Orconectes cooperi

Orconectes cooperi

DIAGNOSIS.—Body and eyes with pigment. Rostrum with or without median carina, acumen delimited basally by marginal spines or tubercles. Areola 4 to 6 times as long as wide and comprising 25.3 to 29.9 percent of total length of carapace (35.4 to 41.5 percent of postorbital carapace length). Cervical spine small; suborbital angle very weak to obsolete; postorbital ridges moderately well developed with small corneous tubercle cephalically. Antennal scale approximately 2.7 times as long as wide, broadest at about midlength. Chela of adult males conspicuously inflated, not costate laterally; tubercles on mesial margin of palm small and strongly depressed; fingers gaping and conspicuous tuft of setae present along opposable basal part of fixed finger; opposable margin of dactyl not excised in basal third. Hook on ischium of third pereiopod of male. First pleopod of first form male (divisible into carapace length 2.9 to 3.2 times) reaching at least midlength of coxa of second pereiopod when abdomen flexed, without angular shoulder on cephalic surface; terminal elements subparallel and gently recurved along distal fifth; central projection constituting 35 to 38 percent of entire length of pleopod, bladelike and tapering from base to caudodistally directed apex; mesial process subcylindrical in section proximally, troughlike distally, its tip directed caudodistally not extending so far distad as central projection. Annulus ventralis as figured. First pleopod present in female.

HOLOTYPIC MALE, FORM I.—Body and eyes pigmented. Cephalothorax (Figure 7a,i) subovate in section; abdomen narrower than carapace (15.6 and 13.3 mm), width of latter greater than depth at caudodorsal margin of cervical groove (15.6 and 14.8 mm). Areola moderately broad, 7.7 times as long as wide with 4 or 5 punctations across narrowest part; length of areola 28.9 percent of entire length of carapace (38.6 percent of postorbital length). Rostrum with margins little thickened, elevated, and bearing small marginal tubercles at base of acumen, latter reaching slightly beyond distal end of antennular peduncle; upper surface irregular with low median elevation distally and almost entirely punctate. Subrostral ridge weak, disappearing completely in dorsal aspect before reaching midlength of rostrum. Postorbital ridge rather heavy with short dorsolateral groove and terminating cephalically in small, acute, corneous tubercle. Suborbital angle almost obsolete, delimited ventrally by shallow, broad, rounded notch. Cervical spine very small and acute. Carapace densely punctate dorsally and laterally, punctations deep and moderately large, and granulate ventrolaterally. Abdomen longer than carapace (33.5 and 31.8 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 lobe very small, both rami of uropod with median keel ending in spine, that on mesial ramus premarginal.

Cephalic lobe of epistome (Figure 7g) with weak cephalomedian projection and irregular cephalolateral margins, latter elevated (ventrally), ventral surface with scattered setae; main body of epistome, set off from cephalic lobe by distinctly narrow base of latter, bearing deep cephalomedian fovea; epistomal zygoma broadly arched. Proximal segment of antennule provided with large spine near midlength, spine partly concealed by plumose setae extending from ventromesial margin of podomere. Antennal peduncle with small spines on basis and ischium, flagellum reaching tergum of fourth abdominal segment. Antennal scale (Figure 7i,l, latter from allotype) approximately 2.6 times as long as wide, broadest at midlength; thickened lateral area with apical spine reaching slightly beyond distal end of antennular peduncle. Ventral surface of ischium of third maxilliped with thick submarginal lateral row of long plumose setae, and surface between row and median ridge with several thick tufts proximally and scattered shorter ones distally, mesial half studded with dense mat of very long plumose and stiff hairlike setae; distolateral extremity of ischium with distinct corneous spine.

Right chela shorter than carapace (28.4 and 31.8 mm) (Figure 7j), about 2.2 times as long as wide with palm conspicuously inflated (ratio of depth to width 0.71), thickness subequal to length of areola and only slightly less than length of mesial margin of palm; latter with row of 7 very small squamous tubercles extending along proximal three-fourths, tubercles replaced distally by 2 conspicuous punctations; proximal part of row of tubercles flanked dorsolaterally by few additional smaller tubercles, palm otherwise punctate. (Left chela with tubercle on ventral surface opposite base of dactyl.) Fingers gaping, with low submedian longitudinal ridges dorsally and ventrally; fixed finger with conspicuous mat of plumose setae at base and along proximal half of ventromesial surface of finger; opposable margin with row of 6 low, rounded corneous tubercles along basal three-fifths, and large one on lower level at base of distal third; band, very broad distally, of minute denticles extending almost entire length of finger interrupted by members of tubercle row. Opposable margin of dactyl not excised, with row of 9 tubercles similar to those of fixed finger; band of minute denticles extending distally from seventh tubercle and few situated between more proximal tubercles; mesial surface of dactyl punctate, lacking tubercles.

Carpus 1.4 times as long as broad, with oblique dorsomedian furrow; mesial surface with prominent spiniform tubercle flanked proximally by 3 smaller rounded ones; dorsal distomesial angle with small tubercle; ventral surface with scattered punctations and single submarginal tubercle on distal end of articular condyle. Merus with 2 subdistal tubercles dorsally and 1 on ventral distolateral extremity, ventral surface with mesial row of 10 or 11 tubercles and single prominent one as remnant of ventrolateral row; few additional tubercles situated immediately lateral to mesial row; podomere otherwise punctate. Ventromesial margin of ischium with single tubercle.

Ischium of third pereiopod (Figure 7h) with simple hook overreaching basioischial articulation, not opposed by tubercle on basis.

First pleopods (Figure 7b,f,k) symmetrical and extending cephalically to second pereiopod. (See “Diagnosis” for description.)

ALLOTYPIC FEMALE.—Differing from holotype in following respects: abdomen and carapace subequal in width; suborbital angle essentially obsolete; carapace lacking granules except for few in ventral hepatic region and cephaloventral area of branchiostegite; cephalic section of telson with mesial spine in each caudolateral corner broken; left chela (right regenerated) with palm not conspicuously inflated (ratio of depth to width 0.62); mesial margin of palm with irregular row of 9 more elevated tubercles and additional smaller ones dorsolateral to row; opposable margin of fixed finger with row of 6 tubercles, that of dactyl with 10. Spine on dorsal distomesial angle of carpus larger; ventral surface of merus with mesial row of 8 tubercles; 2 tubercles on ventromesial margin of ischium. (See Table 3.)

Annulus ventralis (Figure 7d) moderately deeply embedded in sternum, very slightly movable, suboval in shape and about 1.6 times as broad as long; cephalomedian area elevated and traversed by deep submedian trough; transverse ridge immediately posterior to midlength interrupted by sinistral U-shaped sinus, and tongue extending from dextral ridge; caudal arm of sinus turning caudally on median line and ending on midcaudal wall of annulus; fossa disappearing beneath sinistral arm of transverse ridge. Postannular plate about 4.7 times as broad as long, approximately five-sixths as broad as annulus and about one-third as long. First pleopod reaching cephalic margin of annulus when abdomen flexed.

MORPHOTYPIC MALE, FORM II.—Differing from holotype in following respects: specimen much smaller than holotype or allotype (see Table 3); all spines and tubercles more prominent; chela proportionately smaller in relation to dimensions of carapace; opposable margin of dactyl with only 6 tubercles; merus with 2 spines representing ventrolateral row. Hook on ischium of third pereiopod tuberculiform, not overreaching basioischial articulation. First pleopod (Figure 7c,e) with rami heavier, and cleft between them decidedly shorter.

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