Metopa tenuimana 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 : 23-24

Metopa tenuimana Sars, 1892

Metopa tenuimana Sars 1892: 259–60 , pl. 91-1

Metopa tenuimana — Stephensen 1931: 189; Stephensen 1944: 58

Metopa tenuimana — Gurjanova 1951: 433, fig. 278; Shoemaker 1955: 22

Metopa tenuimana — Bousfield 1973: 289; Lincoln 1979: 188, fig. 85i–p; Just 1980: 49, fig 52

Material examined. Morphological examination: F13730 (coll: G.O.Sars, Norv. occid.) 3 mm, female. Syntype .

Type locality: west Norway. Sars (1892) is uncertain where along the west norwegian coast he found the species, as it was confused with samples of M. pusilla .

See figures 1, 60, 61 and 62.

Morphological redescription of female type material.

Head ( Fig. 1B ): small and rounded, cephalic lobe rounded; eye small and round, 1/3 of head length. Antenna 1 ( Fig. 60 ): slim, little less than half body length; peduncle shorter than flagellum, article 1 almost as long as articles 2 and 3 together; flagellum 9-articulate, one longish simple seta at each article; no accessory flagellum observed. Antenna 2 ( Fig. 60 ): broken in examined specimen, but probably longer than antenna 1; peduncle article 4 longer than article 5, flagellum articles longish, but flagellum broken. Mandible ( Fig. 60 ): palp 3-articulate, first article short and third article minute, one simple seta at tip of third article; incisor and lacinia mobilis serrate; raker setae narrow; no molar. Maxilla 1 ( Fig. 60 ): inner lobe small, one seta; outer lobe flat at distal margin, one tooth, three cuspidate setae, inner margin lined with simple setae; palp 1-articulate, distal margin with one tooth, three simple setae, inner margin lined with simple setae. Maxilla 2 ( Fig. 60 ): outer lobe normally placed to inner lobe; inner lobe with four and outer lobe with five simple setae. Maxilliped ( Fig. 60 ): long and slim; inner plates with a slight notch at distal margin, but not separate; outer lobe small, 0.3x palp article 1 length; palp 4-articulate, very few setae, palp article 3 with cushion at distal margin, article 4 lined with simple setae along inner margin.

Pereon ( Fig. 1B ): smooth. Pereopod 1 ( Fig. 61 ): simple; coxa small and subquadrate; basis straight and slim; ischium subquadrate, merus suboval, cushioned with simple setae at posterior margin, two type A setae at distal margin; carpus elongate, posterior margin with long simple setae; propodus elongate and slim, no trace of a palm, longer and narrower than carpus; dactylus slightly curved, smooth, 0.5x propodus length. Pereopod 2 ( Fig. 61 ): coxa suboval, directed forwards and covering coxa 1; basis straight and slim, ischium subquadrate; merus subtriangular; carpus cushioned with short simple setae at posterior margin, distal margin lined with type A setae; propodus elongate, distal margin slightly wider than proximal, palm almost transverse but with distal half cut off and a small tooth at palmar corner set below normal line of palm, one strong seta near palmar corner; dactylus as long as palm, curved, naked. Pereopod 3 ( Fig. 62 ): coxa subrectangular; rest of leg slim and simple; meral lobe 0.2x carpus length; dactylus thin and slightly curved, 0.7x propodus length. Pereopod 4 ( Fig. 62 ): coxa rounded triangular, rest of leg slim and simple; meral lobe 0.2x carpus length, dactylus curved and smooth, 0.7x propodus length. Pereopod 5 ( Fig. 62 ): coxa small, somewhat extended posteriorly; basis slender and straight; meral lobe 0.3x of carpus length; strong setae along anterior margin of leg; dactylus slim and smooth, 0.8x propodus length. Pereopods 6 and 7 ( Fig. 62 ): coxae small, coxa 6 somewhat extended posterodistally; bases expanded posteriorly; meral lobes reaching 0.5x and 0.7x carpus length respectively, dactyli slightly curved and smooth, 0.7x and 0.6x propodus length.

Urosome ( Fig. 1B ): smooth. Epimeral plate 3 ( Fig. 1B ): posterodistal corner acute. Uropod 1 ( Fig. 61 ): longer than uropod 2; biramous; peduncle longer than rami; outer ramus slightly longer than inner. Uropod 2 ( Fig. 61 ): longer than uropod 3; biramous; peduncle longer than rami; outer ramus longer than inner. Uropod 3 ( Fig. 61 ): uniramous; peduncle shorter than ramus, one seta at distal margin; ramus 2-articulate, inner article slightly longer than outer, one seta distally. Telson ( Fig. 61 ): shorter than 2x width, slightly rounded tip, two pairs of cuspidate setae.

Sexual differences: no sexual differences noted.

Distribution: West coast of Norway, Scotland, Shetland, East Greenland, East of Laptev Sea, Alaska, see map Figure 69 N .

Ecology: not much is known about this species, and nothing of its ecology.

The name tenuimana refers to the small gnathopod 2 of this species.

Other Metopa -species in the type-collections. For some of the Metopa -species in the type-collections of the Natural History Museum in Oslo, there have already been made changes that have removed them from Metopa . These are presented in Table 1, with both original authors and authors for the move.

The file cards for the general collections listed Metopa californica Boeck, 1871 , sample F14725, with collection information " California 1871, coll Esm.". The species is described in Boeck (1871b). As this species does not figure in any of the lists of Metopa today, and as it not was listed in the type-collection it is not included in the discussion in this paper.

Figures

FIGURE 1. Photo of Metopa aequicornis Sars, 1879, male, 6 mm, F1806 holotype (A). Photo of Metopa tenuimana Sars, 1892, 3 mm, female, F13730 syntype (B).

FIGURE 60. Metopa tenuimana Sars, 1892, female, 3mm, F13730 (syntype): antenna 1, antenna 2, mandible, maxilla 1, maxilla 2, maxilliped. All scale bars are 0.1 mm.

FIGURE 61. Metopa tenuimana Sars, 1892, female, 3 mm, F13730 (syntype): gnathopod 1, gnathopod 2, uropod 1, uropod 2, uropod 3, telson. All scale bars are 0.1 mm.

FIGURE 62. Metopa tenuimana Sars, 1892, female, 3 mm, F13730 (syntype): pereopod 3, pereopod 4, pereopod 5, pereopod 6, pereopod 7. All scale bars are 0.1 mm.

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