Quasimelita tolyza, 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 : 242-250

Quasimelita tolyza sp. nov.

Figures 1 –8, 30a

Diagnosis. Anterior head lobe large, rounded, lower margin with a short notch. Eye small, oval. Pleon segments 1–3 with central tooth and 1 lateral denticle on each side. Urosome segment 1 with central tooth and 1 lateral denticle on each side; urosome 2 with 2 pairs of short teeth, with single cuspidate seta among each lateral pair. Maxilla 1, inner plate with numerous marginal setae; palp segment 1 with 7 lateral setae. Maxilla 2, facial setae of inner plate not reduced (19–20 setae), distally medial, closely submarginal. Coxa 1 without acute anterior corner; margins of all coxae without distinct serrations. Coxal plates 1 and 2 longer than plates 3 and 4. Propodus of pereopod 1 (male) relatively small, shorter than carpus, oval, palm indistinct, without distinct palmar angle. Pereopod 2 (male), anterior margin of dactyl strongly setose; palm oblique, strongly convex, with large tooth on the palmar corner. Basis of pereopod 7 with poorly developed and slightly rounded posterior lobe, narrowed distally. Uropod 3 long; peduncle 2 times shorter than outer ramous; proximal segment of outer ramous slender, tapering distally, with 5 clusters of marginal stout simple setae; terminal segment distinct, small. Tips of telson lobes acute, proximal subapical notch more on outer margin.

Type material. Holotype male, 25 mm, 41799/Cr-1504, north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (51°16'11"N 144°12'46"E, 159 m), silt, 17 June 2013. Paratypes: 1 male, 24 mm, 41800/Cr-1505; with same data as holotype; 1 male, 12 mm, 41801/Cr-1506, the north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (51°16'14''N, 144°12'46''E, 161 m), silt, I.N. Moukhametov.

Type locality. The north-east shelf of Sakhalin Island, Okhotsk Sea, Far East of Russia (51°16'11"N 144°12'46"E, 160 m).

Description. Male (25 mm). Vital body color is grey-olive. Thoracic segments smooth dorsally ( Fig. 2 a, b). Pleon segments with large central tooth and two small lateral teeth each. Urosome segment 1 with large central tooth and two small lateral teeth; urosome segment 2 with two pairs of small teeth and with single cuspidate seta among each lateral pair. Body surface with rare specificl sensible setae: ( Fig. 7 f) from the top of the stalk tillering diverge few simple long branches.

Head: ( Fig. 2 c) slightly shorter than pereonites 1 and 2 together, with an indistinct rostrum; eyes small oval; anterior head lobe large rounded; lower margin with a short notch.

Antenna 1: ( Fig. 2 d, f, g) nearly 70% of body length, slender; flagellum exceeding 1.5 times the length of peduncle, 49 articles, few very thin setae scattered along the flagellum; peduncle article 1 double the width and subequal in length to article 2, with 4 stout simple setae along posterior margin and with acute tooth on the distal end of both the outer and inner surfaces, article 3 33% the length of article 2; accessory flagellum 6-articulate.

Antenna 2: ( Fig. 2 e, h, I, j) flagellum nearly 43% the length of the peduncle, 16–17 articles, with a crown of few thin setae on each article; peduncle article 5 slightly shorter than article 4, articles 1, 2, 3 together shorter than article 4 or article 5; article 1 with protruding lobe reaching the middle of the article 3 in the posterior margin and with protruding lobe in the inner margin of distal end ( Fig. 2 h); article 3 with acute tooth in the distal end of outer surface, article 4 with acute tooth in the distal end of inner surface ( Fig. 2 i), articles 4 and 5 with numerous evenly spaced tufts of thin setae.

Mouthparts.

Labrum: ( Fig. 3 h) frontal margin slightly concave medially, densely covered by minute setae.

Mandible: ( Fig. 3 a–g) incisor crenulate and stretching in a rounded tip; raker setae stout subplumose, numerous (13+), equal to incisor in length; molar flattened triturative, protrusion with developed triturative area (additional molar) located near the base of palp; palp 3-articulate, palp segment 2 with a rare row of 4 simple setae and with a distal bunch of simple setae along the lower margin, segment 3 with a rare row of 4 simple setae along the lower margin and with two simple setae apically, 1-st article with indistinct protruding lobe, the percentage of total length of the articles of the palp 15% (article 1), 42% (article 2) and 43% (article 3).

Labium: ( Fig. 4 a) inner lobes small but well defined, rounded; outer lobes semi-square / rounded at distal margin, densely covered by minute setae.

Maxilla 1: ( Fig. 4 b) inner plate suboval, lined with a row of numerous simple setae (more then 20 setae); outer plate elongate, 1.7–1.8 times as long as the inner plate, apically with 2 rows of 9 comblike strong setae; palp 2- articulate, article 2 1.8 times as long as article 1, article 1 with a tuft of 6–7 long simple setae, article 2 apically with a row of simple stout setae and with an additional row of thin simple setae.

Maxilla 2: ( Fig. 4 c) inner plate slightly shorter than outer plate, facial setae of inner plate numerouse (more than 20), distal, closely submarginal, tip covered with numerous simple setae; outer plate with numerous simple setae on the tip, subapically with the row of 10–12 setae.

Maxilliped: ( Fig. 4 d) inner plates large, fully cleft, distal margin with a row of 3 teeth, inner margin with long plumose setae (8–10 setae); outer plates reaching of 2/3 of palp article 2 length, inner margin lined with a row of short stout teethlike spines longer toward the apex, smoothly into the apical row of long thin setae; palp 4- articulate, the percentage of total length of the articles of the palp are 13% (article 1), 43% (article 2), 27% (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 and with a subapical tuft of long setae; article 4 inner margin with a line of serrate setae (Watling type IV.1) ( Watling 1989).

Pereopod 1 (gnathopod 1): ( Fig. 4 e, f, 5) coxa extended distally, with rounded anterior corner, with a small hook at the posterior angle; basis substraight, slightly narrowed proximally, front edge with longitudinal groove, anterior margin with bunches of long setae along distal half, posterior margin with a row of long setae; merus subrectangular, with a row of simple setae along distal margin and with a transverse subdistal cushion of short setae at the inner surface; carpus long, 1.2 times as long as propodus, 12–13 oblique rows of long serrate setae along posterior margin, 5 oblique rows of long serrate setae along anterior margin, with 4 transverse rows of long setae on the inner surface near the posterior margin, with a row of long setae along anterior part of distal margin and tomentose at the anterior-distal corner; propodus suboval, with numerous groups of long serrate setae along posterior margin, with 6 transverse rows of long setae along anterior margin and with a dense bunch of long simple setae at the anterior distal corner, palmar margin convex, smoothly into the posterior margin, demarcated from the last by small tooth, inner surface with two groups of setae along palmar margin, with small tooth near palmar corner and with three groups of long setae along posterior margin, outer surface with one transverse row of long setae distally; dactylus as long as palm, with nail.

Pereopod 2 (gnathopod 2): ( Fig. 6 a–c) coxa subquadrate; basis straight, two times as long as coxa, anterior margin with longitudinal groove, with long simple setae along posterior margin and with numerous long setae along distal part of anterior margin; merus subrectangular with acute protrusion at the posterior distal corner, with a few simple setae along posterior margin, with a row of long setae at the inner surface subdistally; carpus triangular, 2.2 times shorter than propodus, with numerous setae along posterior margin and with 6 tufts of long setae along anterior margin; propodus extended medially, palm oblique and convex, with numerous tubercles and simple stout setae along the palmar margin, palmar corner with long thin acute tooth, anterior margin lined with numerous groups of setae, posterior margin with numerous tufts of serrate setae; dactylus as long as palm, slightly curved to the inside of propodus, outer margin strongly setose, tip of dactylus is acute.

Pereopod 3: ( Fig. 6 d) coxa shorter then coxa 2, subquadrate, posterior corner with small hook; basis linear with few short setae along anterior and posterior margins and with rare long simple setae in proximal half of posterior margin; merus long with 2 strong simple setae along anterior margin, posterior margin with three clusters of thin setae, anterior-distal angle with acute protrusion; carpus 0.75 times as long as merus, with 4 bunches of simple setae along posterior margin; propodus linear, more narrow and 0.8 as long as carpus, with 3 bunches of simple setae along posterior margin; dactylus long (1/2 of propodus), with nail.

Pereopod 4: ( Fig. 6 e, f) coxa as long as coxa 3 and 1.5 times as wide as coxa 3, subquadrate, posteriorly slightly excavated, posterior corner with small hook; leg is similar to that of the pereopod 3.

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

Pereopod 5: ( Fig. 7 a) coxa with rounded front margin, with quadrate hind margin and with narrowed anterior lobe pulled back and down; basis long, slightly narrowed distally, with weak posterior wing, width 0.35 times as long, hind margin crenulated, anterior margin with small short setae; ischium subquadratic, with small acute protrusion at the anterior-distal corner; merus slightly broaded medially, with two short stout setae at the middle of posterior margin, with 4 groups of short setae along anterior margin and with a few strong setae at anterior and posterior distal corners each; carpus 0.83 times as long as merus, with 3 groups of stout setae at the anterior margin and with a single cluster of strong stout setae at the anterior and posterior distal corners each; propodus linear, more narrow and as long as carpus, with 3 bunches of strong simple setae along anterior margin; dactylus small (0.28 times propodus length), bent, with nail.

Pereopod 6: ( Fig. 7 b, c) coxa with oblique anterior margin, with quadrate hind margin and with small narrow anterior lobe pulled back and down, front margin with two small cuspidate setae; basis narrow, with weak posterior wing, slightly narrowed distally, width 0.33 times as long, hind margin crenulated, anterior margin with small stout setae; merus long and narrow, with 3 short stout simple setae along posterior margin and with few thin simple setae along anterior margin, and with single clusters of 2–3 strong stout setae at anterior and posterior distal corners each; carpus as long as merus, with 3 groups of 1–3 strong stout setae at the anterior margin and with a single clusters of strong stout setae at the anterior and posterior distal corners each; propodus linear, as long as carpus, with 4 clusters of strong simple setae along anterior margin; dactylus medium (0.45 of propodus length), with nail.

Pereopod 7: ( Fig. 7 d, e) coxa small, without distinct anterior lobe and with rounded posterior lobe, front margin with two small cuspidate setae; basis regular, with weakly rounded posterior wing, narrowed distally, width 0.4 times length, hind margin crenulated, anterior margin with small setae; merus long, with 3 groups of stout simple setae along anterior and posterior margins each, and with single clusters of 2–3 strong stout setae at anterior and posterior distal corners each; carpus, propodus and dactylus similar to that in pereopod 6.

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

Epimeral plates: (Fig. 8a, b, c) hind corner acuminate; plate 1 rounded triangular, lower margin with one strong simple seta, hind corner slightly produced with small tooth; plate 2 ventral margin convex, with a row of 5 strong simple setae; plate 3 hind corner produced, rounded, posterior margin convex, ventral margin with a row of 7 strong simple setae.

Pleopods: (Fig. 8d, e, f) normal; peduncle with two specific toothed coupling setae on the inner corner; inner ramus longer than outer ramus, coupling basis of inner ramus with 3–5 of specific stout two-pointed plumose setae along inner margin.

Uropod 1: (Fig. 8g) peduncle with large distal spur on the outer margin and with small acute distal tooth on the inner margin, inner and outer margins lined with numerous short acute setae; rami subequal in length, slightly shorter than peduncle length, with tiny simple setae along outer edge, both rami with few tiny simple setae at the tip.

Uropod 2: (Fig. 8h) peduncle subequal to outer ramus, with acute interramal tooth; inner ramus shorter than outer; both rami with numerous simple cuspidate setae along outer margin; uropod 2 shorter than uropod 1.

Uropod 3: (Fig. 8i, j) long, subequal to uropod 1; peduncle shorter than peduncle of uropod 1, 0.46 as long as outer ramus, with two cuspidate setae along outer and inner margins each, with two clusters of simple cuspidate setae at the apex; elongate 2-articulate outer ramus (10 times length of inner ramus) with 5 tufts of small simple stout setae along the anterior margin and posterior margins of article 1 each, article 2 minutely, more than 16 times shorter than article 1; inner ramous short and ovoid with two various cuspidate setae subapically.

Telson: (Fig. 8k) fully cleft; lobes diverging distally, with acute tips; proximal notch positioned laterally; each lobe with one stout seta in the lateral notch, with two stout setae in the medial notch and with one stout seta toward the base.

Female. unknown.

Etymology. The species name tolyza derived from the Nivkh word Tol yz (a mythical spirit of marine animal).

Ecology. Q. tolyza was found between 159–161 m on silt bottom.

Distribution. The north-east shelf of Sakhalin Island, Okhotsk Sea.

Remarks. Quasimelita tolyza sp. nov. is most similar to Q. formosa . Q. tolyza differs from Q. formosa in the armament of dorsal surface of pleosome, in the shape of propodus of pereopod 2 and in the shape of basis of pereopod 7. In Q. tolyza dorsal surface of pleon segments 1–3 with one large central tooth and with two small lateral teeth; in Q. formosa pleon segment 1 without dorsal teeth, pleon segments 2 and 3 with one large dorsal tooth each. In Q. tolyza palmar angle of propodus of pereopod 2 with long thin acute spine; in Q. formosa palmar angle of propodus of pereopod 2 with short obtuse tooth armed by the row of long setae. Q. tolyza have a regular basis of pereopod 7, with weakly rounded posterior wing, narrowed distally; basis of pereopod 7 in Q. formosa linear, with straight posterior margin.

Figures

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

FIGURE 2. Quasimelita tolyza sp. nov., holotype, male: a—lateral view, b—carination of abdominal segments, c—cephalon, d—antenna 1, e—antenna 2, f—additional flagellum of antenna 1, g—articles of flagellum of antenna 1, h—peduncle articles 1 – 3 of antenna 2, inner side, i—peduncle article 4 of antenna 2, inner side, j—articles of flagellum of antenna 2; scale: b— 1 mm; c— 0.5 mm.

FIGURE 3. Quasimelita tolyza sp. nov., holotype, male: a, b, c—left mandible, d, e, f, g—right mandible, g—additional molar of right mandible, h—upper lip; scale: a, d, h— 1 mm.

FIGURE 4. Quasimelita tolyz sp. nov., holotype, male: a, — lower lips, b—maxilla 1, c—maxilla 2, d—maxilliped, e—pereopod 1, outer side, f—propodus of pereopod 1, outer side; scale: a— 0.2 mm; b— 0.5 mm, c— 0.3 mm, d— 1 mm.

FIGURE 6. Quasimelita tolyza sp. nov., holotype, male: a—pereopod 2, b—propodus of pereopod 2, inner side, c—merus and carpus of pereopod 2, inner side, d—pereopod 3, e—pereopod 4, f—carpus, propodus and dactylus of pereopod 4.

FIGURE 7. Quasimelita tolyza sp. nov., holotype, male: a—pereopod 5, b—coxa 6, c—pereopod 6, d—coxa 7, e—pereopod 7, f—sensible seta from body surface.