Epimeria (Subepimeria) teres, d’Acoz & Verheye, 2017

d’Acoz, Cédric d’Udekem & Verheye, Marie L., 2017, Epimeria of the Southern Ocean with notes on their relatives (Crustacea, Amphipoda, Eusiroidea), European Journal of Taxonomy 359, pp. 1-553 : 149-151

Epimeria (Subepimeria) teres sp. nov.

urn:lsid:zoobank.org:act:87DB1EDA-29A4-493E-84BF-9A68EFF422ED

Figs 307–313

Epimeria aff. puncticulata –? Rauschert & Arntz 2015: 61, pl. 54.

‘Clade B puncticulata complex - PUN2ʹ – Verheye et al. 2016a, supplement: 3 (online).

Epimeria puncticulata K.H. Barnard, 1930: 377 , fig. 42.

Etymology

Teres, teres , terete, Latin adjective meaning round and smooth, which seems appropriate for a very smooth Epimeria species.

Type material

Holotype

RV Polarstern cruises:

SOUTHERN OCEAN: adult, sex undetermined, cruise PS77, ANT-XXVII/3, CAMBIO, stn 248- 2, Larsen B, 65°57.51ʹ S, 60°28.15ʹ W to 65°57.69ʹ S, 60°28.30ʹ W, 196–202 m, Agassiz trawl and Rauschert dredge, 7 Mar. 2011, coll. C. Havermans and H. Robert ( RBINS, INV. 132951 ) [extraction I2; Genbank nr, COI: KU870845 , 28S: KU759622 ].

Paratype

RV Polarstern cruises:

SOUTHERN OCEAN: 1 juv., sex undetermined, cruise PS77, ANT-XXVII/3, CAMBIO, stn 248- 2, Larsen B, 65°57.51ʹ S, 60°28.15ʹ W to 65°57.69ʹ S, 60°28.30ʹ W, 196–202 m, Agassiz trawl and Rauschert dredge, 7 Mar. 2011, coll. C. Havermans and H. Robert ( RBINS, INV. 122896).

Description

ROSTRUM. In lateral view fairly short and narrow, reaching tip of article 1 of peduncle of antenna 1, weakly and regularly curved on anterior border, posterior border straight, tip very acute; in frontal view triangular: narrow, with straight converging borders, with tip blunt.

EYES. Large, broadly elliptic.

PEREION–PLEOSOME TOOTH PATTERN. Pereionites 1–7 totally smooth; pleonite 1 keeled along all its length, posteriorly terminated by tiny but distinct bump; pleonite 2 keeled with well developed acute posterodorsal tooth; pleonite 3 keeled with posterodorsal tip forming a distinct blunt process (shape: acute angle) distinctly projecting backwards.

COXAE 1–3. Tip acute.

COXA 4. Narrow; anterodorsal and anteroventral border forming a continuous curve without any trace of discontinuity (there is no distinct anterior corner), not curving significantly more ventrally; the coxa is not projecting forward; ventral corner forming an acute (nearly squared) angle of which the tip is blunt but not broadly rounded; posteroventral border distinctly concave; posterodorsal border 0.9 × as long as posteroventral border.

COXA 5. Very broad, posteroventral corner forming a blunt but distinct obtuse (nearly squared) angle.

COXA 6. Posterior border regularly rounded.

COXA 7. Posterior border straight; posteroventral corner forming a distinct obtuse angle.

EPIMERAL PLATES 1–3. Posteroventral angle: forming a squared angle in plate 1, produced into a tiny tooth in plate 2, produced into a small tooth in plate 3.

UROSOME TOOTH PATTERN. Urosomite 1 with distinct triangular dorsal process, anteriorly weakly concave, tip straight, posterior border nearly straight (inconspicuously concave); urosomite 3 with dorsolateral borders straight, with tip forming a squared angle.

TELSON. Cleft on 0.20; lobes with tips broad; notch broadly V-shaped.

GNATHOPODS 1–2. Carpus and propodus of normal slenderness; propodus not narrowing distally, and palm distinct but weak.

PEREIOPOD 5. Basis of normal width, with posteroproximal process reduced to low proximal dilatation in continuity with the more distal part of the posterior border, with posterodistal corner forming a long, narrowly triangular tooth projecting backwards; merus, carpus and propodus stout.

PEREIOPOD 6. Basis of normal width, with posteroproximal process reduced to low proximal dilatation in continuity with the more distal part of the posterior border, with posterior border distinctly diverging from anterior border, with posterodistal corner forming a triangular process (acute, nearly squared angle) weakly projecting backwards; merus, carpus and propodus stout.

PEREIOPOD 7. Basis broad; posterior border nearly straight, with weak but distinct concavity in distal 0.8, terminated into a tooth forming a squared angle.

Body length

Up to 16 mm.

Distribution

Western Weddell Sea: Larsen B, 196–202 m; probably eastern shelf of the Weddell Sea, 268–277 m (see remarks).

Remarks

Epimeria (Subepimeria) teres sp. nov. is morphologically very similar to E. (S.) urvillei sp. nov., while genetic data (COI, 28S) Verheye et al. (2016a) suggests that they are different species ( Fig. 342 ). In E. (S.) teres sp. nov., the rostrum is a bit longer, the eyes slightly more rounded, coxa 4 a bit narrower, and the tip of the basis of pereiopod 7 more produced than in E. (S.) urvillei sp. nov. It is likely that the ‘ Epimeria aff. puncticulata ’ illustrated by Rauschert & Arntz (2015) is E. (S.) teres sp. nov., as it has a narrow coxa 4, a very strong posterodorsal protrusion on pleonite 3, a very strong dorsal protrusion on urosomite 1 and a posterodistal tooth on the basis of pereiopod 7. Rauschert & Arntz (2015) did not give the collection details of their specimen, but this information was present in an early draft of their book made available to the authors. It is indicated that the specimen was collected during the cruise ANT-XXI (obviously ANT-XXI/2) at station 276 (i.e., 276-1 as there are no other sub-stations). The coordinates of this station are: 71°06.44ʹ S, 11°27.76ʹ W to 71°06.64ʹ S, 11°27.28ʹ W [eastern shelf of the Weddell Sea], 268– 277 m.

Figures

Fig. 307. Epimeria (Subepimeria) teres sp. nov., sex undetermined, holotype, Larsen B, ANT-XXVII/3, stn 248-2, RBINS, INV. 132951. A. Anterior half of body in lateral view. B. Anterior part of body in dorsal view.

Fig. 308. Epimeria (Subepimeria) teres sp. nov., sex undetermined, holotype, Larsen B, ANT-XXVII/3, stn 248-2, RBINS, INV. 132951. A. Facial habitus. B. Head in facial view.

Fig. 309. Epimeria (Subepimeria) teres sp. nov., sex undetermined, holotype, Larsen B, ANT-XXVII/3, stn 248-2, RBINS, INV. 132951. A. Pleonites 1–2, fragments (left arrow: middle of posterior border of pleonite 1, which is longitudinally split in two; right arrow: putative posterodorsal tooth of pleonite 2). B. Epimera 1. C. Epimera 2. D. Pleonite 3 and urosome.

Fig. 310. Epimeria (Subepimeria) teres sp. nov., sex undetermined, holotype, Larsen B, ANT-XXVII/3, stn 248-2, RBINS, INV. 132951. A. Head and body segments 1–3 in lateral view (antenna 1 removed on one side to make the rostrum visible). B. Head in lateral view with antenna 1 before removal. C. Urosome in dorsal view.

Fig. 311. Epimeria (Subepimeria) teres sp. nov., sex undetermined, holotype, western Weddell Sea, Larsen B, ANT-XXVII/3, stn 248-2, RBINS, INV. 132951. A. Gnathopod 1. B. Gnathopod 2. C. Pereiopod 3 or 4.

Fig. 312. Epimeria (Subepimeria) teres sp. nov., sex undetermined, holotype, Larsen B, ANT-XXVII/3, stn 248-2, RBINS, INV. 132951. A. Right pereiopod 5. B. Left pereiopod 6. C. Right pereiopod 7. D. Left pereiopod 7.

Fig. 313. Epimeria (Subepimeria) teres sp. nov., sex undetermined, juvenile paratype, Larsen B, ANT- XXVII/3, stn 248-2, RBINS, INV. 122896. A. Anterior part. B. Posterior part.

Fig. 342. Phylogenetic tree obtained by Bayesian analysis of the concatenated COI and 28S sequences, updated from Verheye et al. (2016). Bayesian posterior probabilities and bootstrap values (from the Maximum Likelihood analysis) are indicated above the nodes of interest. Bootstrap values inferior to 50 are not indicated. Besides the species names are indicated the MOTUs codes used in Verheye et al. (2016). The Genbank accession number of the outgroup species: Gnathiphimedia sexdentata (Schellenberg, 1926) are KU870835 (COI) and KU759609 (28S).