Abyssorchomene shannonae, Hendrycks & Broyer, 2022

Hendrycks, Ed A. & Broyer, Claude De, 2022, New deep-sea Atlantic and Antarctic species of Abyssorchomene De Broyer, 1984 (Amphipoda, Lysianassoidea, Uristidae) with a redescription of A. abyssorum (Stebbing, 1888), European Journal of Taxonomy 825, pp. 1-76 : 53-67

Abyssorchomene shannonae sp. nov.

urn:lsid:zoobank.org:act:EEBF5622-BB6E-4CA5-9767-4CFE71A4ED9F

Figs 26–34

Diagnosis

Pereonites 1–7 and pleonites 1–2 with a weak but distinct dorsoposterior hump on each segment. Lateral cephalic lobe broadly rounded, dorsal and ventral margins nearly equally convex. Antennae 1–2 of male with calceoli, female without. Epistome level with the upper lip. Maxilla 1 palp, distal end weakly convex with distal conical spines contiguous. Maxilliped inner plate, distal margin nearly straight, strongly beveled, with a very slight concavity on outer half, with mediodistal extension surpassing outer corner; outer plate with strongly scalloped inner margin. Coxa 1 strongly widened distally, ~ 1.5–1.7 × proximal width. Gnathopod 2 propodus of female broad, anterodistal margin slightly expanded and protruding, length ~ 1.5× width, (different in form to narrow male propod), dactylus very small, inserted on the posterodistal one-third of the distal margin, palm with a distinct concavity. Coxa 5 distinctly posterolobate, posteroventral lobe broadly rounded, posterior margin evenly rounded. Pereopod 7 basis with anterior margin slightly concave, distal half of posterior margin with a steep, strong bevel. Uropod 1 peduncle long, about 1.6× length of outer ramus. Uropod 3 inner ramus extends past distal end of article 1 and reaches 20–25% length of article 2 of outer ramus. Telson cleft 55% of length, deeper in males.

Etymology

The species name is dedicated to Shannon Hendrycks, the wife of the first author for her continued enthusiasm and support over the many years of this and other amphipod studies.

Material examined

Holotype EASTERN WEDDELL SEA • ♀ (12 mm, mature, figured, appendages on 7 slides); RV Polarstern ANT XXII-3 (ANDEEP III), station PS67-78-1; 71°9.91′ S, 014°4.80′ W; depth 2194 m; gear, baited traps; 21 Feb. 2005; C. De Broyer and B. Danis leg.; ZMH K-61209 .

Allotype EASTERN WEDDELL SEA • ♂ (7 mm, figured, appendages on 6 slides); same collection data as for holotype; ZMH K-61210 .

Paratypes EASTERN WEDDELL SEA • 2 ♀♀ (8.4 mm, with dissected Gn1–2, 9.5 mm); same collection data as for holotype; RBINS INV. 138.491 • 2 ♀♀ (8.4 mm, 11.8 mm); same collection data as for holotype; CMNC 2022-0009 • 2 ♀♀ (mature, 10 mm), 4 ♀♀ (immature, 7.5 mm), 4 ♂♂ (~ 6 mm); same collection data as for holotype; CMNC 2022-0010 .

Additional material

EASTERN WEDDELL SEA • 6 specs (6–8 mm); RV Polarstern ANT XXII-3 (ANDEEP III), station PS67-80-1; 70°40.78′ S, 014°41.24′ W; depth 2928 m; gear, baited traps; 22 Feb. 2005; C. De Broyer and B. Danis leg.; RBINS INV. 138.492 • 2 ♀♀ (immature, 8.0 mm, 9.0 mm), 2 ♂♂ (5.6 mm, 7.0 mm); RV Polarstern ANT XXII-3 (ANDEEP III), station PS67-81-1; 70°31.63′S, 014°35.00′W; depth 4412 m; gear, baited traps; 23 Feb. 2005; C. De Broyer and B. Danis; RBINS INV. 138.496 .

NORTHWEST WEDDELL SEA • 1 ♀ (12.4 mm, mature); Powell Basin ; RV Polarstern ANT XXII-3 (ANDEEP III), station PS67-142AT; 62°12.40′ S, 049°31.67′ W; depth 3411 m; gear, baited traps; 18 Mar. 2005; C. De Broyer and B. Danis leg.; RBINS INV. 138.497 .

SCOTIA SEA • 1 ♀ (12 mm, mature); US Antarctic Research Program, Eltanin 9, station 696; 56°53′ S – 56°59′ S, 037°27′ W – 037°17′ W; depth 3001 m; gear, Isaac-Kid Midwater Trawl; 28 Aug.1963; Smithsonian Oceanographic Sorting Centre, Washington, D.C .

SOUTHWEST ATLANTIC • 2 ♀♀ (7 and 8 mm, immature), 1 ♂ (6 mm); Argentine Basin; RV Meteor, DIVA 3 M79/1 expedition, station 531; 35°56.49′ S, 048°53.85′ W; depth 4586 m; gear, baited traps; 15 Jul. 2009; E. Hendrycks leg.; ZMH K-61211 .

Description

Holotype

Mature female, 12 mm, ZMH K-61209.

PEREONITES 1–7 AND PLEONITES 1–2 ( Fig. 26 ). With a slight but distinct dorsoposterior hump on each segment.

PLEONITE 3 ( Fig. 26 ). With a rounded, posterodorsal elevation slightly overhanging urosomite 1.

COXAE 1–2 ( Fig. 26 ). Slightly shorter to nearly subequal to corresponding pereonites (in lateral view).

COXAE 3–4 ( Fig. 26 ). Subequal to slightly longer (1.15 ×) than corresponding pereonites.

EPIMERON 3 ( Fig. 26 ). Subquadrate, with posterodistal angle narrowly rounded and slightly obtuse, posterior margin very weakly convex, nearly straight, ventral margin convex.

UROSOMITE 1 ( Fig. 26 ). With a deep, broadly rounded dorsal concavity in front of the strong, regularly rounded, dorsal boss, slightly overhanging urosomite 2.

LATERAL CEPHALIC LOBE ( Fig. 26 ). Broadly rounded, dorsal and ventral margin nearly equally convex.

EYE ( Fig. 26 ). Non ommatidial, formed of pigment granules; long, relatively narrow, crescent shaped; extending parallel to the front head margin, length about two-thirds of the head height.

ANTENNA 1 ( Fig. 26 ). Peduncular article 1 dilated, length 1.3 × width; flagellum 13-articulate, length 1.5× peduncle, first article of flagellum callynophorate, densely furnished with double row of aesthetascs medially; accessory flagellum 5-articulate, first article wider and longer than remaining articles combined; calceoli absent.

ANTENNA 2 ( Fig. 26 ). 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 16-articulate, calceoli absent.

EPISTOME ( Fig. 26 ). Level with the slightly rounded upper lip, from which it is separated by a minute slit; forming long anterior cephalic ridge, weakly concave upward.

UPPER LIP ( Fig. 26 ). Anterior margin weakly convex, not protruding; midventral margin with a small, angular projection.

MANDIBLE ( Fig. 29 ). Incisor smoothly convex and slightly widened; left lacinia mobilis curved, with 2 strong and 1 weak 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, narrow, triturative surface, hairy process attached proximal to molar; palp attached proximal to molar, article 2 1.56 × length of article 3, with 27 A2 setae, article 3 falciform, 0.63 × length of article 2, with 1 A3-seta, 22 D3-pectinate setae and 3 E3 setae.

LOWER LIP ( Fig. 28 ). Outer lobes broad, slightly truncated medially and strongly setose, without inner lobes, mandibular lobes narrow.

MAXILLA 1 ( Fig. 28 ). Inner plate ovate, with small blunt distal projection surpassing the basal insertion of the 2 plumose apical setae; outer plate with 11 elongated spine-teeth in 7/4 crown arrangement; palp article 2 slightly widened at distal two-thirds, with 10 (left side) or 9 (right side) contiguous (or nearly contiguous) conical apical spines.

MAXILLA 2 ( Fig. 28 ). Outer and inner plates strongly tapering distally, both with strong rows of pectinate medial marginal spines and setae; inner plate much shorter than outer plate, with marginal setae on the distal half of the inner margin; apex of inner plate slightly surpassing the proximal end of setal row of outer plate.

MAXILLIPED ( Fig. 30 ). Inner plate short, subrectangular, just reaching the distal end of the inner margin of palp article 1 and reaching about 0.3× length of outer plate, distal margin not excavate, very weakly concave on outer half and sloped, with weak medio-distal extension, with 3 equally spaced, strongly embedded nodular spines, medial margin strongly setose; outer plate well developed, subovate, length 1.58× width, not reaching inner distal end of palp article 2, with two dissimilar apical spines and numerous (10–11) embedded, medial nodular spines, medial margin distinctly scalloped; palp strongly setose medially, article 4 well developed, about half the length of article 3, with 6 apically plumose setae on distal inner margin.

GNATHOPOD 1 ( Fig. 31 ). Coxa distinctly widened, distal width 1.53 × proximal width and about 80% of length, anterior margin slightly concave, anterodorsal corner broadly rounded, posterior margin slightly sinuous, the distal half weakly concave, slightly convex in posterior half, posteroventral corner nearly right angled, narrowly rounded; basis stout, not expanded, width one-third of the length, slightly narrower than propod, anterior margin with long setae; ischium subequal to merus; carpus short, about half the length of the propodus, with produced narrow posterodistal lobe, not guarding the hind margin of propodus; propodus subchelate, subrectangular, with anterior margin regularly convex, posterior margin distinctly concave, with inflexion point at distal two-thirds, palm transverse, microcrenulate, palm 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. 31 ). Carpus stout, length 2× propodus; propodus chelate, suboval, anterodistal margin broadly expanded and slightly protruding, surface finely setose with distal groups of long pectinate setae, broad, length 1.48 × width, slightly narrower (about 90%) than carpus, hind margin weakly but distinctly convex; dactylus very small, inserted on the posterodistal one-third of distal margin, forming a distinct, curved cavity with the slightly excavate palm.

PEREOPOD 3 ( Fig. 32 ). Coxa with anterior margin slightly convex, posterior margin slightly concave, length 2.3× width; rest of pereopod like pereopod 4.

PEREOPOD 4 ( Fig. 32 ). Coxa with posterodistal lobe broadly rounded distally, angle subquadrate, located slightly more distally (55%) than half of the coxa length; posterior margins of ischium-merus with clusters of long setae; propodus with 6 short spine groups; dactylus ~ 0.4 × length of propodus.

PEREOPOD 5 ( Fig. 32 ). Coxa distinctly posterolobate, posterior lobe broad and regularly convex, coxa width slightly greater than length; basis length 1.13× width, posterior margin with small serrations and setules, posterodistal lobe extending to distal margin of ischium; merus slightly expanded (0.63× length), longer than carpus and bearing anterior and posterior setae; carpus with anterior marginal setae; propodus narrow, length equal to merus-carpus.

PEREOPOD 6 ( Fig. 32 ). Coxa with posterodistal lobe broadly rounded; basis length 1.54 × width, posterior margin with 3–4 weak serrations, posterodistal lobe not reaching distal margin of ischium; merus slightly expanded (narrower than in P5) and bearing anterior long setae and few short slender posterior spines only; propodus slightly shorter than merus-carpus, with 6–7 clusters of short spines; dactylus 0.3× length of propodus.

PEREOPOD 7 ( Fig. 32 ). Coxa small, subovate; basis with anterior margin slightly concave, distal half of posterior margin strongly beveled, nearly straight, with very weak concavity and 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 slightly shorter than merus-carpus; dactylus 0.3× length of propodus.

UROPOD 1 ( Fig. 33 ). Peduncle long, about 1.6 × length of outer ramus and 1.74 × length of inner ramus, dorsolateral and dorsomedial margins spinose; inner ramus slightly shorter than outer, margins of rami with slender spines except medial margin of outer ramus, which lacks spines.

UROPOD 2 ( Fig. 33 ). Peduncle about 1.2× length of outer ramus, dorsolateral and dorsomedial margins with 4 and 3 spines respectively; inner ramus very slightly shorter than outer ramus; outer ramus with closely spaced slender spines on dorsolateral margin; inner ramus margins with slender spines.

UROPOD 3 ( Fig. 33 ). Peduncle long, 0.8 × length of biarticulated outer ramus; second article of outer ramus 0.46 × length of article 1; inner ramus extends past distal end of article 1 and reaches 20–25% of article 2 of outer ramus; inner margins of rami with long plumose setae and slender spines.

TELSON ( Fig. 33 ). 1.6 × longer than wide, relatively deeply cleft (55%), lobes tapering distally with 4 lateral, submarginal spines and 1 distal spine.

GILLS 5–6 ( Fig. 32 ). With 1 long tubular accessory lobe on gill 5 and 2 on gill 6.

GILL 7 ( Fig. 32 ). Present, well developed.

BROOD PLATES ( Fig. 32 ). On gnathopod 2 and pereopods 3–5, long, slender and curved distally, largest on gnathopod 2 and pereopods 3–4, with long curved brood setae, 20 setae on pereopod 4 plate and 12 on pereopod 5.

STOMODEUM ( Fig. 26 ). Extending to the 7 th pereonite.

Male (Allotype 7 mm, ZMH K-61210).

Similar to female, but differing as follows:

BODY. Smaller than female, and slightly less robust.

LATERAL HEAD LOBE. Slightly narrower.

ANTENNA 1 ( Fig. 27 ). Peduncular article 1 stouter, more compact; callynophore stronger, flagellum 8-articulate, articles shorter, with calceoli.

ANTENNA 2 ( Fig. 27 ). Flagellum 12-articulate with calceoli.

MAXILLA 1 ( Fig. 28 ). Palp with 7 distal, conical spines; inner plate, distal projection acute.

MAXILLIPED ( Fig. 30 ). Inner plate, distal margin slightly more excavate.

PEREOPODS ( Fig. 34 ). Slightly more slender.

GNATHOPOD 1 ( Fig. 34 ). Coxa more strongly widened, distal width about 1.7 × proximal width; basis distinctly narrower than propodus, anterior margin lacking long setae.

GNATHOPOD 2 ( Fig. 34 ). Coxa slightly narrower and distally widening; propodus slender, length 2.5 × width, about ⅔ of carpus width, slightly expanded anteriorly, with straight hind margin, palm lacking concavity.

COXA 3 ( Fig. 34 ). Slightly narrower and widening distally.

COXA 4 ( Fig. 34 ). Slightly narrower, ventral margin more evenly convex and posteroventral lobe slightly smaller.

COXA 5. Slightly more posterolobate.

UROPOD 2 ( Fig. 33 ). Peduncle shorter, about 1.13 × length of outer ramus, distolateral marginal spines of peduncle grouped at distal end; inner ramus distinctly shorter than outer; outer ramus distolateral spines stouter, bluntly rounded and more closely spaced distally, proximal spine acute (see p. 24).

UROPOD 3 ( Fig. 33 ). Peduncle shorter, 0.68 × length of biarticulated outer ramus.

TELSON ( Fig. 33 ). Cleft deeper (60%) than female.

UROSOMITE 1 ( Fig. 26 ). Dorsal boss more unevenly rounded and slightly more protruding upward.

EPIMERON 3 ( Fig. 26 ). Posteroventral corner slightly more subquadrate.

Distribution

Southern Ocean: Eastern Weddell Sea ( De Broyer et al. 2006); Northwestern Weddell Sea: Powell Basin ( De Broyer et al. 2006); Scotia Sea (this paper). Southwest Atlantic: Argentine Abyssal Basin (this paper).

Depth range

Bottom records: 2194 m ( De Broyer et al. 2006) to 4586 m (this paper).

Pelagic records: 3001 m (this paper).

Remarks

Abyssorchomene shannonae sp. nov. is easily differentiated from the smooth bodied Antarctic species A. scotianensis ( Andres, 1983) in possessing a slight, but distinct dorsoposterior rounded hump on pereonites 1–7 and pleonites 1–2. The new species also differs from A. scotianensis by the very steeply angled, truncate bevel of the basis of pereopod 7 (vs weakly angled bevel) and the uropod 3 inner ramus length, which greatly exceeds the distal end of article 1 of the outer ramus (vs just reaching the distal end).

Abyssorchomene shannonae sp. nov. is superficially very similar to A. abyssorum and A. patriciae sp. nov., as these species also possess the dorsoposterior hump on the pereonites and pleonites. However, A. shannonae differs from both these species in many characters. From A. abyssorum , it differs in the much greater distally widened coxa 1 (1.4–1.7× proximal width vs 1.2×); the (mature) female gnathopod 2 propodus which is broad, with a palm concavity (length less than 1.5 × width vs narrow, ~ 2.4× width and lacking concavity); the coxa 5 posteroventral lobe which is broadly rounded (vs narrowly rounded); the very strongly, steeply angled truncated bevel of the basis of pereopod 7 (vs weakly angled bevel) and the shorter uropod 3 inner ramus, which extends to about 20–25% of the length of article 2 of the outer ramus (vs extends to 70% of the length of article 2 of the outer ramus).

Lastly, from A. patriciae sp. nov. it differs in the shape of the lateral head lobe, with dorsal and ventral margins nearly similar (vs dorsal and ventral margins not similar, dorsal margin strongly convex, ventral margin nearly straight); the female gnathopod 2 propodus with anterodistal margin broadly expanded and protruding, dactylus tiny, inserted near the bottom of the distal margin (vs anterodistal margin not expanded and protruding, dactylus large, inserted at the top of the distal margin); the coxa 5 posteroventral lobe which is broadly and evenly rounded (vs narrowly rounded, posterior margin straight posterodistally); the longer uropod 1 peduncle, which is 1.6 × the length of the outer ramus (vs 1.45 ×) and the length of the uropod 3 inner ramus, which reaches to 20–25% of article 2 of uropod 3 outer ramus (vs reaching to ~ 63% of article 2 of outer ramus).

Figures

Fig. 26. Abyssorchomene shannonae sp. nov., holotype, ♀, 12 mm (ZMH K-61209); allotype, ♂, 7 mm (ZMH K-61210), RV Polarstern ANT XXII-3 (ANDEEP III), station PS67-78-1, eastern Weddell Sea, depth 2194 m., 21 February 2005. Dotted line on habitus shows approximate stomodeum position. Figures with sex not indicated are of female. Scale bars = 1 mm.

Fig. 27. Abyssorchomene shannonae sp. nov., allotype, ♂, 7 mm (ZMH K-61210). Most aesthetascs omitted from A1 callynophore. Scale bars = 0.5 mm.

Fig. 28. Abyssorchomene shannonae sp. nov., holotype, ♀, 12 mm (ZMH K-61209); allotype, ♂, 7 mm (ZMH K-61210). LL partially broken. Figures with sex not indicated are of female. Scale bars = 0.1 mm.

Fig. 29. Abyssorchomene shannonae sp. nov., holotype, ♀, 12 mm (ZMH K-61209); allotype, ♂, 7 mm (ZMH K-61210). From left to right: dorsolateral, medial and frontal aspects of Md. Setae omitted on male Md palp. Figures with sex not indicated are of female. Scale bars = 0.1 mm unless indicated otherwise.

Fig. 30. Abyssorchomene shannonae sp. nov., holotype, ♀, 12 mm (ZMH K-61209); allotype, ♂, 7 mm (ZMH K-61210). Figures with sex not indicated are of female. Scale bars = 0.1 mm.

Fig. 31. Abyssorchomene shannonae sp. nov., holotype, ♀, 12 mm (ZMH K-61209). Setae omitted on Gn2 propodus outline. Scale bars = 0.1 mm unless indicated otherwise.

Fig. 32. Abyssorchomene shannonae sp. nov., holotype, ♀, 12 mm (ZMH K-61209). Scale bars = 0.5 mm.

Fig. 33. Abyssorchomene shannonae sp. nov., holotype, ♀, 12 mm (ZMH K-61209); allotype, ♂, 7 mm (ZMH K-61210). Outer ramus is oriented on the left side of the uropods. Figures with sex not indicated are of female. Scale bars = 0.1 mm.

Fig. 34. Abyssorchomene shannonae sp. nov., allotype, ♂, 7 mm (ZMH K-61210). Setae omitted on Gn1 detail and P3. Scale bars = 0.5 mm unless indicated otherwise.