Metopa boeckii 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 : 10-11

Metopa boeckii Sars, 1892

Metopa boeckii Sars 1892: 252–54 , fig. 88

Metopa bruzelii —Boeck 1871, non Metopa bruzelii ( Goës, 1866) : 522

Metopa borealis — Sars 1885 (part)

Metopa boeckii — Stephensen 1926: 68, Stephensen 1928: 164, pl. 30:13–15, Stephensen 1931: 186; Stephensen 1938: 173

Metopa boeckii — Gurjanova 1951: 423–24, fig. 266

Metopa boeckii — Oldevig 1959: 44; Bousfield 1973: 289

Material examined. Morphological examination: F13745 (collect G.O. Sars, Tjøtøy (Helgeland )). Female and male .

Type locality: probably Haugesund, (collected by Boeck and identified by Sars), or Tjøtø, North Norwegian coast .

See figures 14, 15, 16, 17 and 18

Morphological redescription of material collected by original author.

Head ( Fig. 14 ): medium sized and rounded, epistome flat; eyes approximately 1/3 of head length, round, well defined. Antenna 1 ( Fig. 14 ): long and slender, a little longer than half body length; peduncle article 2 longer than article 1; flagellum 12-articulate, longer than flagellum; no accessory flagellum observed. Antenna 2 ( Fig. 14 ): subequal in length to antenna 1; peduncle double length of flagellum, articles 4 and 5 subequal in length; peduncle 12-articulate, naked. Mandible ( Fig. 15 ): palp 2-articulate, oval in cross-section, two simple setae at apex; incisor and lacinia mobilis serrate; no molar. Maxilla 1 ( Fig. 15 ): inner plate somewhat reduced, one simple seta; outer plate narrow, four simple setae at distal margin; palp 1-articulate with one tooth and four cuspidate setae at distal margin. Maxilla 2: this mouthpart was lost. Maxilliped ( Fig. 15 ): long and narrow, naked; inner plates fused; outer plate totally reduced; palp slender, 4-articulate.

Pereon ( Fig. 14 ): smooth. Pereopod 1 ( Fig. 16 ): simple; coxa small, subquadrate; basis long and linear, somewhat flat at anterior margin; ischium subquadrate; merus distally not free, but the posterordistal margin produced a little, few long simple and pectinate setae; carpus elongate, several simple setae along posterior margin, few simple and pectinate setae at distal margin; propodus not as long as carpus but as wide as carpus, no palm, but area dactylus meets is delimited by a row of short simple setae; dactylus curved, few simple short setae at inner margin. Pereopod 2 ( Figs. 16 (female) and 17(male)): coxa covering coxa 1, oval (male) to suboval (female), few simple short setae at posterior margin; basis linear; ischium subquadrate; merus spoonshaped, triangular (male) to elongate (female); carpus spoon-shaped, subtriangular, row of simple setae along distal margin; propodus subtriangular, palm oblique (wider angle in male than in female), serrate (more coarsely so in male) and lined with simple setae, palmar corner set off by a strong tooth and a cuspidate seta, hind margin subequal to palm length; dactylus curved, with a flat naked inner margin. Pereopod 3 ( Fig. 16 ): coxa subrectangular, lined with simple short setae at distal margin; rest of leg thin and elongate with linear basis, very few and simple setae; dactylus simple, reaching 0.6x propodus. Pereopod 4 ( Fig. 17 ): coxa subtriangular, rest of leg simple, slightly thicker than P3 and with more simple setae along posterior margin; dactylus curved and simple, reaching 0.75x propodus. Pereopod 5 ( Fig. 18 ): coxa small, weakly produced posteriorly; basis slender; meral lobe reaching 1/3 of carpus; dactylus curved, thin and simple, reaching 0.6x propodus; anterior margin of leg with short simple setae. Pereopods 6 and 7 ( Fig. 18 ): coxae small, coxa 7 produced towards posterior margin of basis 7; bases posteriorly expanded; meral lobes reaching 0.5x and 0.6x of carpus respectively; dactyli smooth, P7 dactylus curved slightly more than that of P6, both reaching 0.6x propodus; anterior margin of legs with simple setae, more dense in P6 than in P7.

Urosome ( Fig. 14 ): smooth. Epimeral plate 3 ( Fig. 18 ): posterodistal corner slightly acute angle. Uropod 1 ( Fig. 18 ): longer than uropod 2; biramous; peduncle longer than rami, rami subequal in length; very slender, few and simple setae both at peduncle and rami. Uropod 2 ( Fig. 18 ): longer than uropod 3; biramous; peduncle longer than rami, one simple seta at distal margin; rami subequal, outer ramus slightly shorter than inner, one simple seta on inner article. Uropod 3 ( Fig. 18 ): uniramous; peduncle longer and wider than ramus, five simple setae along inner margin; ramus 2-articulate, articles subequal, one simple seta at inner article. Telson ( Fig. 17 ): tongue-shaped, length slightly less than 2x width, two pairs of cuspidate setae.

Sexual differences: Gnathopod 2 is different in male and female, the male having a more coarsely serrate palm with a larger tooth at the palmar corner and the palm more oblique than the female.

Distribution: Arctic to Atlantic: Spitsbergen, Norwegian coast, SE Iceland, West Greenland, Gulf of St. Lawrence, see map Figure 64 D .

Ecology: found at depths from 10–170 m.

The name boeckii refers to Axel Boeck, Sars’ colleague, for whom the species was named.

Other material. Material collected during cruises at Spitsbergen 2005, 2006, 2007 and 2009 has also been examined, and been found to be in compliance with the material from Sars.

Remarks. Sars (1892) comments that he earlier had confused this species with Metopa borealis , and that Boeck must have confused it with M. bruzelii , as his specimens were not in accordance with the specimens Goes had for M. bruzelii . He further mentioned that the slender antennae and the shape of gnathopod 2 (for both sexes) should help distinguish this species from the related species. Also the setation (armature) of uropod 3 and telson are mentioned as distinguishing characters.

Figures

FIGURE 14. Metopa boeckii Sars, 1892, female, 5 mm, F13745: Whole animal. Scale bar is 0.5 mm.

FIGURE 15. Metopa boeckii Sars, 1892, female, 5 mm, F13745: mandible, maxilla 1; male, 4.5 mm, F13745: maxilliped. All scale bars are 0.1 mm.

FIGURE 16. Metopa boeckii Sars, 1892, female, 5 mm, F13745: gnathopod 1, gnathopod 2, pereopod 3. All scale bars are 0.1 mm.

FIGURE 17. Metopa boeckii Sars, 1892, female, 5 mm, F13745: pereopod 4, telson; male, 4.5mm, F13745: gnathopod 2. All scale bars are 0.1 mm.

FIGURE 18. Metopa boeckii Sars, 1892, female, 5 mm, F13745: pereopod 5, pereopod 6, pereopod 7, urosome. All scale bars are 0.1 mm.

FIGURE 64. Distribution map of C: Metopa alderii (Bate, 1857) and D: Metopa boeckii Sars, 1892