Metopa majuscula Gurjanova, 1948

Tandberg, Anne Helene S., 2009, A redescription of Metopa species (Amphipoda, Stenothoidae) based on the type material. 2. The United States National Museum of Natural History (NMNH), Zootaxa 2309, pp. 43-68 : 53-58

Metopa majuscula Gurjanova, 1948

Metopa majuscula Gurjanova 1948: 283 , fig 2

Metopa majuscula Gurjanova 1951: 436 –37, figs 282, 283

Type locality: Japan Sea ( Gurjanova, 1948)

Material examined. Morphological examination: Albatross station 5016-64. 1906 Sept 26, Okhotsk Sea, 46°44’30”N, 143°45’E. male, 6mm. ID by Shoemaker.

See figures 8, 9, 10 and 11.

Morphological description. Male, 6mm.

Head ( Fig. 9 ): small and rounded, epistome weakly pointed; eyes approximately 1/3 head length, round, well defined. Antenna 1 ( Fig. 9 ): long and slender; slightly shorter than body-length; peduncle articles 1 and 2 subequal length; flagellum 30-articulate, double length of peduncle; no accessory flagellum observed. Antenna 2 ( Fig. 9 ): slender, much shorter than antenna 1; peduncle article 4 slightly longer than article 5; flagellum shorter than peduncle, 15-articulate, each with a short simple seta. Mandible ( Fig. 9 ): palp 3- articulate, article 2 longest, article 3 small, cross-section circular; incisor serrate and well defined, lacinia mobilis well defined with deep incision in middle, serrate edge; no molar. Maxilla 1 ( Fig. 9 ): inner plate small and squarish, one simple seta; outer plate with four cuspidate, one serrate and one conate seta and one tooth; palp slightly longer than outer plate, broad, 1-articulate, row of six cuspidate setae apically. Maxilla 2 ( Fig. 9 ): outer plate in normal position to inner plate; inner plate with seven and outer plate with nine long and four shorter simple setae apically. Maxilliped ( Fig. 9 ): long and slender; inner plates well separated, one conate and two simple setae apically; outer plate very small; palp 4-articulate, series of simple setae along inner margin, article 4 triangular in cross-section with short simple setae along inner margin.

Pereon ( Fig. 8 ): smooth. Gnathopod 1 ( Fig. 10 ): subchelate; coxa suboval, small; basis linear, ischium subquadrate; merus distally free, posterior margin cushioned with thick-set setae; carpus long and slender, long simple setae along posterior margin; propodus distally widened, palm transverse, palmar corner rounded, short simple setae on the smooth palm, long simple setae along posterior margin, which is 2x palm length; dactylus 3-dimensional (as in article 4 of mxp palp), row of short thick setae at inner margin, as long as palm. Gnathopod 2 ( Fig. 10 ): coxa covering coxa 1, directed forwards, subrectangular; basis with "flat" front, triangular cross-section; ischium short and bare; merus triangular with few setae on posterior margin; carpus short, cup-shaped, with a strong row of type A setae along outer distal margin; propodus elongate and widened, basically subquadrate, palm transverse, convex, crenulate, ending in a strong tooth at palmar corner, few simple setae along palm, posterior margin almost 2x palm, near parallel with anterior margin; dactylus smooth, with a series of very short setae along inner margin, reaches to but not over palmar corner tooth. Pereopod 3 ( Fig. 11 ): coxa suboval, slightly longer than coxa 2; rest of leg thin and elongate with linear basis, few and simple setae; dactylus simple, reaching 0.7x propodus. Pereopod 4 ( Fig. 11 ): coxa triangulate; rest of leg simple, thicker than P3, few simple setae along margins; meral lobe reaching 0.5x carpus length; dactylus posterior margin crenulate, reaching 0.6x propodus. Pereopod 5 ( Fig. 11 ): coxa small, somewhat extended posteriorly; basis slender, row of simple setae along posterior margin; meral lobe reaching 0.4x carpus; dactylus reaching 0.5x propodus, with small notch at distal anterior margin. Pereopods 6 and 7 ( Fig. 11 ): coxae small; bases posteriorly expanded; meral lobe reaching 0.9x and 1.1x carpal length, respectively; dactyli with crenulate anterior margins, with an extra notch at distal ends, each reaching approximately 0.6x propodus length; few and simple setae along both legs margins.

Urosome ( Fig. 10 ): smooth. Epimeral plate 3 ( Fig. 10 ): rounded, margins at a sharp angle. Uropod 1 ( Fig. 11 ): longer than uropod 2; biramous; peduncle slightly shorter than rami; rami subequal; rows of simple setae along both keels on peduncle and inner margins of rami. Uropod 2 ( Fig. 11 ): longer than uropod 3; biramous; rami longer than peduncle, inner ramus longer than outer; few simple setae on propodus and rami. Uropod 3 ( Fig. 11 ): uniramous; peduncle slightly shorter than ramus, ramus with two articles, inner article longer; peduncle with one short seta and ramus with four simple short setae on inner article. Telson ( Fig. 11 ): rounded, flat; three pairs of short strong setae.

Ecology: there are no published data on the ecology.

Distribution: t his is known from Gurjanovas type location in the Japan Sea, in the Bering Sea ( Gurjanova, 1951) and the Albatross-station in the Okhotsk-sea.

Figures

FIGURE 8. Metopa majuscula Gurjanova, 1948, male, 6 mm, Albatross st. 5016 - 64: whole animal. Scale bar is 0.5 mm.

FIGURE 9. Metopa majuscula Gurjanova, 1948, male, 6 mm, Albatross st. 5016 - 64: head, maxilla 1, maxilla 2, left and right mandible, maxilliped. All scale bars are 0.1 mm.

FIGURE 10. Metopa majuscula Gurjanova, 1948, male, 6 mm, Albatross st. 5016 - 64: gnathopod 1, gnathopod 2, urosome. All scale bars are 0.1 mm.

FIGURE 11. Metopa majuscula Gurjanova, 1948, male, 6 mm, Albatross st. 5016 - 64: pereopod 3, pereopod 4, pereopod 5, pereopod 6, pereopod 7, uropod 1, uropod 2, uropod 3, telson. All scale bars are 0.1 mm.