Quasimelita serraticoxae, Labay, Vjacheslav S., 2014

Labay, Vjacheslav S., 2014, Review of amphipods of the Melita group (Amphipoda: Melitidae) from the coastal waters of Sakhalin Island (Far East of Russia). II. Genera Quasimelita Jarrett & Bousfield, 1996 and Melitoides Gurjanova, 1934, Zootaxa 3869 (3), pp. 237-280 : 259-269

Quasimelita serraticoxae sp. nov.

Figures 1 , 16–23 , 30 c, d

Diagnosis. Pleon segments 2 and 3 with small single mid-dorsal tooth each. Urosome segment 1 with mid-dorsal tooth; urosome 2 with 2 pairs of short dorsal teeth, with single cuspidate seta among each lateral pair. Anterior margin of head truncated, without distinct anterior head lobe, lower antennal corner acute, pointed, lower margin with prominent accessory process. Eye small, round, poorly distinguishable, with pale ommatidia. Coxa 1 with acute, pointed anterior corner; anterior margins of all coxae with distinct serrations. Coxal plates 1 and 2 longer than plates 3 and 4. Propodus of pereopod 1 (male) relatively small, shorter than carpus, not broad distally, palm oblique, pass into the posterior margin without distinct angle; smooth palm that is armed distally with numerous closely set small cuspidate setae. Pereopod 2 (male), anterior margin of dactyl strongly setose; palm oblique, incorrectly toothed, with strong tooth at the palmar angle, with stout short simple setae along the palmar margin, and with clusters of long simple setae. Maxilla 1, inner plate with 8 marginal setae; palp segment 1 with 3–5 lateral setae. Maxilla 2, facial setae of inner plate very reduced (4–5 setae), lined in distal half of inner margin, closely submarginal. Uropod 3 is medium length, peduncle only 1.6 times shorter than outer ramous, proximal segment of outer ramous with 4–5 clusters of marginal stout simple setae; terminal segment distinct, short, length as 1/7 of proximal segment. Telson lobes with acute tips.

Type material. Holotype male, 8.5 mm, 41805/Cr-1510, north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (51°19'16''N 144°0'10''E, 116 m), silt, I.N. Moukhametov, 19 June 2013. Paratypes: 1 female, 7.5 mm, 41806/Cr-1511, with same data as holotype; 11 males and 15 females 41807/Cr-1512, with same data as holotype; 1 male 41808/Cr-1513, north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (52°19'N 144°19'E, 218 m), silt, M.G. Rogotnev & P.V. Polupanov, 11 July 2010; males and females 41810/Cr-1515, northeast shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (52°16'11''N 144°12'46''E, 159 m), silt, I.N. Moukhametov, 30 August 2013; males and females 41809/Cr-1514, Kashevarova shoal, Okhotsk Sea, Far East of Russia (57°32'N 143°47'E, 182 m), silt, V.Iu. Lalov, 11 August 2013.

Type locality. The north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (100–220 m).

Description. Male (8.5 mm). Vital body color is grey-olive. Cuticle (body, all coxa, basis of pereopods 3–7, epimeral plates 1–3) with cuspidate single sensible setae ( Fig. 16 f) and with rare specific setae: stalk with prominent protrusion, from the top of the stalk tillering diverge few simple long branches ( Fig. 23 e, f). Pereon segments smooth dorsally ( Fig. 16 a, b). Pleon segment 1 without teeth; pleon 2 with small mid-dorsal tooth; pleon segment 3 with very small central denticle. Urosome segment 1 with large tooth pulled back; urosome segment 2 with two dorsolateral pairs of small teeth and with single cuspidate seta among each lateral pair.

Head: ( Figs. 16 c) slightly shorter than pereonites 1 and 2 together with an indistinct rostrum; eye small, round, poorly distinguishable; anterior margin of head truncated, without distinct anterior head lobe, lower antennal corner acute, pointed, lower margin with prominent accessory process.

Antenna 1: ( Fig. 16 d) 36% of body length, slender; flagellum 0.6 times length of peduncle, 15 articles, few very thin and short setae scattered along flagellum; peduncle article 1 about as long and double as wide as article 2, with two strong simple setae along lower margin, and with acute short protrusion at the distal margin, article 3 1/3 of article 2 length; accessory flagellum 3-articulate.

Antenna 2: ( Fig. 16 e) flagellum 0.27 times as long as peduncle, 8 articles, bundle of thin setae on each article; peduncle article 5 shorter than article 4, articles 1 + 2 + 3 shorter than article 5, article 1 with upper and lower protruding lobes reaching the 0.4 of article 3, article 3 with short protruding lobe, articles 3, 4 and 5 with numerous tufts of thin setae spaced evenly along the article.

Mouthparts.

Labrum incised.

Mandible: ( Figs. 17 a–f) incisor crenulate and stretching in a rounded tip; raker setae stout and serrate, numerous (7+), as long as incisor; molar cylindrical triturative, chewing plate flattened; palp 3-articulate, palp segments 2 and 3 poorly setose, 1-st article without protruding lobe, the percentage of total length of the articles of the palp are 17–19% (article 1), 39–43% (article 2), 40–42% (article 3).

Labium: ( Fig. 17 g) inner lobes small but well defined, rounded; outer lobes rounded at distal margin.

Maxilla 1: ( Fig. 17 h, i) inner plate suboval, lined with a row of 8 simple setae; outer plate elongate, 1.5 as long as inner plate, apically with 2 rows of 9 two-end strong tooth setae; palp 2-articulate, article 2 2–2.3 times as long as article 1, article 2 apically with two rows of 8–10 simple setae each.

Maxilla 2: ( Fig. 18 a) inner plate slightly shorter than outer plate, facial setae of inner plate reduced (4 setae), closely submarginal, tip covered with numerous simple setae; outer plate with numerous simple setae on the tip, subapically with a rare row of 12 setae.

Maxilliped: ( Fig. 18 b) compact; inner plates large, fully cleft, distal margin with a row of 3 teeth and with a row of cuspidate setae, inner margin with long plumose setae (4–6 setae); outer plates almost reaching of distal margin of palp article 2, inner margin lined with a row of short stout teethlike setae longer toward the apex, smoothly into the apical row of long thin plumose setae, with numerous transverse clusters of short strong simple setae; palp 4-articulate, the percentage of total length of the articles of the palp are 16% (article 1), 44% (article 2), 22% (article 3), 17 (article 4), article 2 with numerouse setae along distal part of inner margine; tip of article 3 bilobed with a row of long simple setae, densely bushy near the base of article 4; article 4 inner margin with a line of serrate setae (Watling type IV.1) ( Watling 1989).

Pereopod 1 (gnathopod 1): ( Fig. 18 c) coxa extended distally, with pointed anterior corner, the anterior margin is distinctly serrated; basis straight with a row of simple setae along anterior and posterior margins each; merus subrectangular, with a cushion of short setae along distal part of posterior margin, distal margin with a row of long simple setae; carpus long, 1.4 times as long as propodus, 7–8 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, with numerous groups of long serrate setae along posterior margin, with 4 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 numerous short thin simple setae and with two subpalmar rows of long setae, smoothly passes in posterior margin; dactylus as long as palm, slightly curved, with a row of small setae along posterior margin, with nail.

Pereopod 2 (gnathopod 2): ( Figs. 18 d) coxa with subparallel anterior and posterior margins, front angle slightly drawn down, pointed, anterior margin with reduced serration; basis straight, longer than coxa, with a row of long simple setae along posterior margin and with more rare setae along anterior margin; merus subrectangular with distinct acute protrusion at the posterior distal corner, with a single simple seta at the posterior margin and with a row of long setae at the distal-posterior corner; carpus triangular, 1.6 times shorter than propodus, with 5 tufts of long setae along posterior margin; propodus suboval, palm oblique, with distinct postero-distal tooth, anterior margin lined with 7 groups of long setae, posterior margin with 8 tufts of serrate setae, palm teethed, with rare strong short setae, with a row of long serrate setae at the palm corner, and with 7 subpalmar clusters of long setae; dactylus as long as oblique part of palm, curved to the inside of propodus, outer margin strongly setose, tip of dactylus with acute nail.

Pereopod 3: ( Fig. 19 a) coxa 1.5 times shorter than coxa 2, slightly narrowed distally, front angle slightly drawn down, with 1–2 notches on the anterior and posterior corners; basis long, with concave anterior and convex posterior margins, with rare minute setae along anterior margin, and with rare long simple setae along posterior margin; merus long with two long and one small thin setae along anterior margin and with a single cuspidate setae at the anterior distal corner, posterior margin with three bunches of long setae and with a tuft of long setae at the distal corner; carpus of 0.85 length of merus, with 6 clusters of long setae along posterior margin; propodus linear, more narrow and of 0.83 as long as carpus, with 5 bunches of long setae along posterior margin; dactylus medium (0.46 of propodus), with acute nail.

Pereopod 4: ( Fig. 19 b) similar to that of the pereopod 3; coxa as long as coxa 3, subquadrate, anterior and posterior corners rounded, anterior and posterior margins with 2 notches distally each, posteriorly slightly excavated.

Pereopods 5–7 elongated from pereopod 5 to pereopod 6, pereopods 6 and 7 equal in length.

Pereopod 5: ( Fig. 19 c) coxa with rounded front margin, with quadrate hind margin and anterior lobe pulled back and down, front margin distinctly serrated; basis elongated, with straight posterior wing and with rounded posterior distal corner, anterior and posterior margins subparallel, width is 0.5 of length, hind margin crenulated, anterior margin with small cuspidate setae; merus slightly broaded medially, with two small cuspidate setae at posterior margin, and with 4 tufts of thin setae along anterior margin, and with a cluster of 2 small setae at posterior and anterior distal corner each; carpus 0.85 as long as merus, with 3 groups of cuspidate setae at the anterior margin and with a single cluster of cuspidate setae at the anterior and posterior distal corners each; propodus linear, narrow and subequal to carpus length, with 5 bunches of long setae along anterior margin; dactylus small (0.33 of propodus length), with nail.

Pereopod 6: ( Fig. 19 d) coxa with rounded hind margin and with anterior lobe pulled back and down; basis slightly expanded, with posterior wing, rounded at the posterior distal corner, width is 0.5 as length, hind margin straight, crenulated, anterior margin convex, with small cuspidate setae; merus similar as in pereopod 5.

Pereopod 7: ( Fig. 19 e) coxa small, without distinct anterior lobe and with rounded posterior lobe; basis expanded, with rounded posterior wing, width is 0.58 of length, posterior distal corner obtuse, rounded, posterior margin crenulated, anterior margin with small cuspidate setae; merus similar to that of pereopods 5 and 6.

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

Epimeral plates: ( Fig. 20 a) hind corner acuminate; plate 1 is rounded anteriorly, posterior margin with 2–3 notches, hind corner slightly produced with small tooth; plate 2 ventral margin convex, posterior margin with 2–3 notches, ventral margin with a row 6–7 strong simple setae; plate 3 hind corner produced, acute, posterior margin straight, ventral margin convex, with a row of 12 strong simple setae.

Pleopods ( Fig. 20 b–g): normal; peduncle with dense row of numerous setae, and with two specific toothed setae or with one specific toothed seta and one strong cuspidate seta on the inner corner; inner ramus slightly longer than outer, basis of inner ramus with 4–6 specific stout two-pointed plumose setae along inner margin.

Uropod 1: ( Fig. 20 h) peduncle with strong and curved interramal spur; rami subequal in length, slightly shorter than peduncle length; peduncle and rami with tiny simple setae along outer edge, both rami with few tiny simple setae at tip each.

Uropod 2: ( Fig. 20 j) peduncle shorter than outer ramous (0.83 ramous length); inner ramous slightly shorter than outer, with numerous simple cuspidate setae along outer margin; uropod 2 shorter than uropod 1.

Uropod 3: ( Fig. 20 i) peduncle shorter than peduncle of uropod 1, with few clusters of simple cuspidate setae at the apex; elongate 2-articulate outer ramus (6 times the length of inner ramus, 1.6 times as long as peduncle), with 5 tufts of strong cuspidate setae along the anterior margin and with 4 tufts of strong cuspidate setae along the posterior margin of article 1, article 2 minute, slightly shorter than crowning setae; inner ramous short and ovoid with two cuspidate seta subapically.

Telson: ( Fig. 20 k) fully cleft; lobes diverging distally; proximal notch positioned medially; tips of lobes acute, with one distal lateral and two dital medial strong cuspidate setae each.

Female (7.5 mm). Setation of cuticle as in male ( Fig. 23 d, e, f). Pereon segments smooth dorsally. Pleon segment 1 without teeth; pleon segment 2 with small central tooth; pleon segment 3 with very small central tooth. Urosome segment 1 with large tooth pulled back; urosome segment 2 with two pairs of small teeth and with single cuspidate seta among each lateral pair.

Head: similar to that of male.

Antenna 1: ( Fig. 21 a), slender; flagellum 0.9 times the length of peduncle, 17 articles; peduncle article 1 about 1.2 times as long and double the width of article 2, with two strong simple setae along lower margin, and with acute short protrusion at the outer surface of distal margin, article 3 1/3 of article 2 length; accessory flagellum 3- articulate.

Antenna 2: ( Fig. 21 b) similar to that in male; flagellum 6 articles; peduncle article 5 subequal in length to article 4, articles 1 + 2 + 3 shorter than article 5, article 1 with upper and lower protruding lobes reaching the 0.3 of article 3, article 3 with short protruding lobe.

Pereopod 2 (gnathopod 2): ( Fig. 21 f, g) with sexual dimorphism; coxa with subparallel anterior and posterior margins, with postero-distal denticle, front angle pointed, anterior margin unclear serrated; basis straight, longer than coxa, with a row of long simple setae along posterior margin and with more rare setae along anterior margin; merus subrectangular with distinct acute protrusion at the posterior distal corner, with two tufts of simple setae at the posterior margin and with a row of long setae at the distal-posterior corner; carpus long-triangular, slightly shorter than propodus, with 6 clusters of long setae along posterior margin; propodus with parallel anterior and posterior margins, palm oblique, with recess in the posterior part and with distinct postero-distal tooth, anterior margin lined with 8 groups of long setae, posterior margin with 8 tufts of serrate setae, palm with rare short setae and with a row of long serrate setae in the palmar recess; dactylus as long as palm, curved to the inside of propodus, outer margin strongly setose, tip of dactylus with acute nail.

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

Uropod 1: ( Fig. 23 a) peduncle with strong and curved interramal spur; rami subequal in length, subequal to peduncle length; peduncle and rami with tiny simple setae along outer edge, both rami with few tiny cuspidate setae at tip.

Uropod 2: ( Fig. 23 b) peduncle shorter than outer ramus (0.67 ramus length); inner ramous slightly shorter than outer, with 4–5 simple cuspidate setae along outer margin; uropod 2 shorter than uropod 1.

Variations. In specimens from Kashevarova shoal (57°32'N 143°47'E) dorsal teeth on pleon segments 2 and 3 are absent ( Fig. 30 d).

Etymology. Species name serraticoxae based on a Latin words “ serratis ” (serrated) and “coxa”, that is caused by shape of coxal plates: with a serrated front edge.

Ecology: Q. serraticoxae was found between 100–300 m on the silt-sand bottom with a constant low temperature (-1.2–0.5°C).

Distribution: The shelf of Sakhalin Island, Okhotsk Sea.

Remarks. Quasimelita serraticoxae sp. nov. differs from other Quasimelita species by the truncated anterior head lobe; by the ledged arrangement of the lower margins of coxal plates 1–4, by the serrated front edge of coxal plates 1–4 with pointed anterodistal angle. It differs from Q. jarettii sp. nov. and Q. quadrispinosa in the shape of telson with acute tips of lobes.

Figures

FIGURE 1. Distribution of Quasimelita species on the shelf of Sakhalin Island and nearest area.

FIGURE 16. Quasimelita serraticoxae sp. nov., holotype, male: a—lateral view, b—carination of body, c—cephalon, d—antenna 1, e—antenna 2, f—typical body sensible seta: a, d, e— 2 mm; c— 0.2 mm.

FIGURE 17. Quasimelita serraticoxae sp. nov., holotype, male: a, b, c—left mandible, d, e, f—right mandible, g—lower lips, h, i – maxilla 1; scale: a, d, g, h, i— 0.1 mm.

FIGURE 18. Quasimelita serraticoxae sp. nov., holotype, male: a—maxilla 2, b—maxilliped, c—pereopod 1, d—pereopod 2; scale: a, b— 0.1 mm; c, d— 1 mm.

FIGURE 19. Quasimelita serraticoxae sp. nov., holotype, male: a—pereopod 3, b—pereopod 4, c—pereopod 5, d—pereopod 6, e—pereopod 7; scale— 1 mm.

FIGURE 20. Quasimelita serraticoxae sp. nov., holotype, male: a—epimer 1 – 3, b—pleopod 2, с—coupling spines of pleopod 2, d—coupling spines of pleopod 3, e, f, g—coupling setae of pleopods 1, 2 and 3, h—uropod 1, i—uropod 2, j—uropod 3, k—telson; scale: a, b, h, i— 1 mm; c, d, e, f, g, k— 0.1 mm; j— 0.5 mm.

FIGURE 21. Quasimelita serraticoxae sp. nov., paratype, female: a—antenna 1, b—antenna 2, c—coxa 1, d—pereopod 1, e—field of scraping setae of merus of pereopod 1, f—pereopod 2, g—coxal gill of pereopod 2; scale: a, b, c, d, f, g— 1 mm.

FIGURE 22. Quasimelita serraticoxae sp. nov., paratype, female: a—pereopod 3, b—pereopod 4, c—pereopod 5, d—pereopod 6, e—pereopod 7; scale— 1 mm.

FIGURE 23. Quasimelita serraticoxae sp. nov., paratype, female: a—uropod 1, b—uropod 2, с—telson, d, e, f—specific sensible setae of body surface; scale: a, b— 1 mm; c— 0.1 mm.

FIGURE 30. Dorsal carination of new species of genera Quasimelita and Melitoides: a— Quasimelita tolyza sp. nov., male, shelf of north-eastern Sakhalin, b— Quasimelita jarettii sp. nov., male, Chikhacheva Bay, Japan Sea, c— Quasimelita serraticoxae sp. nov., male, shelf of north-eastern Sakhalin, d— Quasimelita serraticoxae sp. nov., male, Kashevarova shoal, e— Melitoides kawaii sp. nov., male, shelf of north-eastern Sakhalin; scale: 1 mm.