Abyssorchomene patriciae Hendrycks & Broyer 2022, sp. nov.

Abyssorchomene patriciae sp. nov.

urn:lsid:zoobank.org:act: 267EAAEE-5F5C-4DAA-93F9-014B36F6B0AB

Figs 10–17

non Abyssorchomene abyssorum – Thurston 1990: 262–263, 269 (= A. patriciae in part; part = A. cf. patriciae; T. Horton, pers. com.). —? Jones et al. 1998: 1124–1125. — Gutteridge 2012: 5, 22, 24 (= A. patriciae; T. Horton, pers. com.). — Corrigan et al. 2013: 156, 158–161 (= A. cf. patriciae). — Duffy et al. 2013: 360–368 (= A. patriciae; T. Horton, pers. com.). — Horton et al. 2013: 352, 354–358 (= A. patriciae; T. Horton, pers. com.). — Priede et al. 2013: 8 (= A. cf. patriciae). — Horton et al. 2020: 6–7, 11 (= A. patriciae; T. Horton, pers. com.).

Diagnosis

Pereonites 1–7 and pleonites 1–2 with a slight but distinct dorsoposterior hump on each segment.

Lateral cephalic lobe broadly rounded, dorsal and ventral margins slightly dissimilar in shape, dorsal margin strongly convex, ventral margin nearly straight with a very slight concavity. Antennae 1–2 of male with calceoli, female without. Epistome level with and scarcely differentiated from upper lip. Maxilla 1 palp distal end weakly convex and with conical apical spines contiguous. Maxilliped inner plate, distal margin shallowly but distinctly concave, with a very weak mediodistal extension; outer plate inner margin very weakly scalloped. Coxa 1 distinctly widened, distal width 1.3× proximal width or greater. Gnathopod 2 propodus of female broadened, subovate, length 1.7× width (different in form to narrow male propodus), dactylus large, inserted at the top of distal margin and occupying most of the length (~ 85%) of the distal margin, forming a distinct, small gap on the palm. Coxa 5 posteroventral lobe narrowly rounded, posterior margin with distinct straight section. Pereopod 7 basis, posteroventral corner shallowly and weakly beveled. Uropod 1 peduncle relatively short, length less than 1.5 × length of outer ramus. Uropod 3 inner ramus extends to ~ 63% of article 2 of uropod 3 outer ramus. Telson cleft ~ 52% of length.

Etymology

The species name is dedicated to Patricia De Broyer, the daughter of the co-author.

Material examined

Holotype NORTHEAST ATLANTIC • ♀ (mature, 10.5 mm, figured, appendages on 3 slides); Porcupine Abyssal Plain; RRS James Cook (2011), station JC 062-063; 49°05.3′ N, 16°40.0′ W; depth 4848 m; gear, baited traps, A-trap B2; 8 Aug. 2011; NHM UK 2022.6 (see Horton et al. 2020).

Allotype NORTHEAST ATLANTIC • 1 ♂ (7.5 mm, figured, appendages on 3 slides); same collection data as for holotype; NHM UK 2022.7.

Paratypes NORTHEAST ATLANTIC • 3 ♀♀ (7.0– 10.8 mm), 2 ♂♂ (5.5–7.0 mm); same collection data as for holotype; NHM UK 2022.8 • 3 ♀♀, 2 ♂♂; same collection data as for holotype; CMNC 2022-0002 • 3 ♀♀, 3 ♂♂; same collection data as for holotype; RBINS INV. 138.487.

Additional material

NORTHEAST ATLANTIC • 10 specs (♀♀ & ♂♂); same collection data as for holotype; NHM UK 2022.9 • 20 specs (♀♀ & ♂♂); same collection data as for holotype; CMNC 2022-0003 • 20 specs (♀♀ & ♂♂); same collection data as for holotype; RBINS INV. 138.488.

NORTHWEST ATLANTIC • 2 ♀♀ (7.5–8.5 mm); Mid-Atlantic Ridge area, north of Charlie-Gibbs Fracture Zone; RRS James Cook (2009), station JC 037-060; 53°58.46′ N, 36°06.12′ W; depth 2340 m; gear baited traps; 27–30 Aug. 2009; CMNC 2022-0004 • 3 ♀♀; same collection data as for preceding; RBINS INV. 138.489.

Description

Holotype

Mature female, 10.5 mm, NHM UK 2022.6.

PEREONITES 1–7 AND PLEONITES 1–2 (Figs 10–11). With a slight but distinct dorsoposterior hump on each segment (note: Fig. 10 is of male, but female is similar).

PLEONITE 3 (Fig. 11). With a rounded, posterodorsal elevation slightly overhanging urosomite 1.

COXAE 1–2 (Fig. 10). Slightly shorter than corresponding pereonites (in lateral view) (note: Fig. 10 is of male, but female is similar).

COXAE 3–4 (Fig. 10). Slightly longer (~1.2×) than corresponding pereonites (note: Fig. 10 is of male, but female coxae are slightly deeper).

EPIMERON 3 (Fig. 11). Subquadrate, with posterodistal angle very slightly obtuse, posterior margin weakly but regularly convex, ventral margin convex.

UROSOMITE 1 (Fig. 11). With a deep, narrow dorsal concavity in front of the strongly projecting, slightly unequally rounded, dorsal boss, slightly overhanging urosomite 2.

HEAD (Fig. 11). Slightly longer (1.13×) than pereonite 1.

LATERAL CEPHALIC LOBE (Fig. 11). Broadly rounded, dorsal and ventral margin not similar in shape, dorsal margin strongly convex, ventral margin nearly straight with a slight concavity.

EYE (Fig. 11). Non ommatidial, formed of pigment granules; long, narrow, L-shaped, extending parallel to the front head margin, length about 63% of the head height (note: eye shape and size are best observed with fresh specimens, as over time in preservation the labile components of the eye pigments can be lost, causing the eyes to become extremely difficult to ascertain- see eye of freshly collected male, Fig. 10).

ANTENNA 1 (Fig. 11). Peduncular article 1 dilated (length 1.3× width), without small dorsal keel projecting distally over article 2; flagellum broken after the sixth article (likely with 9–10 articles counted from 6 other females), length 1.5 × peduncle, first article of flagellum callynophorate, densely furnished medially with double row of aesthetascs; accessory flagellum 5-articulate, first article slightly broader and longer than remaining articles combined, calceoli absent.

ANTENNA 2. Slightly longer (less than 1.3×) than antenna 1; geniculate between peduncular articles 3–4, peduncular articles 4–5 lined with anteromedial brush setae; flagellum 12-articulate, calceoli absent.

EPISTOME (Fig. 11). Level with and scarcely differentiated from upper lip, forming long anterior cephalic ridge, weakly concave.

UPPER LIP (Fig. 12). Not protruding, with an asymmetrical midventral, angular projection.

MANDIBLE (Fig. 12). Incisor strongly convex and widened; left lacinia mobilis curved, with 2 strong apical teeth, right lacking; accessory spine row with 3 strong spines, interspersed with fine setae; molar forming a narrow crest, somewhat falciform, acutely produced on proximal end, setose with mixed ornamentation, distal half or third setiferous, proximal half or two-thirds forming a reduced, ridged triturative surface, hairy process attached proximal to molar; palp attached proximal to molar, article 2 1.65 × length of article 3, with 17 A2 setae, article 3 falciform, 0.61× length of article 2, with 1 A3-seta, 20 D3-pectinate setae and 3 E3-setae.

LOWER LIP. Outer lobes broad with inner margins strongly setose, distal inner margins excavated; without inner lobes, mandibular lobes narrow, rounded.

MAXILLA 1 (Fig. 12). Inner plate with small, distal subtriangular projection surpassing the basal insertion of the 2 subapical plumose setae; outer plate with 11 elongated spine-teeth in 7/4 crown arrangement; palp article 2 strongly widened at distal two-thirds, with 10 (left side) or 9 (right side) contiguous conical apical spines, and one apical strong seta on outer corner.

MAXILLA 2 (Fig. 13). Outer and inner plates tapering distally, both with strong rows of pectinate medial marginal spines and setae; inner plate much shorter and distinctly narrower than outer plate, with marginal setae on the distal third of the inner margin, distal end of inner plate not reaching the proximal end of setal row of outer plate.

MAXILLIPED (Fig. 13). Inner plate subrectangular, extending slightly past the distal end of the inner margin of palp article 1 and reaching about 0.34 × length of outer plate, distal margin shallowly but distinctly concave, with very weak mediodistal extension, not surpassing the level of the weak outer extension, with 3 strongly embedded nodular spines, the two mediodistal marginal nodular spines situated close to each other, the third one located in about the middle of the plate, medial margin strongly setose; outer plate elongated, subovate, length 1.83× width, reaching the distal end of palp article 2, with two dissimilar apical spines and numerous (12) embedded, medial nodular spines, medial margin very slightly scalloped; palp strongly setose medially, article 4 well developed, about 0.56 × length of article 3, inner margin with 2–3 distal setae.

GNATHOPOD 1 (Fig. 14). Coxa distinctly widened, distal width 1.3× proximal width and about 76% of length, anterior margin concave, anterodorsal corner rounded, posterior margin nearly straight, distal margin strongly convex in anterior half, weakly convex in posterior half, posteroventral corner not narrowly rounded; basis stout, width about one third of the length and similar to propod width, anterior margin with very short setae; ischium subequal to merus, both with posterior margins setose; carpus short, about half the length of the propodus, with produced narrow posterodistal lobe, not guarding the hind margin of propodus; propodus subchelate, subrectangular, slightly narrowing distally, with anterior margin regularly convex, posterior margin slightly concave, with a distinct inflexion at distal two-thirds, palm transverse, microcrenulate, palmar corner with 2 blunt protrusions and defined by 1 medial and 1 lateral spine; dactylus subequal to palm or barely overriding palm corner.

GNATHOPOD 2 (Fig. 15). Coxa subrectangular, length 2.2 × width; basis elongated, distal third slightly curved, length 7.3× width; ischium length 2.7 × width; carpus stout, length 2 × width, about 1.6 × propodus; propodus chelate, subovate, length 1.72 × width, widest subproximally and about 75% of the carpus width, surface finely setose with distal groups of long pectinate setae, dorsal margin strongly convex, hind margin weakly convex, nearly straight; dactylus large, inserted at the top of the distal margin and occupying most of the length (~ 85%) of the distal margin, forming a distinct, small gap on the palm.

PEREOPOD 3 (Fig. 16). Coxa with anterior margin very slightly convex, posterior margin nearly straight, length 2.3× width; posterior margins of ischium-merus with clusters of long setae; rest of pereopod as in pereopod 4.

PEREOPOD 4 (Fig. 16). Coxa length 1.4 × width, width 0.7 × length, anterior margin strongly convex, posterior margin deeply excavate, with wide subtriangular, posterodistal lobe, ventral margin straight, angle subrectangular with rounded apex, located at distal 70% of the coxa length; posterior margins of ischium-merus with clusters of long setae; propodus with 4–5 short spine groups; dactylus 0.43× length of propodus.

PEREOPOD 5 (Fig. 16). Coxa slightly but distinctly posterolobate, posterior lobe narrowly rounded, irregularly convex, with distal half of posterior margin straight, width slightly exceeding (1.12 ×) length; basis slightly longer (1.1 ×) than wide, regularly narrowing distally from halfway along the posterior margin, with 4 weak serrations, posterodistal lobe extending to distal margin of ischium; merus weakly expanded (width 0.66 × length), longer than carpus and bearing anterior and posterior long setae; carpus with anterior marginal setae; propodus narrow, length equal to merus-carpus, with 4–5 anterior marginal short spine groups; dactylus short, length 0.34 × propodus.

PEREOPOD 6 (Fig. 16). Basis long, length 1.5× width, posterior margin with 8 weak serrations, posterodistal lobe not reaching distal margin of ischium; merus slightly expanded (slightly narrower than in P5) and bearing anterior marginal long setae and few short slender posterior spines; propodus equal in length to merus-carpus, anterior margin with 4–5 clusters of short spines; dactylus 0.33× length of propodus.

PEREOPOD 7 (Fig. 16). Coxa subovate, length slightly shorter than width; basis proximal two-thirds subrectangular, anterior margin slightly concave, distal third of posterior margin with a relatively strongly angled bevel, with about 9 weak serrations, posterodistal lobe not extending to distal margin of ischium; merus not expanded (narrower than in P6), anterior margins of merus-carpus with short spine groups, posterior margin bearing few short slender spines; propodus about equal to merus-carpus; dactylus 0.33× length of propodus.

UROPOD 1 (Fig. 17). Peduncle about 1.45 × length of outer ramus and 1.64× inner ramus, dorsolateral and dorsomedial margins spinose; inner ramus shorter and more spiniferous than outer ramus; outer ramus medial margin lacking spines.

UROPOD 2 (Fig. 17). Peduncle length 1.2× outer ramus, dorsolateral and dorsomedial margins with 5 and 1 spine respectively; inner ramus slightly shorter than outer ramus, outer ramus with 10 closely spaced slender spines on dorsolateral margin; inner ramus margins with 2 and 3 slender spines.

UROPOD 3 (Fig. 17). Peduncle 0.77 × length of biarticulate outer ramus; second article of outer ramus 0.38× length of article 1; inner ramus extends past distal end of article 1 of outer ramus and reaches 0.63× length of article 2 of outer ramus, inner margins of rami with long plumose setae and outer margins with a few slender spines.

TELSON (Fig. 17). 1.7 × longer than wide, cleft (52%), lobes tapering distally with 2–3 lateral, submarginal spines and 1 distal spine set in middle of lobe tip.

GILLS 5 AND 6 (Fig. 16). With 1 long, tubular accessory lobe on gill 5 and 2 lobes on gill 6.

GILL 7 (Fig. 16). Present, well developed.

BROOD PLATES (Figs 15–16). Present on gnathopod 2 and pereopods 3–5, long, slender and curved distally, largest on gnathopod 2 and pereopods 3–4, smallest on pereopod 5, with long curved brood setae ranging in number from 11–24.

STOMODEUM. Extending to the 7 th pereonite.

Male (Allotype 7.5 mm, NHM UK 2022.7).

Similar to female, but differing as follows:

BODY (Fig. 10). Smaller and generally less robust.

HEAD (Figs 10–11). Slightly longer (1.27×) than pereonite 1.

LATERAL HEAD LOBE (Figs 10–11). Narrower distally and dorsal margin not as strongly convex.

ANTENNA 1 (Fig. 11). Longer relative to body length than female, peduncle 1 stouter, length very slightly greater than width; callynophore stronger, flagellar articles shorter, with calceoli.

ANTENNA 2 (Fig. 11). Longer relative to body length than female, flagellum 14-articulate, with calceoli.

MANDIBLE (Fig. 12). Palp article 2 shorter, length 1.5 × article 3.

MAXILLA 1 (Fig. 12). Inner plate, distal projection more acute.

MAXILLIPED (Fig. 13). Inner plates, distal margin more deeply excavated.

PEREOPODS (Figs 14, 17). Coxae narrower; rest of pereopods slightly more gracile.

GNATHOPOD 1 (Fig. 14). Coxa slightly less widened, anteroventral corner more narrowly rounded; basis distinctly narrower than propodus.

GNATHOPOD 2 (Fig. 14). Coxa narrower and slightly widened distally; propodus distinctly narrower, length 2.48 × width and about 61% of carpus width, with straight hind margin, palm without a gap.

COXA 4 (Fig. 17). Distinctly narrower, with posterodistal lobe more regularly convex.

PEREOPOD 5 (Fig. 17). Merus more strongly expanded (width 0.7× length).

UROPOD 2 (Fig. 17). Distolateral marginal spines of peduncle grouped closely together; inner ramus distinctly shorter than outer; outer ramus distolateral spines much stouter, bluntly rounded and more closely spaced, proximal ones are slender and sharp (see comment, p. 24).

UROSOMITE 1 (Fig. 10). Boss slightly more protruding.

Distribution

Northeast and Central North Atlantic: Porcupine Abyssal Plain (Thurston 1990); Biscay Abyssal Plain? Cape Verde Basin? (Thurston 1990: identifications to be confirmed); Mid-Atlantic Ridge vicinity (Horton et al. 2013)

Depth range

Bottom records: 2340 m (Horton et al. 2013) to 4849 m (Thurston 1990).

Pelagic records: 0–20 to 500–1000 m above bottom (Thurston 1990, identifications to be confirmed).

Remarks

In many subtle ways, the new species Abyssorchomene patriciae sp. nov. appears to be a pseudocryptic species, with a facies very superficially similar to both the north and southwest Atlantic species A. abyssorum (Stebbing, 1888) and the southwest Atlantic-Antarctic new species A. shannonae sp. nov. (this paper). For instance, these three species all possess the slight, but distinct dorsoposterior rounded hump on pereonites 1–7 and pleonites 1–2, which is unique among Abyssorchomene. As well, the uropod 3 inner ramus extends past the distal end of article 1 of the outer ramus of uropod 3. These characters easily differentiate A. abyssorum, A. patriciae and A. shannonae from the Southern Ocean endemic A. scotianensis (Andres, 1983).

In general body shape and form, they are all extremely similar. However, upon critical examination, we have found several detailed morphological characters that differentiate A. patriciae sp. nov. as follows (character of A. abyssorum in brackets). From A. abyssorum, it differs in the shape of the lateral head lobe, with dorsal and ventral margins not similar, dorsal margin strongly convex, ventral margin nearly straight with slight concavity (vs dorsal and ventral margins more similar, dorsal margin weakly convex and ventral margin straighter); coxa 1 is distinctly widened distally and the anterodorsal corner is broadly rounded in the female (vs only very slightly widened and the anterodorsal corner is narrowly rounded in the female); the mature female gnathopod 2 propodus broadened, subovate, length ~ 1.7 × width, dactylus large, inserted at the top of the distal margin and occupying most of the distal margin, with a small palmar gap (vs propodus very slender, similar to male, length ~ 2.5 × width, dactylus tiny, without a palmar gap); the shorter uropod 1 peduncle, which is 1.45 × the length of the outer ramus (vs longer uropod 1 peduncle, which is 1.5–1.7 × the outer ramus) and the length of the uropod 3 inner ramus, which reaches to ~ 63% of article 2 of uropod 3 outer ramus (vs reaching to ~ 70% of article 2 of outer ramus). The broadened gnathopod 2 propodus of mature females is not found in smaller, immature females and is likely a terminal growth stage character which presents at maturity, when brood plates are fully formed with long brood setae. Immature females possess a gnathopod 2 propodus which approximates the condition found in males. These are slender and lack the palmar concavity. This makes these taxa difficult to separate without mature females; however, we give other characters which, in total, aid in identifying these species without mature females. Several of these small differences are found in the mouthparts, especially maxilla 2 and the maxilliped and these are outlined in the descriptive text for this species.

The characters that differentiate A. patriciae sp. nov. and A. shannonae sp. nov. are outlined in the Remarks section under A. shannonae (p. 67) and in the key (p. 68).