subpentagonal in outline, and about 1.5 times as broad as long. Cephalic half with median trough curving dextrally across midlength; sinus originating just cephalic to midlength in median trough, extending caudodextrally along and around long, digitiform tongue, following latter sinistrally—crossing median line—and, curving caudodextrally, ending before reaching caudal margin of annulus. Postannular plate about 3 times as broad as long, only little narrower than annulus. First pleopod extending well over (ventrally) annulus when abdomen flexed.

MORPHOTYPIC MALE, FORM II.—Differing from holotype in following respects: areola 37 times as long as wide, comprising 31.6 percent of carapace length (41.2 percent of postorbital carapace length); rostrum with marginal tubercles; cephalic portion of epistome slightly more rounded cephalically and with small cephalomedian projection; ischium of antennal peduncle with ventral spine; right chela shorter than carapace; mesial surface of palm with 7 tubercles in mesialmost row and 6 and 4 in flanking dorsal and ventral rows, respectively; ventral surface with group of 3 more proximal tubercles rudimentary; fixed finger with single row of 11 tubercles (fourth from base largest), single large tubercle ventral to row (situated between eighth and ninth tubercles of row), very small tubercle between tenth and eleventh, and minute denticles extending distally from fifth tubercle; proximomesial angle of finger with conspicuous tuft of plumose setae; dactyl with row of only 16 tubercles on opposable margin; mesial surface of right carpus with 4 prominent tubercles and additional prominent one immediately proximal to distal articular knob; ventral surface with 2 submarginal distal acute tubercles and 2 smaller rounded ones; dorsal surface of merus with 2 acute tubercles; ventral surface with lateral row of 4, and mesial row of 13 tubercles; ischium of third pereiopod with reduced hook not overreaching basioischial articulation. (See Table 5.)

First pleopod (Figure 10c,e) with terminal elements conspicuously heavier, more rounded, and distinctly shorter than those of holotype—shorter by virtue of much shallower cleft between two elements.

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Orconectes chickasawae eller «Chickasaw crayfish» er en art av ferskvannskreps innenfor slekten Orconectes (familie Cambaridae, orden Reptantia) som inngår i den store gruppen av såkalte tifotkreps. Dette er ferskvannskreps som på engelsk oftest kalles «crayfish».

Orconectes chickasawae er en av de om lag 85 artene i slekten, og har en utbredelse med forekomster i elver og innsjøer nesten utelukkende i delstaten Mississippi.