Epimeria robustoides Lörz & Coleman, 2009

Loerz, Anne, Maas, Elizabeth, Linse, Katrin & Coleman, Charles Oliver, 2009, Do circum-Antarctic species exist in peracarid Amphipoda? A case study in the genus Epimeria Costa, 1851 (Crustacea, Peracarida, Epimeriidae), ZooKeys 18, pp. 91-128 : 100-106

Epimeria robustoides Lörz & Coleman , sp. n.

urn:lsid:zoobank.org:act:96CEBCCA-C3EB-4219-AC2B-C6E81BD852D1

Figs 2–5

Epimeria robusta . – Bamard, 1958: 108; 1961: 103.– McCain 1971: 161.– De Broyer and Klages 1991: 164.– Coleman 1994: 560.

Material examined. Holotype. Ovig. female 40 mm. 72°35.67´5S, 18°8.17´W, depth 604–656 m, collected during the Polarstern cruise ANT III 1985 by Agassiz-trawl, 27.I.1985, station 273.

Etymology. The species is named robustoides because of its morphological similarity to Epimeria robusta .

Diagnosis. Body ( Fig. 2A, B ) robust. Posterior margin of pereonites 5–6 with small medial protrusion, pereonite 7 with shallow keel, pereonite 7 and posterior margins of metasome segments 1–2 with an elevation (in lateral view). Metasome segments 1–3 with mid-dorsal keel, metasome segment 3 and urosomite 1 with pointed tooth. Urosomite 3 with shallow mid-dorsal keel. Coxa of pereopods 1–3 tapering distally, apically rounded ( Figs 4A, B, E ). Propodus of gnathopods 1–2 expanded distally, with well-developed palm. Coxa of pereopod 4 very large, with wide posteroventral angle projecting somewhat ventrally. Pereopod 5 ( Fig. 5D ) ba- sis with posteromarginal tooth, basis of pereopod 6 with similar tooth but larger, pereopod 7 basis ( Fig. 5C ) widened proximally, but without tooth, only posterodistal angle pointed.

Distribution. Weddell Sea, 604– 656 m.

Description. Anterior cephalic margin sinuous, lateral cephalic lobe slightly produced; rostrum same length as head, reaching proximal part of antenna 1 peduncle

article 1; eyes present, oval, 0.4 × head height. Pereonite 1 subequal in length to head (excluding rostrum), pereonite 2 approx. 0.75 x length of pereonite 1, pereonites 1 to 6 lacking mid-dorsal or dorsolateral processes; pereonite 7 posterior margin with dorsolateral carina weakly developed; pleonites 1–3 with carinae, pereonite 3 and urosomite 1 with acute mid-dorsal process. Urosomite 2 shortest, lacking mid-dorsal process, urosomite 3 with pointed posterior process.

Epimeron. 1 antero- and posteroventral angle rounded; epimeron 2 and 3 posteroventral angle produced.

Antenna. 1 peduncle article 1 with 2 small processes; article 2 with no process, shorter than article 1; article 3 shortest; accessory flagellum scale-like; primary flagellum of 45 articles. Antenna 2 articles 1–5 lacking distal processes, flagellum with 53 articles.

Mandible. Incisor and lacinia mobilis strongly dentate; molar produced and triturative; palp article 3 densely setose medially, with long stout SS distally. Maxilla 1 medial plate subtriangular, obliquely convex inner margin with 11 stout, plumose SS; lateral plate distal margin oblique, with medially lobate RS; palp strongly exceeding outer plate; palp article 1 short, article 2 slightly curved medially with stout SS distomedially, stout RS distally. Maxilla 2 with long, distally crenulate setae distally on lateral and medial plates. Maxilliped lateral plate broadly rounded distally, medial plate with nodular RS and a row of long plumose SS on medial, anterior face; palp medial margin strongly setose; merus distally slightly expanded; dactyl with serrate medial margin.

Pereopods. Gnathopod 1: coxa 1 long and slender, basis linear, slender, posterior margin with numerous fine SS; merus slightly longer than ischium, anterior margin very short, distal margin oblique, posterodistal angle acute, setose; carpus linear, distal half of posterior margin with long SS; propodus slightly expanded distally, anterior margin naked except for distal fringe of short SS, palm finely crenulate, slightly oblique, with cluster of RS defining rounded distal margin, posterior margin with numerous long SS; dactylus slender, slightly curved, posterior margin strongly serrate. Gnathopod 2: coxa 2 wider than coxa 1, basis linear, ischium anterior margin very short, distal margin obliquely articulating with carpus, carpus linear, anterior margin naked except for transverse row of SS distally, posterior margin with numerous stout SS distally; propodus linear, palm almost transverse, rounded, finely crenulated, lined with numerous submarginal RS; dactylus large, not exceeding palm, posterior margin serrate. Pereopod 3: coxa similar to coxa 2, basis linear, anterior and posterior margin finely setulose; merus slightly expanded distally; carpus shorter than merus, anterior margin naked, posterior margin with 6 pairs of RS; propodus naked anteriorly, posterior margin with 9 pairs of RS; dactylus stout, curved. Pereopod 4: coxa much larger than 3, wide posteroventral angle projecting somewhat ventrally; basis to dactylus as for pereopod 3. Pereopod 5: coxa rectangular; basis bearing posteromarginal tooth; merus drawn out posterodistally; carpus slightly widened distally, posterior margin with 7 pairs of RS; propodus linear, posterior margin with 10 pairs of RS; dactylus curved, stout, approx. 0.3 × propodus length. Pereopod 6: coxa anterior half hidden by coxa 5, anterior margin weakly concave, posterior margin slightly drawn out; basis posteromarginal tooth larger than in pereopod 5; merus drawn out posterodistally, ischium to dactylus as in pereopod 5. Pereopod 7: coxa subrectangular; basis widened distally, but without tooth, only posterodistal angle pointed; ischium to dactylus as in pereopods 5 and 6.

Urosome and telson. Uropod 1: peduncle subequal in length to inner ramus, medial margin with 1 RS distally, distal margin with close row of short RS; inner ramus lateral margin with spaced row of short RS, medial margin with sparse RS; outer ramus marginally shorter than inner. Uropod 2: peduncle with row of short setae; inner ramus nearly twice the length outer ramus, both margins sparse lined with RS; outer ramus, both margins with few short RS. Uropod 3: peduncle short, approx. 0.3 × length of inner ramus, medial and inner margins of both rami with sparse row of short RS. Telson slightly longer than wide, u-shaped emargination 0.2 × lengths, lobes triangular, broadly rounded apically.

Coloration. Freshly captured specimen (s) of Epimeria robustoides show distinct red eyes ( Fig. 10 A ) and some bear orange patches on their bodies.

Figures

Figure 2. Epimeria robustoides sp. n., female, 40 mm. A Lateral habitus B dorsal habitus C labrum D mandibular palp E mandibular body.

Figure 3. Epimeria robustoides sp. n., female, 40 mm. A Maxilla I B frontal face of inner maxillipedal endite C maxilliped. left palp and endites omitted D shape of maxilla 2 E details of maxilla 2 F antenna 2 G antenna 1.

Figure 4. Epimeria robustoides sp. n, female, 40 mm. A Pereopod 1 B pereopod 3 C pereopod 4, medial face, setae omitted D pereopod 4, coxa dissected E pereopod 2, dotted line indicates length of oostegite setae, of which only some examples are given.

Figure 5. Epimeria robustoides sp. n. A Pereopod 6 B telson C pereopod 7 D pereopod 5. coxa dissected E uropod 1 F uropod 2 G coxa and part of basis of pereopod 5 H uropod 3.

Figure 10. A Epimeria robustoides sp. n. Weddell Sea, photographed by Dr. Martin Rauschert on RV Polarstern B-D colour variations of Epimeria robusta from the Ross Sea pictured by Dr. Stefano Schiaparelli on RV Tangaroa B NIWA 37110, TAN0802/117 C NIWA 20270 TAN0402/130 D NIWA 37109, TAN0802/117.