Pseudophilomedes polyancistra Kornicker 1984

Pseudophilomedes polyancistrus

ETYMOLOGY.—From the Greek polyankistros (with many hooks) in reference to the hook-like prongs on the inner margin of the large tooth forming the 2nd exopodial joint of the female 5th limb.

HOLOTYPE.—USNM 158047, ovigerous female, partly dissected, in alcohol.

TYPE-LOCALITY.—R/V Gyre, cruise 11, station 2, Gulf of Mexico.

PARATYPES.—USNM 158032, 158034–158039, 158041–158048, 158306, 158408, 158854, 158859.

DISTRIBUTION.—One specimen was collected in the Atlantic on the continental shelf off northern Florida (30°23′N, 80°10′W) at a depth of 147 m. Additional specimens were collected in the Gulf of Mexico off Florida and Texas (Map 2). Known depth range 15–147 m.

DIAGNOSIS.—Posterior end of carapace with slight projection of caudal process in female, greater projection in adult male (Figures 23, 26); infold of rostrum with 3 long bristles (Figure 24a); infold of caudal process with 4 frond-like bristles (Figure 24b); length of adult female 0.89–1.00 mm (6 specimens). Exopodite of 2nd antenna with natatory bristles. 2nd exopodial joint of maxilla of adult female with 2 bristles (1 long, 1 short) and a stout finger-like terminal process (Figure 24f). Exopodite of 5th limb of female: distal tooth of 1st joint with 3 prongs; 2nd joint prolonged to form curved tooth with total of 7 both proximal and distal hook-like prongs (3 large, 4 small) along inner margin (Figure 24g). 7th limb of adult female with 2 proximal bristles (1 on each side) and 6 distal bristles (3 on each side) (Figure 24i); male without 7th limb. Each lamella of furca with 6 or 7 claws; claw 3 thinner and shorter than claw 4; claw 1 of female with slender medial tooth near middle (Figure 25a).

DESCRIPTION OF ADULT FEMALE (Figures 23–25).—Carapace elongate with triangular rostrum, and caudal process indicated by very slight projection just below middle of posterior margin (Figures 23, 24b, 25e); ventral margin of rostrum forming obtuse angle with anterior margin of valve below rostrum.

Ornamentation (Figure 23): Surface of valve appearing smooth but minute shallow fossae visible on some specimens, and minute rimmed pores visible at high magnification (40 × objective). Long bristles present along anterior and ventral margins and sparsely distributed over lateral surface.

Infold: (Figure 24a,b) Rostral infold with 3 long bristles forming row and 1 small bristle near inner end of incisur (Figure 24a); anteroventral margin with 1 small bristle; infold of caudal process with 4 spinous bristles (Figure 24b); inner edge of infold along anterodorsal and dorsal margins in vicinity of caudal process with several minute bristles. (Right valve of USNM 158047 unusual in having only 2 spinous bristles on infold of caudal process.)

Selvage (Figure 24a): Selvage with broad lamellar prolongation with fringed margin present along anterior and ventral margins; prolongation not divided in vicinity of incisur. Fringed lamellar prolongation also present along posterior margin but may be absent along edge of caudal process.

Size: USNM 158036 (one of the specimens with this number), length 0.98 mm, height 0.65 mm; USNM 158041, length 0.89 mm, height 0.64 mm; USNM 158047, length 0.96 mm, height 0.66 mm; USNM 158306, 2 specimens: length 0.94 mm, height 0.59 mm and length 0.98 mm, height 0.60 mm; USNM 158408 (carapace of adult female with animal removed), length 1.00 mm, height 0.65 mm.

First Antenna (Figure 24c): 1st joint with few lateral spines forming rows. 2nd joint with 1 dorsal bristle (on illustrated right limb dorsal bristles on joints 2–4 appear to be on medial side some distance from dorsal margin; these bristles are on dorsal margin of left limb of same specimen), few dorsal spines forming rows (appear medial on illustrated limb), and distal lateral spines forming row. 3rd joint short, with 2 bristles (1 ventral, 1 dorsal, and few spines near base of ventral bristle). 4th joint with 3 bristles (1 dorsal, 2 ventral) and few ventral spines forming row. Sensory bristle of 5th joint with short proximal filament and double spine at tip (tip broken off on illustrated limb). Minute 6th joint fused to 5th, with short spinous medial bristle. 7th joint: a-bristle spinous, about 3 times length of bristle of 6th joint; b-bristle same length as a-bristle (USNM 158041), or one-third longer than a-bristle (USNM 158408), bare except for spine at tip; c-bristle same length as sensory bristle of 5th joint, bare except for double spine at tip. 8th joint: d- and e-bristles bare with blunt tips, about same length as c-bristle; f-bristle shorter than c- bristle, with minute proximal filament and double spine at tip; g-bristle same length as c-bristle, with 2 minute proximal filaments and double spine at tip.

Second Antenna (Figure 24d): Protopodite bare. Endopodite weakly 2-jointed. 1st joint with 2 short proximal anterior bristles; small 2nd joint with long spinous terminal bristle. Exopodite: long 1st joint with minute medial bristle on distal margin; bristle of short 2nd joint with hair-like proximal spines along ventral margin and long distal hairs along ventral and dorsal margins; bristles of joints 3–8 similar to that of 2nd joint except longer; 9th joint with 3 bristles (1 long and 1 medium similar to bristle of 2nd joint, 1 short, with short marginal hairs); joints 2–8 with minute spines along distal margins; basal spines absent.

Mandible (Figure 24e): Coxale endite elongate with bifurcate and pectinate tip. Basale: dorsal margin with 3 bristles (1 just distal to middle, 2 terminal); medial surface with 1 or 2 bristles (1 proximal, 0 or 1 distal) near ventral margin or midway between ventral and dorsal margins, and 2 distal bristles (1 short, 1 very long) on or near ventral margin; medial and lateral surfaces of joint with spines forming rows. Exopodite reaching to middle of 1st endopodial joint, with 2 terminal bristles. 1st endopodial joint with medial spines forming rows; ventral margin with 3 bristles (1 minute; 2 long, spinous). 2nd endopodial joint: medial surface spinous; lateral surface with distal spines forming row; dorsal margin with 3 or 4 bristles near middle; ventral margin with 2 small distal bristles; end joint with 2 claws (1 long lateral, 1 medial and ventral about two-thirds length of long claw) and 3 ringed bristles (1 short, medial to long claw; 1 lateral to and about same length as smaller ventral claw; 1 ventral, short).

Maxilla (Figure 24f): Endite I with 2 pectinate claws and 2 ringed bristles; endite II with 2 pectinate claws and 2 ringed bristles; endite III small, with 2 small bristles. Dorsal margins of precoxale, coxale, and basale with fringe of long hairs. Coxale with dorsal bristle with stout proximal part. Basale with 3 bristles on distal margin (2 ventral, 1 dorsal). Exopodite consisting of 3 subequal bristles on lateral side of limb. Endopodite: 1st joint spinous, with 1 or 2 distal bristles; 2nd joint with finger-like terminal process and 2 bristles (1 short, 1 long).

Fifth Limb (Figures 24g, 25f–h): Single endite with 1 or 2 short bristles. 1st exopodial joint with 2 teeth: proximal tooth with 3 pectinate prongs and 2 short bristles; distal tooth with 3 pectinate prongs. 2nd exopodial joint prolonged to form curved tooth with 7 hook-like prongs (3 large, 4 small) along inner margin; 2 bristles present proximal to teeth along inner margin (1 of these could be on inner lobe of 3rd joint). 3rd exopodial joint with 2 hirsute bristles on outer lobe. 4th and 5th joints fused, hirsute, with 3 terminal bristles.

Sixth Limb (Figure 24h): Endite I with 2 short spinous bristles; endite III with 1 long spinous bristle; endite III with 5 spinous bristles; endite IV with 4 spinous bristles. End joint with 7 spinous bristles followed by 2 hirsute bristles.

Seventh Limb (Figure 24i): Each limb with 2 proximal bristles, 1 on each side, and 6 distal bristles, 3 on each side; each bristle with up to 4 bells and marginal spines; terminus consisting of opposing combs having 3 and 5 teeth.

Furca (Figure 25a): Each lamella with 6 or 7 claws; claw 3 shorter and more slender than claw 4 (some specimens without short 3rd claw); claw 4 followed by 2 or 3 smaller claws decreasing in length proximally along lamella; several sets of spines on each lamella following last claw; claw 1 with slender medial tooth near middle.

Bellonci Organ (Figure 25b,d,i): Elongate with about 5 proximal sutures, widening in middle, with broad tip with pointed spine or spines. Minute spines present on distal half visible at high magnification (100 × objective; Figure 25b).

Eyes: Medial eye with small amount of brown pigment, tapering distally (Figure 25d,i). Lateral eye about one-half diameter of medial eye, with dark brown pigment and 3 ommatidia (Figure 25c,d,i).

Genitalia (Figure 25a): Oval sclerotized ring on each side of body anterior to furca.

Posterior of Body (Figure 25a): Without spines, hairs, or processes.

Y-Sclerite (Figure 25a): Branching distally.

Eggs: USNM 158041 with 2 eggs in marsupium, USNM 158047 with 6 eggs in marsupium.

Parasites: USNM 158408, adult female, with choniostomatid copepod within carapace.

DESCRIPTION OF ADULT MALE (Figures 26, 27).—Carapace oval in lateral view, with small rostrum and caudal process (Figure 26, 27a); ventral margin of rostrum forming slightly obtuse angle with valve margin ventral to rostrum.

Ornamentation (Figure 26): Each valve with depressed sulcus near middle; surface appearing smooth at low magnification but with faint shallow fossae and minute protuberances; surface with widely scattered bristles; bristles forming row along anterior and ventral margins; 3 or 4 long bristles, some divided, near edge of caudal process.

Infold: Rostral infold with 3 long bristles forming row and 1 small bristle near inner end of incisur; infold of caudal process with at least 4 frond-like bristles forming row; anteroventral infold with 1 small bristle near middle; additional small bristles present along inner edge of posteroventral infold.

Selvage: Similar to that of female.

Size: USNM 158048, length 0.91 mm, height 0.56 mm.

First Antenna (Figure 27b): 1st joint with few lateral distal hairs. 2nd joint with few hairs and spines forming rows, and 1 dorsal bristle with base on medial surface of joint. 3rd joint short, with 1 ventral and 1 dorsal bristle, both with bases on medial surface, and distal lateral spines forming row. 4th joint elongate with 1 dorsal bristle with base on medial surface. 5th joint small, wedged ventrally between 4th and 6th joints; sensory bristle with broad base with backward pointing proximal end and abundant filaments; stem of sensory bristle with 3 marginal filaments and bifurcate tip. Elongate 6th joint with distal medial bristle almost same length as joint. 7th joint: a-bristle almost twice length of bristle of 6th joint, bare except for spine at tip; b-bristle about twice length of a-bristle, with 3 marginal filaments and bifurcate tip; c-bristle stout, about twice length of b-bristle, with about 11 marginal filaments. 8th joint: d- and e-bristles bare with blunt tips, longer than b-bristle; f-bristle slightly shorter than c-bristle, longer than d- and e-bristles, with about 10 marginal filaments, some pectinate; g-bristle about same length as d- and e-bristles, with 5 marginal filaments and bifurcate tip.

Second Antenna (Figure 27c,d): Protopodite bare. Endopodite 3-jointed (Figure 27c): 1st joint short with 3 anterior bristles; 2nd joint elongate with 1 ventral bristle distal to middle; 3rd joint elongate, tapering to rounded tip, with 2 small spinous bristles near tip. Exopodite (Figure 27d): 1st joint elongate with small recurved medial spine terminally; joints 2–9 short, decreasing in length distally along limb; bristles of joints 2–8 long with natatory hairs; 9th joint with 3 or 4 bristles (1 short with short marginal spines; 0 or 1 medium; 2 long with natatory hairs); joints 2–9 with spines forming row along distal margins (only on lateral side of joint 9); no basal spines.

Mandible (Figure 27e): Coxale endite consisting of small medial spine. Basale: dorsal margin with 3 bristles (1 near middle, 2 terminal); ventral margin with 2 bristles (1 short, near middle; 1 long, distal); medial side with 2 short bristles with bases closer to ventral than to dorsal margin. Exopodite about one-half length of dorsal margin of 1st endopodial joint, with 2 long terminal bristles. 1st endopodial joint with 3 ventral bristles (2 long, 1 short). 2nd endopodial joint: ventral margin with spines and 2 short distal bristles; dorsal margin with 4 bristles (1 proximal, 3 near middle). End joint with 1 long stout claw, 2 short ventral bristles, and 2 lateral bristles (the longer of these weakly ringed, claw-like).

Maxilla (Figure 27f): Limb reduced. Precoxale, coxale, basale with fringe of long hairs along dorsal margin. 3 small endites with weakly developed bristles, some finger-like without rings; endites I and II elongate with 3–5 bristles; endite III short with 2 or 3 small bristles. Coxale with 1 long bristle near dorsal margin. Basale with 1 long bristle near dorsal margin and 1 long and 1 short ventral bristle near margin. Expopodite consisting of 3 long bristles near distal margin of basale. Endopodite: 1st joint hirsute, with 1 long, ringed, alpha-bristle; 2nd joint with 3 ringed terminal bristles (longest of these with many spines).

Fifth Limb (Figure 27g): Epipodial appendage with 38 or 39 bristles. Single endite with 2 bristles (1 ringed, 1 unringed). Exopodite: 1st joint with small bristles (2 unringed, 3 ringed); 2nd joint with 2 proximal, small, finger-like processes and 1 distal, spinous, ringed bristle; inner lobe of 3rd joint with 1 short bristle, outer lobe with 2 long bristles; fused 4th and 5th joints hirsute, with 3 ringed bristles.

Sixth Limb (Figures 27h): Endite I with 2 short bristles; endite II with 1 longer hirsute bristle; endite II with 5 spinous and hirsute bristles; endite IV with 4 spinous and hirsute bristles. End joint with 6 or 7 spinous bristles followed by 2 stout hirsute bristles. Limb hirsute.

Seventh Limb: Absent.

Furca (Figure 27i): Each lamella with 6 or 7 claws; claw 3 shorter and more slender than claw 4; several sets of spines on each lamella following last claw; each claw with teeth along posterior edge; no large medial tooth present on claw 1.

Bellonci Organ (Figure 27j): Elongate with about 6 proximal sutures, broadening near middle, then tapering to narrowly rounded tip.

Eyes: Medial eye with few spots of brown or black pigment (Figure 27j). Lateral eye about same size as medial eye, with brown or black pigment and about 11 divided ommatidia (Figure 27k).

Genitalia (Figure 27i): Elongate with lobes at tip, some bearing small sclerotized processes and bristles.

Y-Sclerite (Figure 27i): Branching distally.

REMARKS CONCERNING JUVENILES.—USNM 158043, A–1 female (length 0.80 mm, height 0.57 mm) and USNM 158042, A–1 male (length 0.84 mm, height 0.57 mm), both with natatory hairs on exopodial bristles of 2nd antennae. The latter without 7th limbs.

SEXUAL DIMORPHISM.—In addition to usual differences between males and females of this genus, the male of P. polyancistrus is without 7th limbs.

COMPARISONS.—The new species differs from previously described species of the genus in females and juveniles having secondary teeth distally as well as proximally along the inner margin of the prolonged tooth of the 2nd exopodial joint of the 5th limb.