Metopa gigas Just, 2013, sp. nov.
Creators: name: Just, Jean
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Stenothoidae
Metopa
Metopa gigas

description: Metopa gigas sp. nov.
Figs 1–4
Type fixation. Holotype, ♀, here designated.
Etymology. The epithet is the Latin noun for Giant.
Material examined. Holotype, ♀, 19.0 mm, West Greenland, Godthaabsfjord [Kugssukfjord], approximately 64°N 52°W, ca. 300 m, ‘ Tjalfe’ stn 52, 15 June 1908, ZMUC CRU-20522.
Paratypes. Same data as holotype, ZMUC CRU-20523 (15 specimens, juveniles and immature). Southernmost Greenland: S of Akuliaruseq, 60°08.6’N 44°10.7’W, 400– 250 m, rectangular dredge on steep rock face with hydroids, Kap Farvel Expedition, stn 103, 17 August 1970, ZMUC CRU-20524 (1 ♀, 23 immature). Southernmost island in Toqulineq, 60°04.5’N 43°02.7’W, 240 m, stones, gravel, clay, Bryozoa, rectangular dredge, Kap Farvel Expedition, stn 136, 25 August 1970, ZMUC CRU-20525 (1 3, 19.1 mm). Off Sydprøven [Alluitsup Paa], 60°20’N 47°27’W, 120 m, on Hydroida, ottertrawl, ‘ Godthaab’ Expedition, stn 188, 10 October 1928, ZMUC CRU-20526 (1 specimen *). East Greenland: Scoresby Sund, Stewart Land, 70°30’N, 300 m, East Greenland Expedition 1900, 29 July 1900, ZMUC CRU-20527 (1 specimen *). Scoresby Sund, Kap (Cape) Tobin, 70°22’N 22°05’W, 108 m, stones, East Greenland Expedition 1900, 21 August 1900, ZMUC CRU-20528 (1 3, 19.2 mm, 3 immature*). East Greenland Expedition 1900, (no further data, but presumably Scoresby Sund area), ZMUC CRU-20529 (1 immature*). East Greenland Expedition 1900, (no further data, but presumably Scoresby Sund area), ZMUC CRU-20530 (1 immature*). West Greenland: Nordre Strømfjord, ca. 30 km from mouth of fjord, N of Holsteinsborg [Sisimiut], approximately 67°30’N 53°30’W, 200–240 m, V. Nordmann, 1911, stn 3C, ZMUC CRU-20531 (1 specimen *).
Note. Specimens in the ZMUC collections here marked * were reported as Metopa clypeata (Kr) by Stephensen (1931, 1944).
Description. (Based on holotype). Head length (tip of rostrum to pereonite 1) as pereonite 1 and half of 2 combined; interantennal lobe strongly projecting, broadly rounded; eyes small, round, occupying approximately 1/ 3 of head length level with eye; frons projection below the rostrum in a right angled blunt triangle between eye lobes, widely separated from irregularly rounded epistome projecting well beyond upper lip.
Pereonites dorsally with low, broad ‘saddle’ in posterior half, weak in 1 and 2, increasingly more pronounced in more posterior pereonites; pleonites with similar ‘saddle’. Pereonites 1–4 increasing in length, 5–7 of equal length, all slightly shorter than 4. Pleonites 1–3 of subequal length, all about as long as pereonite 7; pleonal side plate 1 ventrally rounded, 2 and 3 rectangularly pointed.
Coxal plate 2 roundedly pointed apex, with weak concavity posterodistally; plate 3 evenly convex distally; plate 4 as long as pereonites 2–5 combined along their ventral margins, 1.8 longer than mid depth; plates 5 and 6 with posterior lobe.
Antenna 1 as long as head, pereonites and pleonites 1 and 2 combined along dorsal curvature; peduncle articles 1 and 2 of equal length; flagellum of 36 articles, each with 2 short aesthetascs. Antenna 2 as long as head, pereonites 1–5 and half of 6 combined, peduncle articles 4 and 5 of equal length, flagellum 4/5 length of peduncle article 5, with about 11 article.
Left mandible lacinia mobilis serrate, nearly as broad as equally serrate incisor; body medially with ridge and low hump; palp of 1 article (probably damaged; see Remarks below). Right mandible incisor as in left; lacinia composed of 2 separate flattened setae; body medially with low hump carrying 5 short, stiff setae; palp of 2 articles, article 1 elongate with lateral row of simple setae; article 2 about 1/5 length of 1, with a few terminal setae. Maxilla 1 palp with row of 11 robust setae in distal half of medial margin and apically, distal surface with cover of small setae and setules; outer lobe with 7 smooth spine-setae. Maxilliped outer plate vestigial; inner plates fused with apical notch and small marginal setae.
Gnathopod 1 slender, merus projecting under carpus; carpus elongate, about twice as long as propodus, densely setose along posterior margin; propodus simple; dactylus short, with row of setae on posterior margin. Gnathopod 2 merus in lateral view with acutely pointed projection covering entire carpus and about 1/5 of propodus, with transverse rows of small robust setae along posterior margin, in medial view with rounded dorsal lobe with a few small robust setae; carpus dorsal margin with row of stridulating knobs, in medial view with anterodorsal acute projection, posterior lobe with fringe of simple setae; propodus as long as basis, slightly widening distally, palm convexly transverse, crenulated, posteriorly defined by deep notch and strong tooth.
Pereopod 3 thin, slightly longer than 4, with short simple setae only. Pereopod 4 robust, posterior margins of merus, carpus and propodus with a few transverse rows of small robust setae. Pereopod 5 basis rectilinear with row of long simple setae in proximal half of anterior margin; merus, carpus and propodus anterior margin with several transverse rows of small robust setae. Pereopods 6–7 basis posteriorly broadly expanded, basis of 6 anterior margin with row of small robust setae, of 7 with a few simple setae; merus, carpus and propodus of both armed as in pereopod 5.
Uropod 1 peduncle slightly longer than urosomite 1, dorsolateral margin with about 21 robust setae, dorsomedial margin with 7 robust setae; outer ramus 0.8 length of peduncle, with 4 dorsal robust setae, inner ramus as long as outer, smooth, both up-curved distally. Uropod 2 peduncle 0.8 length of uropod 1 peduncle, dorsolateral margin with 10 robust setae, dorsomedial margin with a few scattered robust setae; outer ramus 0.75 length of peduncle, slightly up-curved, dorsolaterally with 3 robust setae; inner ramus as long as peduncle, smooth, slightly up-curved distally. Uropod 3 peduncle 2.8 times longer than greatest lateral width, dorsolaterally with 4 robust setae, subequal in length to uropod 2 peduncle, with dorsoapical projection; article 1 of ramus about 2/3 length of peduncle, with dorsoapical group of small robust setae; article 2 of ramus about 4/5 length of article 1, tapering, smooth.
Telson oval, slightly broader in distal half, with 2 blunt robust setae each side in proximal half, single simple seta each side in distal half.
Size. Largest male, 19.2 mm; largest female, 19.1 mm.
Distribution. Southern Greenland, south of approximately 70°N on the west- as well as east coast; 120– 400 m.
Remarks. Males are similar to females. Immature specimens of about 8 mm and juveniles of 5 mm have antenna 1 as long relative to the body as in adults. Immature specimens have small dorsal saddles, while juveniles have only a small rounded bump at the presumptive place.
The palp of the left mandible in the large male from Kap Tobin (CRU-20528) is similar to the right one in the holotype (Fig. 2 md mv r), and it has a setal row as in the right mandible. This indicates that the left mandible of the holotype has been damaged at some point.
description: Published as part of Just, Jean, 2013, Metopa gigas sp. nov. from southern Greenland, a giant among congeners (Crustacea, Amphipoda, Stenothoidae), pp. 289-295 in Zootaxa 3641 (3) on pages 289-294, DOI: 10.11646/zootaxa.3641.3.8, http://zenodo.org/record/224243