Metopa sinuata Sars, 1892

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 : 22-23

Metopa sinuata Sars, 1892

Metopa sinuata Sars 1892: 263–64 , pl. 92-2

Metopa sinuata — Stebbing 1906: 174

Metopa sinuata — Stephensen 1931: 180; Stephensen 1938: 169; Stephensen 1944: 55

Metopa sinuata — Gurjanova 1951: 422–23, fig. 263; Dunbar 1954: 724–25, fig. 6; Oldevig 1959: 45

Material examined. Morphological examination: F1807 (det: G.O.Sars, Station 280, Bjørnøya, 04.07.1878, Norwegian North Atlantic Expedition) female. (20 eggs)

F13864 (det: G.O.Sars, no locality) male.

Photo: F13720 Syntype .

Type locality: probably Kvaløy in Nordland, north Norway, the locality for the syntype F13720, and mentioned as the first locality in Sars (1892) .

See figures 56, 57, 58 and 59.

Morphological redescription of female material identified by author.

Head ( Fig. 56 ): small and round; eyes small and round, 1/3 of head length. Antenna 1 ( Fig. 57 ): shorter than 1/3 of body-length, stout; peduncle as long as flagellum, article 1 as long as articles 2 and 3 combined; flagellum 10-articulate, each with one simple seta; no accessory flagellum observed. Antenna 2 ( Fig. 57 ): slightly longer than antenna 1; flagellum shorter than peduncle, peduncle articles 4 and 5 subequal in length; flagellum 9-articulate, the four most distal articles with simple setae. Mandible ( Fig. 57 ): palp 1-articulate, broad at basis, three setae; incisor and lacinia mobilis serrate, raker setae narrow, no molar. Maxilla 1 ( Fig. 57 ): inner plate small and rounded, one simple seta; outer plate flat at distal margin, one tooth, three cuspidate setae, one serrate seta; palp 1-articulate, one tooth on distal margin, 10 small single setae. Maxilla 2 ( Fig. 57 ): outer plate in normal position to inner plate, inner plate with three and outer plate with seven simple setae. Maxilliped ( Fig. 57 ): long and narrow; inner plates fully separate, two simple setae distally on each; outer plates almost totally reduced, small knobs reaching 0.1x palp article 1, one long seta at each plate-knob; palp 4-articulate, with long simple setae along inner margins and short thin simple setae along ourter margins, article 3 with a small cushion of very short and thin setae at distal margin, article 4 lined with short simple setae along inner margin.

Pereon ( Fig. 56 ): smooth. Pereopod 1 ( Fig. 58 ): simple; coxa subquadrate; basis straight and narrow; ischium subquadrate; merus suboval, distally free, posterior margin cushioned with short setae, distal margin with three long type A setae and four simple setae; carpus elongate, long simple setae along posterior margin; propodus not as long as carpus and a little less wide, no palm, hind margin with seven straight simple setae; dactylus narrow and curved, naked. Pereopod 2 ( Fig. 58 ): coxa suboval, directed forwards, covering coxa 1, five simple setae along posterior margin; basis straight with flat anterior margin; ischium subtriangular; merus spoon-shaped, distal margin with long simple setae; carpus subtriangular, distal margin lined with type A setae; propodus subrectangular, palm oblique, palm with simple setae and palmar corner with a small tooth and a thicker seta, hind margin longer than palm; dactylus strong, flat inner margin with small simple setae along middle. Pereopod 3 ( Fig. 58 ): coxa subrectangular, four small simple setae along posterodistal margin; rest of leg slim and simple; meral lobe 0.1x carpal length; dactylus slim and slightly curved, 0.7x propodus length. Pereopod 4 ( Fig. 58 ): coxa subtriangular, distal margin sinuate; rest of leg slim and simple, with more simple setae along both anterior and posterior margin than P3; meral lobe 0.2x length of carpus; dactylus curved and smooth, 0.6x propodus length. Pereopod 5 ( Fig. 59 ): coxa small, posteriorly slightly extended; basis slim and straight; meral lobe 0.5x carpal length; dactylus smooth and curved at tip, 0.7x propodus length. Pereopods 6 and 7 ( Fig. 59 ): coxae small; bases extended posteriorly, P7 basis almost round; meral lobes 0.8 and 0.7x carpal lengths respectively; dactyli smooth and curved slightly at the tip, 0.6x and 0.7x propodus lengths.

Urosome ( Figs. 56 and 59 ): smooth. Epimeral plate 3 ( Fig. 59 ): posterodistal corner acute. Uropod 1 ( Fig. 59 ): longer than uropod 2; biramous; peduncle longer than rami, six setae along inner margin; rami subequal. Uropod 2 ( Fig. 59 ): longer than uropod 3; biramous; peduncle longer than rami, six setae along inner margin; outer ramus shorter than inner ramus. Uropod 3 ( Fig. 59 ): uniramous; peduncle longer than ramus, four setae along inner margin; ramus 2-articulate, inner article longer than outer, one seta distally. Telson ( Fig. 59 ): rounded with somewhat pointed tip, three pairs of cuspidate setae; almost twice as long as broad.

Sexual differences: gnathopod 2 propodus male with a more oblique and more setose palm, with palmar corner more strongly defined by thick setae, carpal lobe more free from propodus.

Distribution: Ungava Bay, Greenland (west and east), Spitsbergen, Franz Joseph-land, Norwegian coast, Faroe Islands, North Sea, see map Figure 69 M .

Ecology: known from cold water, Stephensen (1938) notes the species found on Diphasia fallax . Depths are usually littoral to sublittoral.

The name sinuata refers to the sinuous distal edge of the coxa 4.

Remarks. As M. sinuata , like M. invalida and M. palmata has a 1-articulate mandible palp it is logical to suggest that also this species should be considered removed from Metopa . As mentioned above, this will be examined in a forthcoming paper (Tandberg & Vader in prep), for which this paper is a preparatory work.

Figures

FIGURE 56.Metopa sinuata Sars, 1892, photo of F13720, syntypes female (A), male (B).

FIGURE 57. Metopa sinuata Sars, 1892, female, F1807: antenna 1, antenna 2, mandible, maxilla 1, maxilla 2, maxilliped. All scale bars are 0.1 mm.

FIGURE 58. Metopa sinuata Sars, 1892, female, F1807: gnathopod 1, gnathopod 2, pereopod 3, pereopod 4; male, F13864: gnathopod 2. All scale bars are 0.1 mm.

FIGURE 69. Distribution map of M: Metopa sinuata Sars, 1892 and N: Metopa tenuimana Sars, 1892

FIGURE.59 Metopa sinuata Sars, 1892, female, F1807: pereopod 5, pereopod 6, pereopod 7, urosome, telson. All scale bars are 0.1 mm.