Abludomelita rotundactyla ( Ren, 2012 )

Labay, Vjacheslav S., 2016, Review of amphipods of the Melita group (Amphipoda: Melitidae) from the coastal waters of Sakhalin Island (Far East of Russia). III. Genera Abludomelita Karaman, 1981 and Melita Leach, 1814, Zootaxa 4156 (1), pp. 1-73 : 21-28

Abludomelita rotundactyla ( Ren, 2012)

Figures 2–7 , 28 a

Melita rotundactyla Ren, 2012: 289 –291, fig. 127.

Megamoera aequidentata Labay, 2013: 94 –100, figs. 23–26, 34.

Diagnosis. Pleon segment 1 dorsally with posterior row of 6–7 subequal teeth; pleon segment 2 dorsally with posterior row of 9–10 subequal teeth; pleon segment 3 with posterior row of 8–9 subequal teeth. Urosome segment 1 with central tooth and with 2 lateral teeth on each side; urosome 2 with 2 pairs of short teeth and with single strong cuspidate seta among them. Anterior head lobe shallow, lower margin with prominent accessory process. Maxilla 1, palp segment 1 with 2–4 lateral setae. Maxilla 2, inner plate, facial setae developed, submarginal in position. Propodus of pereopod 1 (male) long suboval, palm oblique rounded. Propodus of pereopod 2 (male) big, dactylus heavy, short, extended distally, with obtuse tip, anterior margin of dactylus rarely setose; palm oblique, with low irregular hinge tooth at anterior half and with postero-distal tooth. Uropod 3, proximal segment of outer ramus slender, with 4 clusters of marginal cuspidate setae at each margin. Telson lobes, proximal subapical notch more on outer margin.

Type material. Paratype male, 11 mm, X 44081 /Cr-1656, Aniva Bay (Sea of Okhotsk) (46°16'40''N; 142°28'20''E, 57 m), silt, Polupanov P.V., May 2013 . Paratypes: 4 males, X 44082 /Cr-1657; 4 females, X 44083 /Cr- 1658 with same data ; 1 male, X 44084 /Cr-1659, cape Junona , Aniva Bay (Sea of Okhotsk), mariculture collector installations, 6 m, gravel, D.A. Galanin , 5 females, X 44085 /Cr-1660 with same data .

Description. Male (11 mm). Medium size species. Vital body color is light-brown. Thoracic segments smooth dorsally ( Fig. 3 a, b, 28a). Pleon segment 1 with 7 denticles; pleon segment 2 with 9 denticles; pleon segment 3 with posterior row of 9 subequal denticles. Urosome segment 1 with central tooth and with 2 lateral teeth on each side; urosome 2 with 2 lateral pairs of teeth and with the simple cuspidate seta in the each pair.

Head: ( Fig. 3 c) slightly shorter than pereonites 1 and 2 together, with an indistinct rostrum; eyes small suboval; anterior head lobe large rounded; lower margin with a short notch.

Antenna 1: ( Fig. 4 a) 64% of body length, slender; flagellum slightly longer than peduncle, 32–33 articles, few very thin and short setae scattered along flagellum; peduncle article 1 double width but shorter length to article 2, article 3 0.3 of article 2 length; accessory flagellum 6-articulate.

Antenna 2: ( Fig. 4 b) flagellum almost 0.5 times as long as peduncle, 13–14 articles, bundle of thin setae on each article; peduncle articles 5 shorter than article 4, articles 1 + 2 + 3 0.66 times as long as article 5, articles 2 with protruding lobe reaching 2/3 the length of next article, articles 3 with short protruding lobe, articles 4 and 5 with numerous tufts of thin setae spaced evenly along the article.

Mouthparts as in female ( Labay 2013).

Mandible: ( Fig. 4 c) palp segment 2 rarely setose, palp segment 3 setose, 1-st article with protruding lobe, the percentage of total length of the articles of the palp 13% (article 1), 38% (article 2) and 49% (article 3).

Maxilla 1: ( Fig. 4 d) inner plate rounded-triangulate, lined with a row of setae (16–17 setae); palp segment 1 with 4 lateral setae.

Pereopod 1 (gnathopod 1): ( Fig. 5 a, b) coxa extended distally, width equal to length, with rounded anterior corner; basis straight with a rare row of short simple setae at the distal part of anterior margin and with several long setae at the posterior margin; ischium with one tuft of long setae at the postero-distal corner; merus subrectangular, with a row of simple setae along distal margin and with a cushion of short setae at the posterior margin; carpus long, 1.2 times as long as propodus, 6 oblique rows of long setae along outer posterior margin, with rows of long setae along anterior and posterior parts of distal margin and tomentose at the anterior-distal corner; propodus suboval, with 6 groups of long setae along posterior margin, with 3 tufts of long simple setae along anterior margin and with a dense bunch of long simple setae at the anterior distal corner, palm oblique, through an obtuse angle passes in posterior margin, minutely serrate with a row of numerous short stout simple setae, outer surface with a transverse row of long setae distally; dactylus as long as palm, with nail and with tooth-like protrusion above it.

Pereopod 2 (gnathopod 2) with sexual dimorphism: ( Fig. 5 c, d, e, 6a) coxa rounded distally, slightly narrowing distally, gills broad, with indistinct peduncle; basis slightly expands medially and distally, 1.1 times as long as coxa, with a few short simple setae along posterior margin and with a rare row of short setae along anterior margin; merus subrectangular with small acute protrusion at the posterior distal corner; carpus is short, triangular, with narrow posterior lobe, 5.3 times shorter than propodus; propodus very big, heavy, the width as length, palm oblique, with two double strong teeth at the anterior part of palm, palmar corner with strong tooth, with small strong simple setae along the palmar margin, anterior margin lined with 6 groups of setae, posterior margin with 9 tufts of setae; dactylus heavy, short, 0.6 times as long as palmar margin, extended distally, with obtuse tip, anterior margin of dactylus rarely setose.

Pereopod 3: ( Fig. 6 b) coxa slightly longer than coxa 2, rounded distally; basis sublinear with few minute setae along anterior margin and with rare long simple setae along posterior margin; merus long with 2–3 strong simple setae along anterior margin and with a single cluster from one strong simple seta and few thin setae at the anterior distal corner, posterior margin with 2–3 tufts of thin setae, posterior distal corner with a bunch of thin setae; carpus slightly shorter than merus, with 4–5 groups of strong cuspidate setae along posterior margin; propodus linear, more narrow and as long as carpus, with 5 groups of short strong simple setae along posterior margin; dactylus medium size (0.4 times as long as propodus), with nail.

Pereopod 4: ( Fig. 6 c) coxa subequal in length to coxa 3, anterior and posterior corners rounded, posteriorly excavated; segments 2–7 similar to as in pereopod 3.

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

Pereopod 5: ( Fig. 6 d) coxa with slightly rounded front margin, with rounded hind margin and with rounded anterior lobe pulled down and back; basis regular, with posterior wing, width 0.65 times as long, posterior distal corner rounded, posterior margin crenulated, anterior margin with small stout setae; merus slightly broaded medially, with 2 groups of short setae along anterior margin, with 3 short stout setae along posterior margin, with 2 strong stout setae at the posterior distal corner; carpus 0.8 times as long as merus, with the single strong 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 1.3 times as long as carpus, with 2 bunches of cuspidate setae along anterior margin; dactylus small (0.33 times length of propodus), with nail.

Pereopod 6: ( Fig. 6 e) coxa with slightly rounded hind margin, posterior corner obtuse, anterior lobe pulled back and down, front margin rounded, with short simple setae; basis regular, with narrow posterior wing, width 0.59 times as long, posterior distal corner rounded, hind margin crenulated, anterior margin with small stout setae; merus long, with 2 groups of stout simple setae along anterior margin and with 3 groups of same setae along posterior margin, and with clusters of 2 strong stout setae at anterior and posterior distal corners each; carpus 0.79 times as long as merus, with the single group of 2 cuspidate 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 1.3 times as long as carpus, with 3 clusters of short cuspidate setae along anterior margin; dactylus small (0.3 times as long as propodus), with nail.

Pereopod 7: ( Fig. 7 a) coxa small, without distinct anterior lobe and with triangulate posterior lobe; basis regular, with rounded posterior wing, broaded medially, width 0.69 times of length, posterior distal corner rounded, posterior margin crenulated, anterior margin with small cuspidate setae; merus long, with 2 groups of stout simple setae along anterior margin and with 3 groups of same setae along posterior margin, and with single cluster of 3–4 strong stout setae at anterior and posterior distal corners each; carpus 0.88 times as long as merus, with the single cuspidate seta 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 1.4 times as long as carpus, with 3 clusters of cuspidate setae along anterior margin, anterior distal corner with a crown of long cuspidate setae; dactylus small (0.3 times as long as propodus), with nail.

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

Epimeral plates: ( Fig. 7 b) plate 1 with oblique crest, posterior margin rounded, with 4 notches, lower margin with 2 strong simple setae, hind corner with a notch; plate 2 with oblique crest, posterior margin straight, ventral margins convex, with a row of 6 strong simple setae; plate 3 hind corner produced, acute, posterior margin concave, notched, ventral margin with a row of 10 strong simple setae.

Pleopods: ( Fig. 7 c–g) normal, no sexual dimorphism; peduncle with two specific toothed coupling setae on the inner corner; coupling basis of inner ramus with 3–4 of specific stout two-pointed cuspidate setae along inner margin: pleopod 1 (4), pleopod 2 (4), pleopod 3 (3).

Uropod 1: ( Fig. 7 h) peduncle with strong interramal spur; rami subequal in length, 0.9 times as long as peduncle; peduncle and rami with tiny simple setae along outer edge, both rami with few tiny simple setae at the tip.

Uropod 2: ( Fig. 7 i) peduncle shorter than outer ramus (0.8 ramus length); inner ramus shorter than outer, with numerous simple cuspidate setae along outer margin; uropod 2 shorter than uropod 1.

Uropod 3: ( Fig. 7 j) long, 1.15 times as long as uropod 1; peduncle shorter than peduncle of uropod 1, with two cuspidate setae at the anterior margin, with two clusters of simple cuspidate setae at the apex; elongate 2-articulate outer ramus (6.4 times length of inner ramus) 2.3 times as long as peduncle, with 4–5 tufts of small simple stout setae along anterior and posterior margins of article 1 each, article 2 minute, more than 10 times shorter than article 1; inner ramous short and ovoid with two cuspidate setae at the tip.

Telson: ( Fig. 7 k) fully cleft; lobes diverging distally, proximal notch positioned laterally; apical and subapical simple cuspidate setae long, lobes with single short cuspidate setae at the medial margin each.

Sexual dimorphism: Only in structure of pereopod 2. Pereopod 2 in male more bigger than in female ( Labay 2013: fig. 24h), with a heavy, short, extended distally dactylus.

Variations: Urosome 2 with or without strong cuspidate seta among lateral pair of dorsal teeth.

Ecology. A. rotundactyla was found in the depth interval 5–60 m on gravel and silt bottoms. Female with eggs in marsupium was found in October.

Distribution. Aniva Bay, Okhotsk Sea (Sakhalin Island); Japan Sea ( Fig. 2 ).

Remarks. A. rotundactyla was described by Ren (2012) from coastal waters of China (Japan Sea) on a single male as the Melita rotundactyla Ren, 2012 .

This species also was described by Labay (2013) from Aniva Bay (Sea of Okhotsk) on a single female as the Megamoera aequidentata Labay, 2013 . Finding of new exemplars of this species from Aniva Bay allowed described the male and clarify the species features. By specific features of the structure (primarily of pereopod 2 of males) this species is listed to the genus Abludomelita . Description of the male from Aniva Bay is almost identical to the description of the male from coastal waters of China by Ren (2012). Therefore, I attribute the specimens from Aniva Bay to the species A. rotundactyla ( Ren, 2012) .

Figures

FIGURE 2. Distribution of Abludomelita species on the shelf of Sakhalin Island and nearest area.

FIGURE 3. Abludomelita rotundactyla (Ren, 2012), paratype, male: a—lateral view, b—carination of abdominal segments, c—cephalon; scale: a— 2 mm; b, c— 1 mm.

FIGURE 4. Abludomelita rotundactyla (Ren, 2012), paratype, male: a—antenna 1, b—antenna 2, c—left mandible, dmaxilla 1; scale: a, b— 1 mm; c, d— 0.1 mm.

FIGURE 5. Abludomelita rotundactyla (Ren, 2012), paratype, male: a—pereopod 1, b—propodus and dactylus of pereopod 1, inner side, c—pereopod 2, d—propodus and dactylus of pereopod 2, inner side, e—palmar angle of propodus of pereopod 2; scale— 1 mm.

FIGURE 6. Abludomelita rotundactyla (Ren, 2012), paratype, male: a—coxal gill 2, b—pereopod 3, c—pereopod 4, dpereopod 5, e—pereopod 6; scale— 1 mm.

FIGURE 7. Abludomelita rotundactyla (Ren, 2012), paratype, male: a—pereopod 7, b—epimers 1, 2, 3, c—pleopod 3, dcoupling spines of pleopod 3, e, f, g—coupling setae of pleopods 1, 2, 3, h—uropod 1, i—uropod 2, j—uropod 3, k—telson; scale: a, b, c, h, I, j, k— 1 mm; d – g— 0.1 mm.

FIGURE 28. Dorsal carination of new species and subspecies of genera Abludomelita and Melita: a— Abludomelita rotundactyla (Ren, 2012), paratype, male, b— Abludomelita klitinii sp. n., holotype, male (type locality), c— Abludomelita klitinii sp. n., paratype, male (Ptichje Lake), d— Abludomelita okhotensis sp. n., holotype, male, e— Melita shimizui sachalinensis ssp. n., paratype, female; scale— 1 mm.