Orconectes holti

Orconectes holti

DIAGNOSIS.—Body and eyes with pigment. Rostrum without median carina, acumen distinctly delimited basally by marginal spines. Areola obliterated along part of its length and comprising 26.0 to 29.9 percent of total length of carapace (37.2 to 40.5 percent of postorbital carapace length). Cervical spine well developed; suborbital angle obtuse; postorbital ridge moderately strong with acute spine cephalically. Antennal scale 2.5 to 2.8 times as long as wide, broadest at or proximal to midlength. Chela depressed, lateral margin costate, tubercles on mesial margin forming subserrate row; fingers gaping and mesial margin of dactyl with subserrate (in silhouette) row of tubercles along at least basal two-thirds; opposable margin of dactyl with rather distinct excision in proximal third. Hook on ischium of third pereiopod in male. First pleopod of first form male without angular shoulder on cephalic surface, with rami curved throughout their length and reaching caudal part of coxa of second pereiopod when abdomen flexed; pleopod length divisible into carapace length 3.6 times (in only first form male available); terminal elements slender and subparallel; central projection constituting about 23 percent of entire length of pleopod, bladelike, and tapering from base to caudodistally directed apex; mesial process subcylindrical in section proximally, troughlike distally, its caudally directed tip extending caudally beyond end of central projection. Annulus ventralis as figured. First pleopod present in female.

HOLOTYPIC MALE, FORM I.—Body and eyes pigmented. Cephalothorax (Figure 8a,i) subcylindrical in section; abdomen narrower than carapace (12.8 and 15.2 mm), width of latter greater than depth at caudodorsal margin of cervical groove (15.2 and 13.5 mm). Areola obliterated for some distance along cephalic half, its length constituting 28.2 percent of entire length of carapace (39.3 percent of postorbital carapace length). Rostrum with slender, elevated margins converging from base to marginal spines delimiting acumen, latter reaching distal end of ultimate podomere of antennular peduncle and slightly depressed; upper surface distinctly depressed with numerous weakly setiferous punctations. Subrostral ridge weak and evident in dorsal aspect only at base of rostrum. Postorbital ridge moderately strong, grooved dorsolaterally, and terminating cephalically in strong spine. Suborbital angle moderately prominent but obtuse. Cervical and branchiostegal spines well developed. Carapace punctate, slightly granulate only in ventral part of cephalolateral area. Abdomen longer than carapace (36.2 and 33.3 mm); pleura well developed, subtruncate ventrally, and subangular caudoventrally; cephalic section of telson with 2 spines in each caudolateral corner. Proximal podomere of uropod with spine on each lobe, that on lateral very small; both rami with medial keel ending in spine, that on mesial ramus premarginal.

Cephalic lobe of epistome (Figure 8g) with cephalomedian projection, and delimited basally by distinctly contracted base; margins irregular, slightly elevated (ventrally) ventral surface with scattered setae, main body of epistome with broad cephalomedian depression bearing longitudinal trough; epistomal zygoma broadly V-shaped. Basal podomere of antennule with prominent spine on ventral surface slightly distal to midlength. Antennal peduncle with moderately strong spine on lateral surface of basis and another on ventral surface of ischium. Antenna reaching slightly beyond base of telson. Antennal scale (Figure 8l) 2.7 times as long as wide with greatest width proximal to midlength; mesial border of lamella subangular near distal extremity; apical spine reaching slightly beyond distal end of antennular peduncle. Ventral surface of ischium chium of third maxilliped with submarginal lateral row of long, plumose setae, lateral half of surface with scattered ones, mesial half studded with stiff hairlike setae; distolateral extremity of ischium with distinct corneous spine.

Right chela (Figure 8j) strongly depressed (ratio of depth to width 0.61), not so long as carapace (27.9 and 33.3 mm) and 3.3 times as long as wide; thickness equivalent to about two-thirds length of areola, and little more than four-fifths length of mesial margin of palm; latter with 8 (9 on left) tubercles, in mesialmost row subtended dorsally and ventrally by rows of 8 and 2 (left with 4), respectively; additional tubercles present on mesial third of dorsal surface, tubercles progressively more squamous laterally; remaining surfaces of palm punctate; ventral margin adjacent to opposable base of dactyl with row of 4 tubercles (ventralmost largest, others very small), and additional premarginal prominent one situated proximolateral to row. Fingers gaping, with inconspicuous small tuft of plumose setae extending distally from basal part of fixed finger. Opposable margin of latter with row of 17 knoblike tubercles (fifth from base largest) extending from base almost to corneous tip of finger (left with 13); except for small size of eighth from base, tubercles decreasing in size distally from fifth; large tubercle present more ventrally between thirteenth and fourteenth, and smaller one between fifteenth and sixteenth; single interrupted row of minute denticles extending distally from sixth tubercle from base; dorsal surface of finger with prominent submedian ridge and lesser one immediately lateral to row of tubercles on opposable surface, ridges flanked by row of setiferous punctations; lateral costa extending proximally along distal third of palm and basal half of finger; ventral surface punctate and with submedian longitudinal ridge. Opposable margin of dactyl with row of 20 knoblike tubercles (first and fifth from base larger than others, latter marking distal end of excised area of finger) decreasing in size from first through fourth and from fifth distally; interrupted row of minute denticles extending distally from sixth tubercle from base to corneous tip of finger; dorsal and ventral surfaces similar to those of fixed finger; mesial surface with cluster of tubercles along proximal three-fifths of finger, contracting to single row reaching slightly beyond base of distal fifth, those along mesialmost margin appearing serrate in silhouette. Carpus about 1.3 times as long as broad with sinuous dorsal sulcus flanked mesially by tubercles and laterally by few tubercles and setiferous punctations; mesial surface with prominent spikelike tubercle, 2 smaller ones proximal to it, and another more dorsally situated and lying proximomesial to articular eminence; ventral surface with 2 large spiniform tubercles on distal margin, more lateral one on condyle, other submedian; 4 additional smaller tubercles present ventromesially. Dorsal surface of merus with 2 spiniform tubercles and several small rounded ones near distal end; ventral surface with lateral and mesial rows of 5 and 12 tubercles, respectively (left with 8 and 12), few of which spikelike; distolateral apophysis with spiniform tubercle, and few additional tubercles immediately distal to fracture line.

Ischium of third pereiopod (Figure 8h) with simple hook overreaching basioischial articulation and opposed by vestige of tubercle on basis; hook heavy and with free end truncate and somewhat flattened. Ventral membrane on coxa of fifth pereiopod studded with short setae.

First pleopods (Figure 8b,f,k) symmetrical and reaching coxa of second pereiopod when abdomen flexed. (See “Diagnosis” for description.)

ALLOTYPIC FEMALE.—Differing from holotype in following respects: acumen overreaching antennular peduncle by one-fifth its length; antennal flagellum reaching base of fifth abdominal segment; ratio of depth to width of chela 0.58, chela distinctly shorter than carapace (20.0 and 30.9 mm); mesial surface of palm of left chela (right regenerated) with 2 rows of tubercles represented by 7 and 5, ventral row absent; opposable margin of fixed finger of chela with row of 8 tubercles (third from base largest) along proximal three-fourths of finger and single tubercle on lower level opposite distalmost member of row; opposable margin of dactyl with row of only 15 tubercles (proximal 5 subequal in size), and distal limit of excision not nearly so distinct as in holotype; setal tufts at base of fixed finger more abundant; mesial surface of carpus with only 2 tubercles, large spikelike one and another smaller at its proximal base; ventral surface of merus with lateral row of 7 tubercles and mesial one of 12. (See Table 4.)

Annulus ventralis (Figure 8d) firmly but not inflexibly fused to sternum, somewhat subrhomboid in outline, about 1.8 times as broad as long, and strongly sculptured with very high transverse ridges interrupted by conspicuously deep median fossa; cephalic third subplane, sloping caudoventrally, and bearing shallow median trough leading caudally which, before reaching fossa, flanked by low longitudinal ridges, latter merging with transverse elevations; caudal slope of ridges occupying caudal half of annulus, its sinistral side steeper than dextral; sinus originating in cephalic part, and on dextral side, of fossa; following dextral extension and making hairpin turn, continuing caudosinistrally to median line where ending on caudal wall of annulus; deeply situated tongue directed dextrally. Postannular sclerite about 3.3 times as broad as long, slightly more than two-thirds as wide as annulus, and only little more than one-third as long. First pleopod reaching cephalically beyond midlength of annulus when abdomen flexed.

MORPHOTYPIC MALE, FORM II.—Differing from holotype in following respects: main body of epistome with less well-defined trough in depressed area; lamella of antennal scale with less angular distomesial margin; ratio of depth to width of chela 0.59, length distinctly less than that of carapace (23.1 and 32.7 mm); mesial surface of palm of chela with rows of setae consisting of 4, 9, and 6 on right member and 4, 7, and 6 on left (latter cheliped probably regenerated); opposable margin of fixed finger with row of 11 tubercles (third from base largest) and 1 on lower level at base of distal third (left member with 14 and 2, respectively); opposable margin of dactyl with row of 20 tubercles (some of which minute and situated dorsal to row of denticles), none on lower level (left member with 24 and 2, respectively); excision of dactyl slightly less conspicuous; tubercles on mesial surface of dactyl more nearly arranged in rows; setal tufts at base of fixed finger more conspicuous and widespread than in holotype; mesial surface of carpus of left cheliped with additional tubercle proximal to spikelike tubercle; ventral surface of merus of right cheliped with 4 tubercles in lateral row and 11 in mesial, that of left with 6 and 16, respectively. Tubercles of chelipeds, other than those on opposable surfaces of fingers, much more acute. Hook on ischium of third pereiopod much reduced, not overreaching basioischial articulation. (See Table 4.)

First pleopod (Figure 8c,e) with more robust rami, and cleft between them conspicuously shorter; juvenile suture present.

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Orconectes holti eller «Bimaculate 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 holti er en av de om lag 85 artene i slekten, og lever i elver og innsjøer nesten utelukkende i Alabama.

Orconectes holti é uma espécie de crustáceo da família Cambaridae.

É endémica dos Estados Unidos da América.