Melitoides kawaii, 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 : 270-277

Melitoides kawaii sp. nov.

Figures 24–29 , 30 e

Diagnosis. Pereon segments without dorsal teeth and denticles. Pleon segment 1 smooth; pleon 2–3 moderately mid-dorsally toothed or humped. Urosome segments 1 & 2 mid-dorsally toothed. Inferior antennal sinus shallow, cusp regressed. Eye small, indistinct, with a few ommatidia. Antenna 1 medium, peduncular segment 3 relatively short; accessory flagellum 4-segmented; flagellum short (22+ segments). Antenna 2, peduncle 3 short; flagellum longer than peduncle 5, 10-segmented. Telson lobes appearing fused basally, apices each with single short strong seta. Maxilla 2, inner plate, facial setae row not reduced, submarginal. Maxilliped, inner plate not exceeding the distal margin of palp segment 2. Coxae 2–4 deeper than broad. Pereopod 2 (male), propodus, anterior and posterior margins subparallel, palm nearly perpendicular, anterior margin of dactyl rarely setose. Pereopods 6–7 elongate. Pereopods 5–6, bases broad. Pereopod 7 base ralatively narrow, weakly broadened proximally.

Pleon 3 rounded. Uropod 3, terminal segment of outer ramus small, shorter than associated setae, margins of first segment of outer ramus with 2–4 clusters of short setae.

Female undescribed.

Type material. Holotype male, 10 mm, 41811/Cr-1516, north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (52°08'49"N, 143°53'88"E, 60 m), sand, V.Iu. Lalov, September 2012. Paratypes: 3 males, 41812/ Cr-1517 with same data as holotype.

Type locality. north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (52°08'49"N, 143°53'88"E, 60 m).

Description. Male (10 mm). Medium size species. Vital body color unknown. Pereon segments without teeth and humps ( Fig. 25 a, b, 30d). Pleon segment 1 without teeth and humps; pleon segments 2 & 3 with mid-dorsal tooth each. Urosome segments 1 & 2 with medial-dorsal tooth protruding vertically.

Head: ( Fig. 25 a, c) slightly shorter than pereonites 1 and 2 together with an indistinct rostrum; eyes small oval, light colored; inferior antennal sinus shallow, cusp regressed.

Antenna 1: ( Fig. 25 d) 0.4 times of body length, slender; flagellum exceeding 1.5 times the length of the peduncle, 22–23 articles, few very thin and short setae scattered along flagellum; peduncle article 1 double width and slightly longer length than article 2, article 3 0.4 times the length of article 2; accessory flagellum 4-articulate.

Antenna 2: ( Fig. 25 e) flagellum almost 0.6 times as long as peduncle, 10 articles, bundle of thin setae on each article; peduncle article 5 slightly shorter than article 4, articles 1 + 2 + 3 subequal to article 5, articles 2 with protruding lobe almost reaching the distal end of next article.

Mouthparts.

Labrum: ( Fig. 25 f) short and rounded, frontal margin slightly concave medially, densely covered by minute setae.

Mandible: ( Fig. 26 a–f) incisor crenulate and stretching in a rounded tip; setae stout and serrate, numerous (10+), as long as incisor; molar cylindrical triturative, chewing plate flattened; palp 3-articulate, palp segments 2 and 3 poorly setose, article 1 without protruding lobe, the percentage of total length of the articles of the palp are 19% (article 1), 40% (article 2), 41% (article 3).

Labium: ( Fig. 26 g) inner lobes large, well defined, rounded; outer lobes rounded at distal margin.

Maxilla 1: ( Fig. 26 h) inner plate subtriangular, lined with a row of simple setae (more than 10); outer plate elongate, 1.5 as long as inner plate, apically with 2 rows of 9 toothed strong setae; palp 2-articulate, article 2 2 times as long as article 1, article 2 apically with two rows of 11–12 cuspidate setae each.

Maxilla 2: (Fig. 27a) inner plate shorter than outer plate, facial row of setae of inner plate produced, not reduced, closely submarginal, tip covered with numerous simple setae; outer plate with same numerous of simple setae.

Maxilliped: (Fig. 27b) compact; inner plates medium, fully cleft, distal margin with a row of 3 teeth, inner and distal margins with long plumose setae; outer plates reaching 0.8 of palp article 2, inner margin lined with a row of short stout teeth-like setae longer toward the apex, apical row with long thin plumose setae; palp 4-articulate, the percentage of total length of the articles of the palp are 18% (article 1), 47% (article 2), 20% (article 3), 15 (article 4), article 2 with numerouse setae along inner margin; article 3 bilobed, tip of article 3 with a row of simple setae along apical indentation; article 4 bent, inner margin with a line of serrate setae, inner surface with a dense row of tiny setae.

Pereopod 1: (Fig. 27c, d) coxa medium long, extended and rounded anterior-distally; basis straight with a rare row of long simple setae along distal part of anterior margin and with long setae along the posterior margin; ischium subrectangular with a bunch of long simple setae at the postero-distal corner; merus subrectangular, with dense group of short setae along distal part of posterior margin, distal margin with a row of long serrate setae; carpus long and broad, 1.3 times as long as propodus, 6–7 oblique rows of long plumose setae along outer posterior margin, 4 transverse rows of long plumose setae along anterior margin, with a row of long plumose setae along anterior and posterior parts of distal margin, inner surface with three transverse rows of long setae; propodus with subparallel anterior and posterior margins, with 4 oblique groups of long plumose setae along posterior margin, with 5 tufts of long setae along the anterior margin and with a dense bunch of long simple setae at the anterior distal corner, palmar margin slightly oblique, concave, with a row of short thin simple setae along palmar margin and with a row of cuspidate setae near the postero-distal corner; dactylus as long as palm, curved.

Pereopod 2: (Fig. 27e, f) coxa long, subrounded distally; basis substraight, shorter than coxa, with long simple setae along posterior margin and with few rare short setae along anterior margin; merus subrectangular with short triangular protrusion at the posterior distal corner, carpus cup-shaped, with developed posterior lobe, almost 3 times shorter than propodus; propodus subrectangular, palm subperpendicular, with distinct postero-distal tooth and with two large and one small obtuse palmar teeth, posterior margin with rare setae, palm with rare small cuspidate setae; dactylus as long as palm, curved to the inside of propodus, outer margin rarely setose, with nail.

Pereopod 3: ( Fig. 28 a) coxa slightly longer than coxa 2, with rounded anterior and posterior corners; basis long, anterior margin concave, posterior margin convex, with long simple setae along posterior margin; merus long; carpus 0.66 times as long as merus, with 3 cuspidate setae along posterior margin; propodus linear, more narrow and slightly longer than carpus, with 2 small setae along posterior margin; dactylus medium (0.42 of propodus), with nail.

Pereopod 4: ( Fig. 28 b) coxa as long as coxa 3, slightly excavated posteriorly, leg is similar to that of the pereopod 3.

Pereopods 5–7 elongated from pereopod 5 to pereopod 6, pereopod 6 subequal to pereopod 7.

Pereopod 5: ( Fig. 28 c) coxa rounded anteriorly and with anterior lobe pulled back and down, hind margin with rounded posterior lobe; basis short and broad, with rounded posterior wing, slightly narrowed distally, width 0.78 times the length, hind margin crenulated, anterior margin with short cuspidate setae; merus slightly broad medially, with one cuspidate seta at the posterior margin and with one cluster of small setae in the middle of anterior margin, and with a cluster of two-three cuspidate setae at the posterior distal and anterior distal corners each; carpus subequal to merus in length, with 2 groups of 2 cuspidate setae at the anterior margin and with single clusters of cuspidate setae at the anterior and posterior distal corners each; propodus linear, more narrow than carpus and subequal to carpus length; dactylus small (1/4 of propodus), with nail.

Pereopod 6: ( Fig. 28 d) coxa with quadrate hind margin and with long and narrow anterior lobe pulled down; basis short, with weak posterior wing, narrowed distally, width 0.58 times as long, posterior distal corner rounded, hind margin crenulated, anterior margin with small cuspidate setae; merus long, with 2 short cuspidate setae along anterior and posterior margins each, and with single clusters of 2–3 cuspidate setae at anterior and posterior distal corners each; carpus as long as merus, with 5 rare cuspidate setae at the anterior margin and with a single cluster of cuspidate setae at the anterior and posterior distal corners each; propodus linear, more narrow and as long as carpus; dactylus small (0.29 times the length of propodus), with nail.

Pereopod 7: ( Fig. 28 e) coxa small, with weak triangular anterior lobe pulled down, without posterior lobe; basis narrow, slightly broadened posteriorly, width 0.5 times the length, posterior distal corner rectangular, hind margin crenulated, anterior margin with small cuspidate setae in the distal half; merus long, slightly broadened medially, with 2 clusters of small cuspidate setae along anterior and posterior margins, and with single clusters of 1–2 cuspidate setae at anterior and posterior distal corners each; carpus 1.2 times as long as merus, with 4 groups of cuspidate setae along the anterior margin and with a single clusters of cuspidate setae at the anterior and posterior distal corners each; propodus linear, more narrow and as long as carpus, with 6 groups of short cuspidate setae along anterior margin; dactylus small (0.25 times the length of propodus), with nail.

Coxal gills 2–6. Coxal gills 5 and 6 distinctly smaller than gills 2–4.

Epimeral plates: ( Fig. 25 a, b) plates 1–3, hind corner not acuminate, rounded postero-distally, plates 1 and 2 with oblique crest, lower margins not serrate, without setae.

Pleopods: ( Fig. 28 f, g) normal; peduncle with two specific toothed coupling strong setae on the inner corner; coupling basis of inner ramus with 2–4 specific stout two-pointed plumose setae along inner margin. Uropod 1: ( Fig. 29 a) peduncle without interramal spur, armed with numerous tiny cuspidate setae along inner and outer margins; rami subequal in length, shorter than peduncle length; rami with tiny simple setae along outer edge, both rami with few tiny simple setae at tip.

Uropod 2: ( Fig. 29 b) peduncle shorter than outer ramus (0.72 ramus length); inner ramus slightly shorter than outer, both with numerous simple cuspidate setae along outer margin; uropod 2 1.5 times shorter than uropod 1.

Uropod 3: ( Fig. 29 c) peduncle shorter than peduncle of uropod 2, with a single cuspidate seta at the distal margin; elongate 2-articulate outer ramus (8 times the length of inner ramus), with 2 tufts of small cuspidate setae along anterior margin, and with 4 tufts of cuspidate setae along posterior margin of article 1, article 2 minutely, 5 times shorter than crowning setae, 13 times shorter than article 1; inner ramous short and round with one cuspidate seta subapically.

Telson: ( Fig. 29 d) fully cleft, lyre-shaped; lobes diverging distally, without subapical notches, with single apical simple cuspidate seta each.

Female unknown.

Etymology. Named in honor of Tadashi Kawai—Japanese reasercher of Crustacea.

Ecology: Melitoides kawaii was found at a depth of 60 m on the sand bottom.

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

Remarks. Melitoides kawaii sp. nov. differs from Melitoides makarovi Gurjanova, 1934 by the presence of eye, by the presence of second article of outer ramus of uropod 3, by the form of basis of pereopod 7 (in M. makarovi basis of pereopod 7 broad; in M. kawaii basis narrowed), by the armament of palmar margin of propodus of pereopod 2 (in M. makarovi palmar margin with two bicuspid processes; in M. kawaii palmar margin with two distinct and one indistinct obtuse teeth).

Figures

FIGURE 24. Distribution of Melitoides species on the shelf of Sakhalin Island and nearest area.

FIGURE 25. Melitoides kawaii sp. nov., holotype, male: a—lateral view, b—carination of body, c—cephalon, d—antenna 1, e—antenna 2, f—upper lip: scale: a— 2 mm; b, c— 0.5 mm; d, e— 1 mm; f— 0.1 mm.

FIGURE 26. Melitoides kawaii sp. nov., holotype, male: a, b, c—left mandible, d, e, f—right mandible, g—lower lips, h—maxilla 1; scale— 0.1 mm.

FIGURE 28. Melitoides kawaii sp. nov., holotype, male: a—pereopod 3, b—pereopod 4, c—pereopod 5, d—pereopod 6, e—pereopod 7, f—pleopod 3, g—coupling spines of pleopod 3; scale: a – f— 1 mm, g— 0.1 mm.

FIGURE 29. Melitoides kawaii sp. nov., holotype, male: a—uropod 1, b—uropod 2, c—uropod 3, d—telson; scale: a – c— 1 mm; d— 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.