Pseudorchomene debroyeri, D’Acoz, Cedric D’Udekem & Havermans, Charlotte, 2012

D’Acoz, Cedric D’Udekem & Havermans, Charlotte, 2012, Two new Pseudorchomene species from the Southern Ocean, with phylogenetic remarks on the genus and related species (Crustacea: Amphipoda: Lysianassoidea: Lysianassidae: Tryphosinae), Zootaxa 3310, pp. 1-50 : 18-28

Pseudorchomene debroyeri sp. n.

( Figs 10–16 )

Pseudorchomene coatsi . — De Broyer, 1983: 193 –195, figs. 72–74. Not Orchomenopsis coatsi Chilton, 1912: 477 , pl. 1, fig. 8–9.

Type material specimens. “ICEFISH” cruise, Falkland Islands, S of Beauchene Island, sta. 14, trap 3, 53°02'32"S 59°08'03"W – 53°26'24"S 59°08'39"W, 470 m, 26.v.2004: 1 HOLOTYPE female, USNM 1156918, dissected and mounted on 20 slides in Euparal, and 18 PARATYPES in alcohol, USNM 1156919, Specimen Ids with corresponding GenBank accession numbers: PD–1105108 ( JQ423241 ), PD–1105109 ( JQ423242 ). — R/V “Polarstern” cruise ANT–XIX/5 (LAMPOS), Burdwood Bank, sta. 147–1, 54°32'S 55°55'W, 413 m, baited traps, 06.iv.2002: 30 PARATYPES, Specimen Ids with corresponding GenBank accession numbers: PD–081007202B ( JQ423244 ), PD– 221007142B ( JQ423243 ), RBINS, INV. 100955.(2 tubes).

Additional material. Expedition KER 82, sta. N4, Fosse de l'Hydrographie, between île Suhm and Port Douzième, 49°30'00"S 70°10'00"E, 90 m, 18–29.i.1982: 1 female, leg. C. De Broyer, RBINS, INV. 100968 (2 tubes). — Expedition KER 82, sta. N6, between île Heugh and îles Gibson, label inside vial indicating 'Narres', 49°00'00"S 69°00'00"E, 140 m, 08–09.ii.1982: about 100 specimens (one female partly dissected but not permanently mounted), leg. C. De Broyer, RBINS, INV. 100972. — Expedition KER 82, sta. N8, 'near Port Bizet, fosse de Green', 49°31'00"S 69°54'00"E, 100 m, 08–09.ii.1982, about 30 specimens, leg. C. De Broyer, RBINS, INV. 100967. — Expedition KER 82, sta. N10, 'along Fosse de Channer', 49°S 69°E, 55 m, 23–24.ii.1982: 10 specimens, leg. C. De Broyer, RBINS, INV. 100971. — Expedition KER 82, sta. N10, 'along Fosse de Channer', 49°S 69°E, 55 m, 23–24.ii.1982: 3 specimens, leg. C. De Broyer, RBINS, INV. 100966.

Type locality. Falkland Islands, south of Beauchene Island, 53°02'32"S 59°08'03"W – 53°26'24"S 59°08'39"W, 470 m.

Etymology. The species is dedicated to Claude De Broyer, who provided good illustrations of the species under the name P. coatsi ; see De Broyer (1983). The name is a genitive.

Diagnosis. Somites of pereon and pleosome without posterior humps. Mandibular palp inserted well proximal to molar process. Molar process broad. Gnathopod 1: anterior margin of basis convex, palm transverse, basis 2.4 x, ischium 3.5 x, carpus 3 x, propodus 3.5 x as long as wide. Gnathopod 2: carpus 3.0 x as long as wide. Pereopod 3: propodus with about 16–18 spines or pairs of spines (which are well developed). Pereopod 3–7: on propodus, broadest spine of each pair or triplet with tip pointed. Coxa 4 posteroventrally rounded. Pereopod 5: coxa distinctly broader than long; basis strongly expanded; merus with setae posteriorly and one distal fairly slender posterodistal spine. Ratio length/width of merus of pereopods 5–7: 1.8; 2.3; 2.6. Ratio length/width of carpus of pereopods 5–7: 1.7; 2.6; 2.4. Posterodistal angle of carpus of pereopods 5–7 with spines of normal length and stoutness. Pereopod 7: anterior margin of carpus with spines longer and more numerous than in other species, posterior margin of carpus and often of propodus with non-distal spine(s). Epimeron 3 regularly rounded posteriorly. Uropod 3: medial margin of both rami with many long setae, inner ramus not reaching tip of article 1 of outer ramus.

Description. Based on HOLOTYPE female, “ICEFISH” cruise, Falkland Islands, S of Beauchene Island, station 14, trap 3, 53°02'32"S 59°08'03"W – 53°26'24"S 59°08'39"W, 470 m, USNM 1156918.

Body without dorsal carina; somites of pereon and pleosome without small posterior humps. Head: lateral cephalic lobes broadly rounded.

Eyes occupying the most of anterior part of head, much longer than broad, lower part much broader than upper part, distinctly concave anteriorly, nearly straight posteriorly, dark, with fully developed ommatidia.

Antenna 1 distinctly shorter than antenna 2; major flagellum 18-articulate, first article 0.4 x as long as entire flagellum; accessory flagellum 7-articulate, article 1 elongate, slightly longer than 6 distal articles combined; calceoli absent.

Antenna 2 about 0.2 x as long as body; peduncular articles 3 to 5 not enlarged, with brush of setae; flagellum 42-articlulate; calceoli absent.

Mouthparts forming a quadrate bundle. Epistome carinate, scarcely produced, terminating in small blunt tooth; upper lip broadly rounded, distinctly overreaching epistome.

Mandible: incisor process, cutting edge smooth, except for small blunt denticle on each side, lateral and medial borders parallel; lacinia mobilis present on left side only, narrowly cylindrical (finger-like), slightly curved, distally slightly dilated with 6 well-developed dentiform processes; 3 small raker spines and a dense patch of short setules present between incisor and molar processes; molar process broad, elliptic to subovate, transversally ridged and triturative; lateral setigerous crest arising from proximal 0.3 of molar process; palp 3-articulate, attached midway, well proximal to molar process; article 1 without setae, article 2 longest with row of 25 strong distal and subdistal A2-setae, article 3 of palp 0.70 x as long as article 2, 4.1 x as long as wide, with 1 proximal A3-seta, a row of 29 D3-setae on distal 0.7 (these setae are slightly shorter than width of article 3), and 4 E3-setae.

Maxilla 1: inner plate very elongate, distally very narrow, with 3 stout setae [one is much more slender than the others] in truly distal position; outer plate with 11 blade-shaped spines (in 7/4 arrangement), which are denticulate on one side; palp 2-articulate, broad with distal row of 13 cuspidate spines anteriorly and a stout antero-distal flag seta.

Maxilla 2: plates very narrow, tapering; inner plate much shorter and slightly narrower than outer plate.

Maxilliped: inner and outer plates well developed; inner plate narrow, about half the length of outer plate, with well-developed posteromedial row of strong setae, 3 apical nodular spines and 1 anterodistal stout seta; outer plate overreaching tip of article 2 of palp, with lateral double row of long setae, 2 distal large stout blunt spines, a medial row of 28 much smaller low nodular spines, and 19 small slender facial (isolated or paired) spines; dactylus well developed.

Gills: long accessory process on gill of pereopods 5–6; gill of pereopod 7 well developed and posteriorly pointed.

Oostegites: linear, from gnathopod 2 to pereopod 5.

Gnathopod 1: subchelate; coxa large but slightly shorter than coxa 2, externally visible, triangular, anterior and posterior margins nearly straight and strongly divergent, ventral margin broad and distinctly convex; all articles except merus and dactylus elongate; basis strongly convex anteriorly and weakly convex posteriorly, with many long setae along anterior margin, 2.4 x as long as wide; ischium moderately elongate, 3.5 x as long as wide; merus triangular, 2.5 x as long as wide, a bit shorter than ischium and carpus; carpus moderately elongate, 3 x as long as wide; propodus linear, 3.5 x as long as wide and slightly longer than carpus, palm transverse and minutely denticulate; dactylus well developed.

Gnathopod 2: minutely chelate; coxa large but slightly shorter than coxa 3, subrectangular; ischium 3.4. x as long as wide; carpus 3.0 x as long as wide, 2.2 x as long as propodus, anterior margin with dense row of very short setae beyond midlength, and many long setae distally; propodus strongly convex anteriorly with many long setae, weakly concave posteriorly with many very short setae, palm with a cavity and an extended inner dentate basket; dactylus very short, denticulate, reaching corner of palm.

Pereopod 3: coxa large, about as long as coxa 4, subrectangular, posterior margin slightly concave; ischium, merus and carpus with many long setae posteriorly; merus slightly expanded anteriorly, 2.8 x as long as wide; carpus 3.7 x as long as wide and 0.73 x as long as merus; propodus 6.3 x as long as wide, 1.4 x as long as carpus, with 18 well-developed spines (or pairs of spines) posteriorly, the largest spines of each group acute-tipped and with accessory branch; dactylus normally developed, curved, with long unguis, 0.31 x as long as propodus.

Pereopod 4: coxa deeper than wide, posteroventral lobe large, posteroventral corner of lobe more or less rounded (with slight angular discontinuity); ischium, merus and carpus with many long setae posteriorly; merus slightly expanded anteriorly, 2.8 x as long as wide; carpus 3.6 x as long as wide and 0.53 x as long as merus; propodus 4.7 x as long as wide, 1.4 x as long as carpus, with about 16 well-developed spines (or pairs of spines) posteriorly, the largest spines of each group acute-tipped and with accessory branch; dactylus normally developed, curved, with long unguis, 0.35 x as long as propodus.

Pereopod 5: coxa broader than long, weakly bilobate, posterior lobe not produced ventrally, 1.3 x as long as basis; basis strongly expanded posteriorly, about as long as broad, with 26 short spines anteriorly, 16 weak but distinct crenellations posteriorly, posteroventral lobe well developed and broadly rounded; ischium with 2 groups of short spines anteriorly, the distal one associated with a long seta; merus expanded, 1.8 x as long as broad, anterior margin straight, posterior margin convex, bearing 6 long setae and 1 distal medium-sized spine; carpus 1.7 x as long as broad, with 3 posterodistal slender spines of normal length; propodus 5.9 x as long as broad, 1.9 x as long as carpus, with 11 acute spines (or pair of spines) anteriorly, each spine with accessory branch (except those of distal pair); dactylus normally developed, curved, with long unguis, 0.38 x as long as propodus.

Pereopod 6: coxa slightly concave anteriorly, convex posteriorly, distinctly bilobed, shorter than coxa 5, 1.4 x as long as broad, 0.88 x as long as basis; basis longer than basis of pereopod 5, expanded posteriorly, 1.5 x as long as broad, with 10 short marginal spines or groups of spines (and some submarginal spines) anteriorly, 20 weak but distinct crenellations posteriorly, posteroventral lobe well-developed and broadly rounded; ischium–dactylus combined slightly longer than in pereopod 5 and as long as in pereopod 7; ischium with 7 spines and 3 long setae on anterior margin; merus weakly expanded, 2.3 x as long as broad, anterior margin nearly straight, posterior margin weakly convex bearing 6 isolated small spines of normal stoutness; carpus 2.6 x as long as broad, with 1 short seta and 3 spines of normal length and stoutness on posterodistal corner; propodus 6.6 x as long as broad, 1.5 x as long as carpus, with 14 acute spines (or pairs of spines in which one is acute) anteriorly, each spine with an accessory branch (except those of distal pair); dactylus normally developed, curved, with long unguis, about 0.32 x as long as propodus.

Pereopod 7: coxa rounded, shorter than coxa 6, slightly broader than long, 0.5 x as long as basis; basis longer than basis of pereopod 6, expanded posteriorly, 1.4 x as long as broad, with 9 short spines or groups of spines (and some submarginal spines) anteriorly, 18 very weak crenellations posteriorly, posteroventral lobe low and broadly rounded; ischium with 5 anterior groups of 1 to 5 short spines, without long setae; merus weakly expanded, 2.6 x as long as broad, anterior margin straight, posterior margin weakly convex, bearing 6 groups of 1–2 small spines of normal stoutness; carpus 2.6 x as long as broad, with spines unusually strong and numerous, with 3 spines of normal length and stoutness on posterodistal corner and two other spines on the posterior margin; propodus 5.8 x as long as broad, 1.6 x as long as carpus, with 11 acute spines (or pairs or triplets of acute spines) anteriorly, each spine with an accessory branch (except those of distal pair); dactylus normally developed, curved, with long unguis, about 0.34 x as long as propodus.

Epimeron 1: anteroventral corner subquadrate, slightly produced; posteroventral corner regularly rounded; ventral margin very slightly concave; posterior margin strongly convex.

Epimeron 2: anteroventral corner rounded, posteroventral corner acutely quadrate; ventral margin very slightly concave; posterior margin straight.

Epimeron 3: posteroventral corner regularly rounded; ventral and posterior margins slightly convex.

Urosomite 1 with a deep dorsal depression flanked on each side by lateral carina and followed by a prominent dorsal hump which is bluntly angular posteriorly.

Uropod 1: peduncle 1.6 x as long as inner ramus, with 10 very small stout lateral spines and 33 medial medium-sized slender spines; outer ramus slightly shorter than inner ramus, with 13 small lateral spines and 1 small medial spine; inner ramus with 5 medium-sized lateral spines and 15 well-developed medial spines.

Uropod 2: peduncle 1.2 x as long as inner ramus, with 7 very small stout lateral spines and 10 medium-sized narrow spines (all spines on distal 0.4); outer ramus 0.9 x as long as inner ramus, with 15 stout and medium-sized lateral spines and no medial spines; inner ramus without notch, with 8 lateral spines and 19 medial spines, all medium-sized.

Uropod 3: peduncle ordinary, about 0.80 x as long as outer ramus; outer ramus with article 1 with 10 lateral spines, 17 medial long plumose setae and 1 normally developed distomedial spine, with article 2 about 0.15 x as long as article 1; inner ramus reaching about 0.85 of article 1 of outer ramus, with 6 lateral spines and long plumose setae all along medial margin.

Telson : elongate, cleft for 0.60 of its length, each lobe with 1 apical spine paired with 1 small seta, and 4 dorsolateral spines which are all in a row.

Variations in type material. The propodus of pereopod 7 was sometimes devoid of posterior spines in paratypes (from the Falkland Islands) smaller in body size than the holotype.

Colour pattern. unknown.

Size. Up to 31 mm.

Distribution and depth range. Falkland Islands, Burdwood Bank (present material), Îles Kerguelen ( De Broyer 1983, as P. coatsi ), 55– 470 m.

Biology. This species is at least a facultative scavenger, as it enters baited traps in large swarms.

Remarks. The specimens of Pseudorchomene coatsi from Îles Kerguelen illustrated by De Broyer (1983) are identified as P. debroyeri sp. n. based on their morphological similarity. However, this would require genetic confirmation, by comparing DNA sequences with the type specimens from the distant Magellan region.

Figures

FIGURE 10. Pseudorchomene debroyeri sp. n., female, 31 mm habitus, ICEFISH cruise, Falkland Islands, S of Beauchene Island, station 14.

FIGURE 11. Pseudorchomene debroyeri sp. n., female holotype, 31 mm, ICEFISH cruise, Falkland Islands, S of Beauchene Island, station 14. A, head with appendages; B, left A 1 in medial view; C, upper lip and epistome in frontal view; D, lower lip; E, left Md; F, tip of left Md; G, tip of lacinia mobilis; H, right Md; I, tip of right Md; J, left Mx 1; K, tip of outer plate of left Mx 1 in medial view; L, right Mx 2; M, tip of right Mx 2.

FIGURE 12. Pseudorchomene debroyeri sp. n., female holotype, 31 mm, ICEFISH cruise, Falkland Islands, S of Beauchene Island, station 14. A, Mxp; B, distal half of right outer plate; C, tip of left inner plate.

FIGURE 13. Pseudorchomene debroyeri sp. n., female holotype, 31 mm, ICEFISH cruise, Falkland Islands, S of Beauchene Island, station 14. A, right Gn 1; B, left Gn 2; C, left P 3; D, left P 4; E, right P 5; F, left P 6 (drawing inverted); G, right P 7.

FIGURE 14. Pseudorchomene debroyeri sp. n., female holotype, 31 mm, ICEFISH cruise, Falkland Islands, S of Beauchene Island, station 14. A, tip of chela of right Gn 1; B, tip of chela of right Gn 2; C, propodus and dactylus of left P 3; D, distal spines of propodus of left P 3; E, distal half of right P 5; F, antepenultimate pair of spines of propodus of right P 5; G, distal half of left P 6 (drawing inverted); H, antepenultimate and penultimate pairs of spines of propodus of left P 6; I, distal half of right P 7; J, distal pairs of spines of propodus of right P 7; K, carpus of left P 7.

FIGURE 15. Pseudorchomene debroyeri sp. n., female holotype, 31 mm, ICEFISH cruise, Falkland Islands, S of Beauchene Island, station 14. A, pleon; B, right U 1; C, left U 2; D, left U 3; E, telson.

FIGURE 16. Pseudorchomene debroyeri sp. n., female, 23 mm, Kerguelen, Narres, sta. KER 82 – N 6. A, right Gn 1; B, tip of chela of right Gn 1; C, right Gn 2; D, propodus and dactylus of left P 3; E, distal spines of propodus of left P 3; F, coxa 5; G, distal half of left P 7; H, distal spines of propodus of left P 7.