Epimeria (Laevepimeria) walkeri d'Acoz & Verheye 2017, subgen. nov.

Epimeria (Laevepimeria) walkeri subgen. nov. (K.H. Barnard, 1930)

Figs 241–249

Epimeriella walkeri K.H. Barnard, 1930: 380–381, fig. 44.

Epimeriella walkeri – McCain, 1971: 160, fig. 1.

Epimeria walkeri – Coleman 2007: 60, fig. 35a–b, plate 3 fig. a, map 16 (circles, in part). — Rauschert & Arntz 2015: 62, pl. 55 unnumbered photograph.

‘ Clade C walkeri complex - WA1’ – Verheye et al. 2016a, supplement: 3 (online).

non Epimeriella walkeri subgen. nov. K.H. Barnard, 1930: 380–381, fig. 44.

Material examined

RV Polarstern cruises:

SOUTHERN OCEAN: 1 spec., cruise PS39, ANT-XIII/3, EASIZ I, stn 8, AGT 2, eastern Weddell Sea, 71°18.70ʹ S, 12°17.10ʹ W to 71°18.45ʹ S, 12°16.30ʹ W, 170–174 m, 9 Feb. 1996, coll. C. De Broyer and G. Chapelle (RBINS, INV. 132683); 1 spec., alcohol-fixed, cruise PS69, ANT-XXIII/8, stn 603-5, eastern Weddell Sea, 70°30.99ʹ S, 08°48.08ʹ W to 70°30.40ʹ S, 08°48.13ʹ W, 274–297 m, sponge bottom, Agassiz trawl, 7 Dec. 2006, coll. C. d’Udekem d’Acoz and H. Robert (RBINS, INV. 122485); 4 specs, cruise PS69, ANT-XXIII/8, stn 614-3/4/5, Elephant Island, 60°52.37ʹ S, 55°29.80ʹ W to 60°52.71ʹ S, 55°27.83ʹ W, 248–265 m, a lot of epifauna, Rauschert dredge and Agassiz trawl, 22 Dec. 2006, coll. C. d’Udekem d’Acoz and H. Robert (RBINS, INV. 122516); 1 spec., cruise PS71, ANT-XXIV/2, ANDEEP-SYSTCO, stn 48-1, eastern Weddell Sea, 70°23.94ʹ S, 8°19.14ʹ W to 70°23.89ʹ S, 8°18.67ʹ W, 595–602 m, bryozoan bottom (exceptional diversity of bryozoans), Agassiz trawl, 12 Jan. 2008, coll. H. Robert (RBINS, INV. 132448); 1 spec., cruise PS77, ANT-XXVII/3, CAMBIO, stn 222-5, southwest of King George Island, 62°17.60ʹ S, 58°41.19ʹ W to 62°17.49ʹ S, 58°41.46ʹ W, 445–889 m, Agassiz trawl, 23 Feb. 2011, coll. C. Havermans and H. Robert (RBINS, INV. 132667) [extraction A6; Genbank nr, COI: KU870819, 28S: KU759591]; 1 spec., specimen missing, DNA extraction products only, PS77, ANT-XXVII/3, CAMBIO, stn 288-3, Eastern Weddell Sea, 70°56.40ʹ S, 10°32.60ʹ W to 70°56.42ʹ S, 10°32.25ʹW, 303–311 m, Rauschert Dredge, 30 Mar. 2011, coll. C. Havermans and H. Robert [extraction Ex169; Genbank nr, COI: KU870836, 28S: KU759610]; ♂, cruise PS81, ANT-XXIX/3, stn 217-7, Bransfield Strait, 62°53.64ʹ S, 58°12.52ʹ W to 62°53.64ʹ S, 58°12.37ʹ W, 387–395 m, heterogeneous bottom (black muddy sand and gravel; small stones with incrusting bryozoans; gorgonians; sea urchins), Rauschert dredge, 2 Mar. 2013, coll. C. d’Udekem d’Acoz and M. Verheye (RBINS, INV. 122944) [extraction ANT 42; Genbank nr, COI: KU870828, 28S: KU759601].

RV Aurora Australis cruises:

SOUTHERN OCEAN: 1 spec., cruise CEAMARC, sample CEAMARC 631, stn 4EV112, Adélie Coast, 66°20ʹ16″ S, 141°59ʹ17″ E, 237–257 m, beam trawl, 26 Dec. 2007, coll. IPEV-AAD-MNHN (MNHN- IU-2014-4324); 1 spec., cruise CEAMARC, sample CEAMARC 1643, Adélie Coast, 66°34ʹ30″ S, 145°01ʹ15″ E, 429–451 m, beam trawl, 3 Jan. 2008, coll. IPEV-AAD-MNHN (MNHN-IU-2014-4323);

4 specs, cruise CEAMARC, sample CEAMARC 3532, Adélie Coast, 65°29ʹ29″ S, 139°18ʹ37″ E, 397– 411 m, beam trawl, 17 Jan. 2008, coll. IPEV-AAD-MNHN (MNHN-IU-2014-4352).

Description

HEAD + ROSTRUM. Very curved in lateral view.

ROSTRUM. In lateral view short and broad, reaching mid of article 1 of peduncle of antenna 1, anteriorly weakly curved, ventrally straight, acute-tipped; in frontal view narrow and with straight converging borders, with tip acute.

EYES. Huge, broadly elliptic, largely oriented forward (interocular distance about 1.3 × as wide as eye size when seen in frontal view).

PEREION–PLEOSOME TOOTH PATTERN. Pereionites 1–7 and pleonites 1–2 totally smooth; pleonite 3 with posterior bump.

COXAE 1–3. Tip blunt.

COXA 4. Broad, anterodorsal border nearly straight (inconspicuously concave); anteroventral border weakly convex, these two borders being joined by broad rounded convexity, which is distinctly projecting forward; anterodorsal border 1.12 × as long as anteroventral border; posteroventral border nearly straight (inconspicuously sinuate).

COXA 5. Very broad, posteroventral corner very broadly rounded in lateral view, very obtusely rounded in dorsal view (almost not projecting laterally).

COXA 6. Posterior border weakly convex; posteroventral corner very broadly rounded.

COXA 7. Posterior border nearly straight (inconspicuously concave); posteroventral corner broadly rounded.

EPIMERAL PLATES 1–3. Posteroventral angle very obtusely rounded in plate 1 (without any trace of tooth), produced into a small tooth in plates 2–3.

UROSOME TOOTH PATTERN. Urosomite 1 with distinct asymmetrical dorsal process, anteriorly nearly straight, apically blunt, posteriorly moderately convex; urosomite 3 with dorsolateral borders nearly straight (very weakly convex), with tip bluntly angulate.

TELSON. Cleft on 0.15; lobes laterally very convex, medially nearly straight, with tips blunt; notch with borders weakly convergent and end rounded.

GNATHOPODS 1–2. Carpus and propodus short and very broad; propodus not expanding distally, palm very reduced (dactylus 4 × as long as palm; gnathopods achelate or nearly so).

PEREIOPOD 4. Merus, carpus and propodus long and slender, dactylus short.

PEREIOPOD 5. Basis of normal width, with posteroproximal process absent, with posterodistal corner forming a blunt squared angle (slightly projecting posteriorly); carpus and propodus long and slender, dactylus short.

PEREIOPOD 6. Basis of normal width, with posteroproximal process absent, with posterodistal corner forming a sharp squared angle; carpus and propodus long and slender, dactylus short.

PEREIOPOD 7. Basis broad; posterior border weakly convex and slightly diverging in proximal 0.8, at this level the curvature slightly and gradually increases and becomes convergent with the anterior border; just before tip the curve becomes slightly concave; the posterior border of the basis is terminated into a small, sharp tooth (forming a small squared angle); merus very broad and short, carpus of medium width and short, propodus slender and short, dactylus short.

Colour pattern

Background whitish or very pale greyish; pereionites 3–7 yellowish/brownish; indistinct pale orange marks present here and there; peduncle of antenna 1 tinged with pale orange; urosome (especially urosomite 1) and tailfan tinged with orange; a proximal orange mark on the basis of pereiopod 7; eyes red.

Body length

Up to 30 mm.

Distribution

Type locality: Ross Sea, McMurdo Sound, 256–379 m (K.H. Barnard 1930). Other records: King George Island and Bransfield Strait, eastern shelf of the Weddell Sea, Adélie Coast; 170– 889 m.

Biology

Dauby et al. (2001a) provide some information on the gut content of Epimeria walkeri (as Epimeriella walkeri). According to them, the commonest items were ophiuroids (ossicles and parts of arms), striated muscle and diatoms. Less prevalent were sponge spicules and cnidocysts, while crustacean pieces and holothurian ossicles were infrequent. Dauby et al. (2001b) concluded that it is a macropredator/ scavenger.

Remarks

The illustrations of E. walkeri given by K.H. Barnard (1930) are difficult to understand. On his figures, the rostrum appears as broader than in specimens examined by us, but this might be related the orientation of the specimen. On the other hand, the shapes of coxa 4 and of the basis of pereiopods 5–7 are similar to that of our specimens. Our identification is only tentative. A comparison between topotypical E. walkeri (from the Ross Sea) and specimens from other Antarctic seas should be carried out whenever possible.

The collection details of the specimen illustrated by Coleman (2007: 60, fig. 35a–b) are: 72°27.7ʹ S, 17°42.32ʹ W (eastern shelf of the Weddell Sea), 240–254 m, Agassiz trawl, leg. Wägele, 15 Feb. 1985 (Coleman pers. com.). The station of the specimen illustrated by Rauschert & Arntz (2015) was indicated in an early draft made available to the authors. It is ANT-XVII/3, stn 85 [85-1], of which the coordinates are: 71°11.30ʹ S, 12°15.40ʹ W to 71°12.19ʹ S, 12°19.01ʹ W (eastern shelf of the Weddell Sea), 309– 318 m.