Megamoera striata, Labay, Vjacheslav S., 2013

Labay, Vjacheslav S., 2013, Review of amphipods of the Melita group (Amphipoda: Melitidae) from the costal waters of Sakhalin Island (Far East of Russia). I. Genera Megamoera Bate, 1862 and Armatomelita gen. nov., Zootaxa 3700 (1), pp. 65-112 : 81-86

Megamoera striata sp. nov.

Figures 10–13 , 34 b

Diagnosis. Pleon segments 1–3 with central tooth and 0–2 lateral denticles on each side; pleons 2 and 3 with central tooth and 2 denticles. Urosome segment 1 with central tooth and 1 lateral denticle; urosome 2 with 2 pairs of short teeth and single cuspidate seta. Telson lobes, proximal subapical notch more on outer margin. Anterior head lobe shallow, lower margin with prominent accessory process. Pereopod 1 (male) broadest distally, palm oblique, sharply angled from posterior margin. Pereopod 2 (male), anterior margin of dactyl strongly setose; palm oblique, convex, with low irregular hinge tooth and stout postero-distal tooth. Maxilla 1, palp segment 1 with 4 lateral setae. Maxilla 2, inner plate, facial setae developed, submarginal in position. Uropod 3, proximal segment of outer ramous slender, with 5–8 clusters of marginal cuspidate setae on each margin.

Type material. Holotype male, 30 mm, X 37859 Cr 1425, north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (51°28.1'N 143°49.5'E, 75 m), silt and sand, M.G. Rogotnev & P.V. Polupanov, 23 July 2010. Paratypes: 3 males, X 37863 Cr 1429 with same data as holotype; 2 males X 37860 Cr 1426, the north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (52°25'N 143°51'E, 101 m), sand, M.G. Rogotnev; 3 males X 37862 Cr 1428, north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (52°24'98N 143°52'518E, 88 m), sand, M.G. Rogotnev.

Type locality. The north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (51°28.1'N 143°49.5'E, 75–85 m).

Description. Known only by males. Male (30 mm). Vital body color maroon with light spots on body segments and with light bands on the segments of the limbs ( Figs. 10 a, 12a, c, d, e, f, 13a, j, k, l). Cuticle (all coxa, basis of pereopods 3–7, epimeral plates 1–3) with cuspidate mictotrichs, each set in a center of hollow ( Fig. 12 g). Pereon segments smooth dorsally, without teeth or humps ( Fig. 10 a, b). Pleon segments 1 with central tooth, without lateral denticles; pleons 2 and 3 with central tooth and 2 denticles. Urosome segment 1 with central tooth and 1 lateral denticle each side; urosome 2 with 2 pairs of short teeth and single cuspidate seta.

Head: ( Figs. 10 c) slightly shorter than pereonites 1 and 2 together with an indistinct rostrum; eyes medium oval, anterior head lobe shallow, inferior margin with prominent lobe; inferior antennal sinus with short notch.

Antenna 1: ( Fig. 10 d) 46% of body length, slender; flagellum exceeding 1.2 length of peduncle, 44 articles, few very thin and short setae scattered along flagellum; peduncle article 1 about as long and double as wide as article 2, article 3 0.2 of article 2 length; accessory flagellum 6-articulate.

Antenna 2: ( Fig. 10 e) flagellum 0.43 times as long as peduncle, 16 articles, very bundle of thin setae on each article; peduncle article 5 shorter than article 4, articles 1 + 2 + 3 shorter than article 5, article 2 with protruding lobe reaching the 2/3 of next article, article 3 with short protruding lobe, articles 4 and 5 with numerous tufts of thin setae spaced evenly along the article.

Mouthparts.

Labrum: ( Fig. 10 f) rounded, frontal margin slightly concave medially, densely covered by minute setae.

Mandible: ( Figs. 10 g, h) incisor crenulate and stretching in a rounded tip; raker setae stout and serrate, numerous (15+), as long as incisor; molar cylindrical triturative, chewing plate striate; palp 3-articulate, palp segments 2 and 3 strongly setose, 1-st article with protruding lobe, the percentage of total length of the articles of the palp are 16% (article 1), 42% (article 2), 42% (article 3).

Labium: ( Fig. 10 i) inner lobes small but well defined, rounded; outer lobes rounded at distal margin.

Maxilla 1: ( Fig. 11 a, b) inner plate subtriangular, lined with a row of simple setae; outer plate elongate, 1.3 as long as inner plate, apically with 2 rows of 9 two-end strong tooth setae; palp 2-articulate, article 2 3.3 times as long as article 1, article 2 apically with two rows of 12–13 simple setae each.

Maxilla 2: ( Fig. 11 c) inner plate slightly shorter than outer plate, facial setae of inner plate developed, closely submarginal, tip covered with numerous simple setae; outer plate with same numerous of simple setae, but only on the tip, subapically with a rare row of 12 setae.

Maxilliped: ( Fig. 11 d) compact; inner plates large, fully cleft, distal margin with a row of 4 teeth, inner and distal margins with long plumose setae; outer plates reaching of the end of palp article 2, inner margin lined with a row of short stout teeth-like setae longer toward the apex, smoothly into the apical row of long thin plumose setae; palp 4-articulate, the percentage of total length of the articles of the palp are 12% (article 1), 46% (article 2), 21% (article 3), 21 (article 4), article 2 with numerouse setae along distal part of inner margine; tip of article 3 with a crown of long simple setae; article 4 inner margin with a line of serrate setae (Watling type IV.1) (Watling 1989).

Pereopod 1: ( Fig. 11 e, f) coxa subrectangular with rounded corners, extended distally; basis straight with a dense row of simple setae along distal part of anterior margins and more rare long setae along posterior margin; merus subrectangular, with a single tuft of plumose setae along posterior margin and with a cushion of short setae along distal part of posterior margin, distal margin with a row of long simple setae; carpus long, 1,2 times as long as propodus, 13–14 oblique rows of long serrate setae along outer posterior margin, with a row of long setae along anterior and posterior parts of distal margin and with tomentose spot at the anterior-distal corner; propodus suboval, broadest distally, with numerous groups of long serrate setae along posterior margin, with 6 tufts of long simple setae along anterior margin and with a dense bunch of long simple setae at the anterior distal corner, palm oblique and minutely serrate with a row of short thin simple setae and rare long setae along palmar margin, sharply angled from posterior margin, inner side near palmar corner with a row of three small cuspidate setae; dactylus as long as palm, curved, with a row of spines along posterior margin, with nail.

Pereopod 2: ( Figs. 12 a, b) coxa rounded subrectangular; basis straight, more longer than coxa, with a rare row of simple setae along posterior margin and with numerous long setae along distal part of anterior margin; merus subrectangular with distinct acute protrusion at the posterior distal corner, with a single tuft of simple setae at the posterior margin and with two long setae at the distal-posterior corner; carpus triangular, 2 times shorter than propodus; propodus subrectangular, palm oblique, convex, with low irregular hinge tooth and stout postero-distal tooth, inner face of anterior margin lined with several groups of serrate setae, posterior margin with numerous tufts of serrate setae, palm with small simple setae, and with a dense cluster of serrate setae; dactylus as long as oblique part of palm, curved to the inside of propodus, inner margin with a rare row of short simple setae, outer margin strongly setose, tip of dactylus with obtuse nail.

Pereopod 3: ( Fig. 12 c) coxa similar size as coxa 2, suboval; basis long linear with few minutely setae along anterior and posterior margins and with rare long simple setae along proximal part of posterior margin; merus long with 2 cuspidate setae along anterior margin and with a cluster of 2 cuspidate setae at the anterior distal corner, posterior margin with three bunches of long setae and with a crown of long setae at the distal corner; carpus 2/3 as lon as merus, with 3 bunches of cuspidate setae along posterior margin; propodus linear, more narrow and as long as carpus, with 4 bunches of cuspidate setae along posterior margin; dactylus medium (0.4 of propodus), with nail.

Pereopod 4: ( Fig. 12 d) similar to that of the pereopod 3; coxa as long as coxa 3, slightly broaded distally, lower margin oblique, posteriorly slightly excavated.

Pereopods 5–7 elongated from pereopod 5 to pereopod 7.

Pereopod 5: ( Fig. 12 e) coxa with rounded front margin, with quadrate hind margin and anterior lobe pulled back and down; basis expanded, with posterior wing and slightly produced posterior-distal lobe, anterior and posterior margins subparallel, width 3/4 length, posterior distal corner rounded, hind margin crenulated, anterior margin with small cuspidate setae; ischium subquadrate; merus slightly broaded medially, with two small cuspidate setae at posterior and anterior margins each, and with a cluster of 2 small cuspidate setae at posterior and anterior distal corner each; carpus 0.85 as long as merus, with 3 groups of 2 cuspidate setae at the anterior margin and with a single clusters of cuspidate setae at the anterior and posterior distal corners each; propodus linear, more narrow and 0.85 times as long as carpus, with 2 bunches of cuspidate setae along anterior margin and with four clusters of small cuspidate setae along posterior margin; dactylus small (1/4 of propodus), with nail.

Pereopod 6: ( Fig. 12 f) coxa with quadrate hind margin and with anterior lobe pulled back and down; basis expanded, with posterior wing, rounded posteriorly, width 0.67 as long, posterior distal corner obtuse, rounded, hind margin crenulated, anterior margin with small cuspidate setae; ischium subquadrate; merus and carpus similar as in pereopod 5; propodus linear, more narrow and 0.85 times as long as carpus, with 4 bunches of cuspidate setae along anterior margin; dactylus small (1/3 of propodus), with nail.

Pereopod 7: ( Fig. 13 a) coxa small, without distinct anterior lobe and with rounded posterior lobe; basis expanded, with rounded posterior wing, width 0.67 length, posterior distal corner obtuse, rounded, hind margin crenulated, anterior margin with small cuspidate setae; ischium subquadratic; merus and carpus similar to that of pereopods 5 and 6; propodus linear, more narrow and as long as carpus, with 4 bunches of cuspidate setae along anterior margin; dactylus small (1/3 of propodus), with nail.

Coxal gills 2–6. Coxal gill 6 smaller than gill 5.

Epimeral plates: ( Fig. 13 b, c, d) plate 1 rounded triangular with 1 diagonal ridge, posterior margin slightly convex, hind corner obtuse; plate 2 hind corner rectangular, posterior margin straight, ventral margins convex, with oblique crest, posterior margin with 3–4 notches, ventral margin with a row of 4–5 small cuspidate setae; plate 3 hind corner moderately produced, acute, posterior margin concave, with 3 notches, ventral margin with a row of 5 small cuspidate setae.

Pleopods ( Fig. 13 e–i): normal; peduncle with two specific toothed setae on the inner corner; inner ramus slightly longer than outer, basis of inner ramus with 8–9 specific stout two-pointed plumose setae along inner margin.

Uropod 1: ( Fig. 13 j) peduncle with strong and curved interramal spur; ramie subequal in length, slightly shorter than peduncle length; peduncle and ramie with tiny simple setae along outer edge, both ramie with a single tiny simple seta at tip each.

Uropod 2: ( Fig. 13 k) peduncle shorter than outer ramous (0.79 ramous length); inner ramous shorter than outer, with numerous simple cuspidate setae along outer margin; uropod 2 shorter than uropod 1.

Uropod 3: ( Fig. 13 l) peduncle shorter than peduncle of uropod 1, with two cuspidate simple seta in 2/3 of posterior margin length and with a row of simple cuspidate setae at the apex; elongate 2-articulate outer ramus (10 length of inner ramus, 1.5 times as long as urosome), with 8 tufts of small cuspidate setae along the anterior margin and with 5 tufts of small cuspidate setae along the posterior margin of article 1, article 2 minutely, slightly longer than crowning setae; inner ramous short and ovoid with one cuspidate seta subapically.

Telson: ( Fig. 13 m) fully cleft; lobes stout, diverging distally; proximal notch positioned laterally; apical and subapical simple cuspidate setae medium.

Etymology. Species name striata based on a Latin word “ striata ” (striped), which is explained by living coloration of it species: with light stripes on body segments and legs. The name is feminine in gender.

Ecology: M. striata was found in the depth interval 75–85 m on the silt-sand bottom in the layer of constant low temperature (-1.2 to +0.5°C).

Distribution: Only type locality. The north-east shelf of Sakhalin Island, Okhotsk Sea.

Remarks. Megamoera striata sp. nov. is most similar to M. glacialis Jarret & Bousfield, 1996 and M. borealis Jarret & Bousfield, 1996 by the dorsal sculpture of pleon segments 2, 3 and urosome segments. Megamoera striata differs from M. glacialis by absence of lateral dorsal teeth on the pleon segment 1, in the shape and armament of telson (proximal notch positioned laterally) and in the form and length of outer ramous of uropod 3 (long, 1.5 times longer than urosome). It differs from M. borealis in having of subacute processes on the low margin of anterior head lobe, by absence of lateral dorsal teeth on the pleon segment 1, in the size of central dorsal tooth of pleon segments 2 and 3 (more than lateral teeth), in the shape and armament of telson (proximal notch positioned laterally). Although the dorsal armament of pleon segments 1–3 and of urosome segments 1 and 2 are more similar between M. striata and M. similidentata , the shape of bases of pereopods 5–7 (expanded, rounded posteriorly) and pointed sculpture of surface M. striata distinguishes these species.

Figures

FIGURE 10. Megamoera striata sp. nov., holotype, male: a—lateral view with coloration, b—carination of body, c—cephalon, d—antenna 1, e—antenna 2, f—upper lip; g—right mandible, h—left mandible, i—lower lips; scale: a— 5 mm; d – i— 1 mm.

FIGURE 11. Megamoera striata sp. nov., holotype, male: a—left maxilla 1, b—pulp of right maxilla 1, c—maxilla 2, dmaxilliped, e—pereopod 1, f—dactylus and palmar margin of pereopod 1, iner side; scale: a, c, d, e, f— 1 mm; b— 0.1 mm.

FIGURE 12. Megamoera striata sp. nov., holotype, male: a—pereopod 2 with coloration, b—dactylus and palmar margin of pereopod 2, iner side, c—pereopod 3 with coloration, d—pereopod 4 with coloration, e—pereopod 5 with coloration, fpereopod 6 with coloration, g—structure of punctuation; scale— 1 mm.

FIGURE 13. Megamoera striata sp. nov., holotype, male: a—pereopod 7 with coloration, b—epimer 1, с—epimer 2, depimer 3, e—pleopod 3, f—coupling spines of pleopod 3, g, h, i—coupling setae of pleopods 1, 2, 3, j—uropod 1 with coloration, k—uropod 2 with coloration, l- uropod 3 with coloration, m—telson; scale: a – e, j – m— 1 mm; f – i— 0.1 mm.

FIGURE 34. Dorsal carination of new species of genera Megamoera and Armatomelita: a— Megamoera similidentata sp. nov., holotype, male, b— Megamoera striata sp. nov., holotype, male, c— Megamoera falsomikulitschae sp. nov., paratype, female, d— Megamoera aequidentata sp. nov., holotype, female, e— Armatomelita tshayensis sp. nov., holotype, male; scale: a, b— 2 mm, c, d, e— 1 mm.