Philomedes duplex Kornicker 1984

Philomedes duplex

Figures 1–8

ETYMOLOGY.—From the Latin duplex (double, twice), referring to the pair of ventral bristles on the 2nd joint of the 1st antenna.

HOLOTYPE.—USNM 157842, adult female, partly dissected, in alcohol.

TYPE-LOCALITY.—R/V Gyre cruise 11, station 9, Gulf of Mexico off Texas.

PARATYPES.—USNM 153939, 154180, 157842–157872, 158231, 158235, 158241, 158243–158245, 158856, 158857, 158860, 158861, 158863, 193034, 193039.

DISTRIBUTION.—Continental shelf off Texas; known depth range 49–134 m (Map 1).

DIAGNOSIS.—Anterior margin of rostrum concave; infold of carapace without “pocket;” length of adult females 1.24–1.33 mm (6 specimens). 2nd joint of 1st antenna of adult female with 1 dorsal bristle, 1 lateral bristle, and 2 (rarely 3) ventral bristles. 1st endopodial joint of 2nd antenna of adult female with 6 short bristles; 2nd joint with 1 long proximal bristle, 1 long or 2 short distal bristles, and 1 recurved terminal bristle. Dorsal margin of mandibular basale with 1 bristle distal to midline and 2 terminal. Seventh limb with 4 proximal bristles (2 on each side) and 5 distal bristles (3 on peg side, 2 on comb side); terminus with comb of about 9 alate teeth opposite 2 short pegs. Each lamella of furca with 10 claws decreasing in length posteriorly along lamella.

DESCRIPTION OF ADULT FEMALE (Figures 1–5).—Carapace oval in lateral view with prominent rostrum and narrow but distinct caudal process (Figure 1); anterior margin of rostrum concave; anteroventral corner of rostrum usually with minute process (Figure 2a,b); edge of valve along dorsal margin of caudal process minutely serrate (Figure 2c); specimens in collection with thin uncalcified valves, but some with minute oval nodules (probably artifacts); posterior margin of carapace concave on some specimens (Figure 1) but linear on others.

Ornamentation: Surface with sparsely distributed long bristles emerging from closed pore with lip; short bristles forming row along edge of caudal process; surface of valve weakly reticulate; long bristles forming row proximal to ventral margin of valve and posterior margin of caudal process (Figure 2c).

Infold: Infold of rostrum with 13–17 bristles, most with marginal spines (Figure 2a,b; all marginal spines not in illustration); infold just ventral to incisur with 1 small bristle; anteroventral infold with 13 or 14 short, stout, spinous bristles along narrow weakly developed list; anteroventral margin proximal to list with about 12 ridges more-or-less parallel to valve edge; middle part of ventral infold with narrow list but no bristles; list on posterior part of ventral infold continuing along posterior infold, and with total of about 34 minute bristles, either singly or in pairs; infold of caudal process between list and valve edge broad, with 5 or 6 small bristles (Figure 2c).

Selvage: Selvage with broad, fringed, lamella prolongation except along posterior edge of caudal process where it becomes narrow; selvage along anterior margin ventral to incisur with long hairs with bases near middle of outer side of lamella prolongation.

Size: USNM 153939, length 1.33 mm, height 0.86 mm; USNM 157842, length 1.31 mm, height 0.90 mm; USNM 157845, length 1.24 mm, height 0.78 mm; USNM 157847B, length 1.33 mm, height 0.87 mm; USNM 157848B, length 1.24 mm, height 0.90 mm; USNM 157848C, length 1.29 mm, height 0.89 mm.

First Antenna (Figure 2d): 1st joint bare. 2nd joint spinous, with 1 dorsal bristle, 1 lateral bristle, and 2 (rarely 3) ventral bristles. 3rd joint short, with few dorsal spines and 3 bristles, 1 ventral, 2 dorsal. 4th joint with 5 terminal bristles, 4 ventral, 1 dorsal. Sensory bristle of long 5th joint with 4 proximal filaments and 4 at tip including stem. Medial bristle of minute 6th joint spinous, about same length as 5th joint. 7th joint: a-bristle spinous, about one and one-half times length of bristle of 6th joint; b-bristle shorter than sensory bristle of 5th joint, with 1 proximal and 4 distal filaments including stem; c-bristle same length as sensory bristle, with 4 or 5 proximal and 4 distal filaments including stem. 8th joint: d- and e-bristles bare with blunt tips, about same length as sensory bristle; f-bristle longer than b-bristle, with 4 proximal and 4 distal filaments including stem; g-bristle same length as sensory bristle, with 3 or 4 proximal and 4 terminal filaments including stem.

Second Antenna: Protopodite bare. Endopodite 2-jointed (Figure 2e): 1st joint short with 6 short bristles, 5 proximal, 1 distal; 2nd joint elongate with 1 long proximal ventral bristle and either 1 long or 2 short distal ventral bristles, and 1 recurved terminal bristle (right endopodite of USNM 153939 aberrant, Figure 2f). Exopodite: bristles of joints 2–5 fairly short, bare; bristles of joints 6–8 long, with natatory hairs; 9th joint with 7 bristles (3 short, 4 long), all with natatory hairs; 1st joint with minute terminal medial bristle with open tip; joints 2–8 with minute spines forming row along distal margin and basal spines increasing in size on distal joints; basal spine on joint 8 reaching past distal end of joint 9; lateral spine not observed on 9th joint.

Mandible (Figure 3a): Coxale endite bifurcate, spinous, with minute bristle near base. Basale: dorsal margin with 1 bristle distal to middle and 2 terminal (of these, lateral bristle about one-half length of medial bristle); medial surface hirsute, with 7 proximal bristles (3 pectinate and 3 spinous near middle, and 1 spinous near ventral margin), and 1 spinous distal bristle near ventral margin; ventral margin with 5 spinous bristles (longest of these distal to others). Exopodite hirsute, about three-fourths length of distal margin of 1st endopodial joint, with 2 subterminal bristles. 1st endopodial joint with 4 ventral bristles (1 of these very short). 2nd endopodial joint: ventral margin with bristles forming 2 distal groups (3 bristles in each group); dorsal margin with 12 bristles more-or-less forming 2 groups near middle (some of these bristles with bases on medial or lateral sides of joint); medial surface with spines forming rows. 3rd endopodial joint with 3 claws with ventral teeth, and 4 bristles.

Maxilla (Figure 3b): Endite I with 9 bristles; endite II with about 6 bristles;endite III with about 9 distal bristles and 1 proximal bristle; endites I and II shorter than endite III; endite I broader than endites II and III. Precoxale and coxale with dorsal lamellar prolongation with hirsute fringe. Coxale with spinous dorsal bristle. Basale with 3 distal bristles (dorsal of these short). Exopodite short, with 3 terminal bristles (2 long, 1 short). Endopodite: 1st joint with 1 spinous alpha-bristle and 5 beta-bristles; end joint with 3 pectinate claw-like bristles and about 9 ringed bristles (beta-bristles and most bristles on end joint not shown on illustrated limb).

Fifth Limb (Figure 4): Endite I with 6 bristles; endites II and III each with about 8 bristles. 1st expodial joint: anterior side with 2 bristles (1 of these with few long spines); main tooth with stout bifurcate tooth anterior to large club-like tooth followed by 2 pectinate and 1 smooth tooth and 1 proximal, spinous bristle. 2nd exopodial joint: anterior side of large squarish tooth with small spinous bristle in distal outer corner and small bristle on lobe proximal to outer distal corner (lobe may be on 1st joint); posterior side of joint obscure but with 3 or 4 bristles. Outer lobe of 3rd exopodial joint with 2 spinous bristles, inner lobe with 3 bristles. Fused 4th and 5th exopodial joints with total of 7 spinous bristles. Epipodial appendage with 45 bristles.

Sixth Limb (Figure 5a): Endite I with 1 long, spinous, terminal bristle and 2 short, spinous, medial bristles; endite II with 3 spinous terminal bristles and 1 short, spinous, medial bristle; endites III and IV each with 8 terminal bristles and 1 short, spinous, medial bristle; end joint projecting posteriorly, with 16 or 17 spinous and hirsute bristles; 3 hirsute bristles in place of epipodial appendage.

Seventh Limb (Figure 5b): Each limb with 4 proximal bristles (2 on each side) and 5 distal bristles (3 on peg side, 2 on comb side); each bristle with 3–5 bells and distal marginal spines; terminus with comb of about 9 alate teeth opposite 2 short pegs.

Furca: Each lamella with 10 claws decreasing in length posteriorly along lamella; hairs present medially at base of claw 1 and also following claw 10; posterior margin of claw 1 with stout teeth alternating with 1 or 2 small teeth; remaining claws with teeth along posterior margins.

Bellonci Organ (Figure 5c): Elongate with suture near middle and rounded tip.

Eyes (Figure 5c): Medial eye light amber, bare. Lateral eyes minute, each with 2 amber ommatidia.

Upper lip (Figure 5c): Hirsute with anterior projection with faint processes.

Y-Sclerite (Figure 5d): Ventral branch almost forming right angle with dorsal branch.

Genitalia: Small oval area colored pink with Rose-Bengal dye, on each side of body anterior to furca.

Eggs: USNM 153939 with about 10 unextruded eggs; USNM 157845 with 4 eggs in marsupium.

DESCRIPTION OF ADULT MALE (Figures 6–8).—Carapace more elongate than that of adult female, with incisur forming right angle, and with broadly convex margin on rostrum (Figure 6).

Size: USNM 154180, length 1.31 mm, height 0.68 mm; USNM 157844A, length 1.34 mm, height 0.74 mm; USNM 157844B, length 1.25 mm, height 0.66 mm; USNM 157847A, length 1.30 mm, height 0.65 mm; USNM 157848A, length 1.33 mm, height 0.60 mm; USNM 158231, length 1.27 mm, height 0.68 mm.

First Antenna (Figure 7a): 1st joint bare. 2nd joint spinous, with 4 bristles (2 ventral, 1 dorsal, 1 lateral). 3rd joint short, spinous, with 3 bristles (1 ventral, 2 dorsal). 4th joint elongate, with few spines and 5 bristles (4 ventral, 1 dorsal). 5th joint small, wedged ventrally between 4th and 6th joints; sensory bristle with stout stem with 5 short terminal filaments and abundant long proximal filaments. Medial bristle of long 6th joint with long spines near middle. 7th joint: a-bristle short spinous; b-bristle broken on specimen studied; c-bristle very long, with 13 marginal filaments. 8th joint: d- and e-bristles bare, tips broken on USNM 154180; f-bristle very long, with about 12 marginal filaments; g-bristle broken on USNM 154180.

Second Antenna (Figure 7b): Protopodite bare. Endopodite 3–jointed: 1st joint short with 6 bristles (5 proximal, 1 distal); 2nd joint elongate, with 3 midbristles; 3rd joint elongate, reflexed on 2nd, with 1 proximal bristle (about same length as midbristles of 2nd joint) and 2 subterminal bristles; tip with 5 or 6 ridges. Exopodite: 1st joint with faint spines forming rows along concave margin, and minute terminal medial bristle; 2nd joint about half length of third but wider; joints 4–9 small, decreasing in width distally along stem; bristle of 2nd joint fairly short (reaching 7th joint), with ventral spines but no natatory hairs; bristles of joints 3–8 with natatory hairs; 9th joint with 6 bristles (2 short, 1 medium, 3 long), all with natatory hairs; joints 3–8 with narrow basal spines increasing in length distally along stem; basal spine of 8th joint same length as 9th joint; no lateral spine observed on 9th joint; joints 2–8 with minute spines forming row along distal margin.

Mandible (Figure 7c, d): Coxale endite minute, bifurcate distally, but without spines; minute bristle just distal to endite. Basale: dorsal margin with 1 bristle distal to middle and 2 terminal (of these, lateral bristle about one-third length of medial bristle); medial surface hirsute, with 7 spinous proximal bristles near ventral margin (1 closer to ventral margin than others); ventral margin with 4 spinous bristles (distal of these longer than others); lateral surface with 1 spinous bristle near middle of ventral margin. Exopodite hirsute, about two-thirds length of distal margin of 1st endopodial joint, with 2 subterminal bristles. 1st endopodial joint with 4 or 5 ventral bristles (1 or 2 of these very short); medial surface with short spines forming rows. 2nd endopodial joint: ventral margin with bristles forming 2 distal groups (3 bristles in each group); dorsal margin with bristles forming 2 groups near middle (5 or 6 bristles in proximal group, 6 in distal group); medial surface with spines forming rows. 3rd endopodial joint with 3 claws with ventral teeth (ventral teeth not shown on illustration), and 4 bristles.

Maxilla (Figure 7e): Reduced; coxale endites and endite bristles weakly developed; coxale with fringed lamella prolongation along dorsal margin and stout hirsute dorsal bristle; basale with 3 bristles. Exopodite with 3 hirsute bristles (2 long, stout; 1 short). Endopodite: 1st joint hirsute, with 1 alpha-bristle near middle of anterior margin, and 4 or 5 beta-bristles; 2nd joint with many weakly developed bristles.

Fifth Limb (Figure 8a): Epipodial appendage with 45 bristles. Endites and exopodite weakly developed. Endites I–III with numerous weakly developed bristles. Exopodite: 1st joint with 2 finger-formed bristles and several slender bristles, all weakly developed; 2nd joint with sclerotized finger-formed bristle and several weakly developed bristles; 3rd joint with 3 short slender bristles on inner lobe and 2 long bristles on outer lobe, all bristles hirsute; joints 4 and 5 fused, with total of 5 hirsute bristles.

Sixth Limb (Figure 8b): Endite I with 3 bristles; endite II with 4 bristles (I medial, 3 terminal); endite III with 9 bristles (1 medial, 8 terminal); endite IV with 8 bristles (1 medial, 7 terminal); medial bristle and posterior terminal bristle of endites hirsute, others bare. End joint projecting posteriorly, with 13 bristles (mostly hirsute) along ventral margin. 3 short hirsute bristles present in place of epipodial appendage.

Seventh Limb (Figure 8c): Each limb with 6 proximal bristles (3 on each side) and 5 distal bristles (3 on peg side, 2 on comb side); each bristle with 4 or 5 bells and distal marginal spines; terminus with comb of about 10 alate teeth opposite 2 short pegs.

Furca: Similar to that of female.

Bellonci Organ (Figure 8d,e): Similar to that of female.

Eyes (Figure 8d,e): Medial eye bare, with a few spots of light pigment. Lateral eye slightly larger than medial eye, pigmented light amber, with about 13 ommatidia.

COMPARISONS.—The only previously described species of Philomedes with a pair of bristles on the ventral margin of the 2nd joint of the 1st antenna is P. lofthousae Kornicker, 1975;281. The latter species is much larger than P. duplex, the dorsal margin of the 2nd joint of the 1st antenna of the adult female bears 2 bristles rather than 1; and the dorsal margin of the mandibular basale bears 4 bristles rather than 3.