Metopa leptocarpa Sars, 1883

Tandberg, Anne Helene S., 2010, A redescription of Metopa species (Amphipoda, Stenothoidae) based on the type material. 3. Natural History Museum, Oslo (NHM) 2465, Zootaxa 2465 (1), pp. 1-94 : 14-15

Metopa leptocarpa Sars, 1883

Metopa leptocarpa Sars 1883: 91 , pl. 4–3; Sars 1892: 265–66, pl. 93-2

Metopa leptocarpa — Della Valle 1893: 639, fig. 59–53

Metopa leptocarpa — Stephensen 1938: 173–74; Gurjanova 1951: 427–28, fig. 269

Material examined. Morphological examination: F13735 (det: G.O.Sars, no locality noted) Holotype, female. The specimen was already dissected.

Type locality: from Sars (1892) it seems the holotype and single specimen in the Oslo collections must come from Kristiansund , north-west coast of Norway, depth 110–145 m.

See figures 29, 30, 31 and 32.

Morphological redescription of female type material.

Head ( Fig. 29 ): small and rounded, cephalic lobe acute, with a small and rounded lobe next to basis of antenna 2; eyes small, 1/3 length of head, and rounded, well defined. Antenna 1 ( Fig. 29 ): short and stocky; peduncle article 1 broader and longer than rest of peduncle, as long as article 2; flagellum 8-articulate, as long as peduncle, two simple setae apically; no accessory flagellum observed. Antenna 2 ( Fig. 29 ): broken in examined material; peduncle as long as all of antenna 1, peduncle article 4 and 5 subequal in length, all of peduncle slimmer than article one of antenna 1 peduncle. Labrum ( Fig. 29 ): rounded. Mandible ( Fig. 29 ): palp missing after dissection, but is drawn on the head-drawing in Sars (1892), even though no mouthparts are described in his text; incisor and lacinia mobilis crenulate but well defined; raker setae broad plates flat and serrate distally; no molar. Maxilla 1 ( Fig. 29 ): inner plate rounded, one simple seta apically; outer plate flat distally, one tooth, two short and three long cuspidate setae, a row of minute simple setae along inner margin; palp 1-articulate, one tooth and one largish cuspidate seta distally, serrate inner margin lined with simple setae. Maxilla 2 ( Fig. 29 ): outer plate in normal position to inner plate, rounded; four and six simple setae distally respectively. Labium ( Fig. 29 ): pointed, lined with simple setae along inner margin. Maxilliped ( Fig. 30 ): long and semislender; inner plates fully separate, two distal simple setae on each lobe; outer plate with a small elongation along inner margin, wider than palp; palp 4-articulate, inner margin of first two articles lined with simple setae, article 3 with a cushion of simple setae at inner distal margin, article 4 lined with simple setae along inner margin.

Pereon: smooth. Pereopod 1 ( Fig. 30 ): subchelate; coxa subquadrate, small; basis elongate, straight, lined with simple setae along anterior margin; ischium and merus short, merus subtriangular with a cushion of short simple setae along posterior margin; carpus elongate and very narrow, 2/3 length of basis and slightly narrower, a few simple setae along posterior margin; propodus narrow and elongate, length almost 4x width, which is slightly flaring at distal margin, palm transverse, smooth, lined with a few simple setae, palmar corner set off by one cuspidate seta; dactylus as long as palm, curved, inner margin naked, three simple setae along proximal outer margin. Pereopod 2 ( Fig. 30 ): coxa suboval; basis straight and linear; ischium subquadrate; merus subtriangular; carpus cup-shaped and subtriangular with a cushion of short simple setae at posterior margin, distal margin with longer simpler setae; propodus subrectangular, palm oblique, smooth with simple setae, palmar corner set off by a tooth and two cuspidate setae, hind margin as long as palm; dactylus as long as palm before tooth, smooth and slightly curved. Pereopod 3 ( Fig. 31 ): coxa subrectangular; basis slender and straight; meral lobe reaching 1/3 of carpal length, dactylus slim and curved, propodus 2.5x dactylus length. Pereopod 4 ( Fig. 31 ): coxa rounded triangular; rest of leg simple; meral lobe reaching 0.4x carpus; dactylus simple and curved, 0.5x propodus. Pereopod 5 ( Fig. 31 ): coxa subquadrate; basis slender and straight; meral lobe 0.6x carpus, two simple setae at distal margin of lobe; dactylus curved and simple, 0.4x propodus. Pereopods 6 and 7 ( Fig. 32 ): coxae small and rounded, coxa 6 slightly elongated posteriorly; bases posteriorly expanded; meral lobes 0.6x and 0.7x carpal length, respectively; both legs with sparse setation of simple short setae mainly along anterior margin; dactyli simple and curved, both with a tiny notch at tip.

Urosome: smooth. Epimeral plate 3: posterodistal corner acute. Uropod 1 ( Fig. 32 ): slightly longer than uropod 2; biramous, peduncle almost 2x rami length, one simple seta at distal margin; rami slightly uneven in length, outer ramus a little shorter than inner ramus. Uropod 2 ( Fig. 32 ): longer than uropod 3; biramous; peduncle almost 3x rami length, one simple seta at distal margin; rami subequal, naked. Uropod 3 ( Fig. 32 ): uniramous; peduncle shorter and wider than ramus, with a small extension at distal margin along ramus; ramus 2-articulate, the articles subequal in length; two setae at inner margin of peduncle and two setae distally at article 1 of the ramus. Telson ( Fig. 31 ): rounded and tongue-shaped, rather broad with length less than 2x width, naked.

Sexual differences: no sexual differences are noted.

Distribution: West Norway (Christiansund, type locality), SW of Iceland, Laptev Sea, see map Figure 66 G .

Ecology: has been found at 20–1505 m depth.

The name leptocarpa refers to the very long carpus on gnathopod 1.

Remarks. This species is very easily distinguishable from other Metopa by the very elongate carpus of gnathopod 1, and to some degree also by the long peduncles of uropods 1 and 2.

Figures

FIGURE 29. Metopa leptocarpa Sars, 1883, female, F13735 (holotype): head, antenna 1, antenna 2, labrum, mandible, labium, maxilla 1, maxilla 2. All scale bars are 0.1 mm.

FIGURE 30. Metopa leptocarpa Sars, 1883, female, F13735 (holotype): gnathopod 1, gnathopod 2, maxilliped. All scale bars are 0.1 mm.

FIGURE 31. Metopa leptocarpa Sars, 1883, female, F13735 (holotype): pereopod 3, pereopod 4, pereopod 5, telson. All scale bars are 0.1 mm.

FIGURE 32. Metopa leptocarpa Sars, 1883, female, F13735 (holotype): pereopod 6, pereopod 7, uropod 1, uropod 2, uropod 3. All scale bars are 0.1 mm.

FIGURE 66. Distribution map of G: Metopa leptocarpa Sars, 1883 and H: Metopa longicornis Boeck, 1871