Abludomelita klitinii, Labay, Vjacheslav S., 2016

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 : 28-39

Abludomelita klitinii sp. nov.

Figures 2 , 8–15 , 28 b

Diagnosis. Pleon segments 1–2 with central tooth and 1–2 lateral denticles on each side; pleon segment 3 with posterior row of 6–7 denticles, central denticle subequal to neigbour denticles. Urosome segment 1 with central tooth and with 2 lateral teeth on each side; urosome 2 with 2 pairs of teeth and with strong seta in each lateral pair. Anterior head lobe shallow, lower margin with prominent accessory process. Maxilla 1, palp segment 1 with 4 lateral setae. Maxilla 2, inner plate, facial setae developed, submarginal in position. Propodus of pereopod 1 (male) long suboval, palm rounded, without distinct palmar angle. Pereopod 2 (male), dactylus inflated, with obtuse tip, anterior margin of dactylus rarely setose; palm oblique rounded, with low irregular hinge tooth and small posterodistal tooth. Uropod 3, proximal segment of outer ramus slender, with 5 clusters of marginal cuspidate setae at each margin. Telson lobes, proximal subapical notch more on outer margin.

Type material. Holotype male, 12 mm, X 44086 /Cr-1661, south-west shelf of Sakhalin Island, Tatar Strait , Sea of Japane, Far East of Russia (47°45'N 142°00'54"E, 20 m), sand and gravel, 30 May 2010, P.V. Polupanov . Paratypes: 1 female, 10.6 mm, X 44087 /Cr-1662; 8 males, X 44088 /Cr-1663; 29 females, X 44089 /Cr-1664; with same data as holotype ; 1 male, 11 mm, X 44090 /Cr-1665, the channel of the lagoon lake Ptichje , south-east Sakhalin, Far East of Russia (54T 697139, 5143045, plankton nets), 11 May 2012, V.S. Labay ; 2 males, X 44091 / Cr-1666; 7 females, X 44092 /Cr-1667; with same data.

Type locality. The south-west shelf of Sakhalin Island, Tatar Strait , Sea of Japane, Far East of Russia (47°45'N 142°00'54"E) .

Description. Male (12 mm). Vital body color is dark grey with light rims behind of the each body segment. Thoracic segments smooth dorsally ( Fig. 8 a, c, 28b). Pleon segments 1–2 with central tooth and 1–2 lateral denticles on each side; pleon segment 3 with posterior row of 6 subequal teeth. Urosome segment 1 with central tooth and with 2 lateral teeth on each side (1 large tooth and 1 small denticle); urosome 2 with 2 lateral pairs of teeth and with the simple cuspidate seta in the each pair.

Head: ( Fig. 8 b) 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. 9 a) nearly 75% of body length, slender; flagellum exceeding 1.7 times the length of the peduncle, bearing 29+ articles, few very thin and short setae scattered along flagellum; peduncle article 1 double width but 0.85 times as long as article 2, with 5 stout simple setae along posterior margin, article 3 0.38 times as long as article 2; accessory flagellum 4–5-articulate.

Antenna 2: ( Fig. 9 b) flagellum almost 0.54 times as long as peduncle, 13 articles, with few thin setae on each article; peduncle articles 5 slightly shorter than article 4, articles 1, 2, 3 together 1.5 times shorter than article 4 or article 5 each; article 2 with protruding lobe reaching the 3/4 of the article 3 length; articles 4 and 5 with numerous evenly spaced tufts of thin setae.

Mouthparts. Labrum: ( Fig. 9 c) frontal margin slightly concave medially, densely covered by minute setae.

Mandible: ( Fig. 9 d, e) incisor crenulate and stretching in a rounded tip; raker setae stout serrated, numerous (13–14), subequal to incisor in length; molar flattened triturative; palp 3-articulate, palp segment 2 sparsely setose, palp segment 3 distally sparsely setose, 1-st article with protruding lobe, the percentage of total length of the articles of the palp 19% (article 1), 33% (article 2) and 48% (article 3).

Labium: ( Fig. 9 f) inner lobes small but well defined, rounded; outer lobes rounded, with minute setae at tips.

Maxilla 1: ( Fig. 9 g) inner plate rounded-triangulate, lined with a row of plumose setae (16–17 setae); outer plate elongate , 1.5 times as long as inner plate, apically with 2 rows of 9 bifurcate and comblike strong setae; palp 2-articulate, article 2 1.8 times as long as article 1, article 2 apical margin with two rows of 9–10 simple setae each.

Maxilla 2: ( Fig. 9 h) inner plate slightly shorter than outer plate, facial setae of inner plate numerous, located submarginal-dorsally, tip covered with numerous simple setae; outer plate with numerous simple setae on the tip, subapically with a rare row of 9–10 setae.

Maxilliped: ( Fig. 10 a) inner plates medium size, fully cleft, distal margin with a row of 3 teeth, inner margin with long plumose setae (8–10 setae); outer plates reaching ½ length 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 several transverse bundles of short setae submarginally; palp 4-articulate, the percentage of total length of the articles of the palp are 11% (article 1), 39% (article 2), 25% (article 3), 25 (article 4), article 2 with numerouse setae along inner margine; tip of article 3 bilobed with a crown of long simple setae; article 4 inner margin with a line of simple setae.

Pereopod 1 (gnathopod 1): ( Fig. 10 b, c) coxa extended distally, with rounded anterior corner; basis straight with a row of simple setae at the distal part of anterior margin and with rare long setae along posterior margin; ischium with 2 tufts of long setae along posterior margin and with a dense bundle of setae at the postero-distal corner; merus subrectangular, with a row of simple setae along distal margin and with a dense row of short setae at the posterior margin; carpus long, slightly longer than propodus, 6 oblique rows of long serrate setae along outer posterior margin, with a row of long setae along anterior part of distal margin and tomentose at the anterior-distal corner; propodus suboval, with 5 groups of long serrate setae along posterior margin, with 5 tufts of long simple setae along anterior margin and with a dense bunch of long simple setae at the anterior distal corner, palm rounded, smoothly 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, inner surface with the single long seta distally; dactylus as long as palm, strongly curved near the base, with nail and with tooth-like protrusion as long as nail above it.

Pereopod 2 (gnathopod 2): ( Fig. 10 d, e, 11a) coxa rounded, slightly narrowing distally, gills with indistinct peduncle; basis slightly expands medially and distally, 1.2 times as long as coxa, with a few long simple setae along posterior margin and with a row of short setae along anterior margin; merus subrectangular with small acute protrusion at the posterior distal corner, with 2 rare groups of setae along posterior margin; carpus triangular, 2.3 times shorter than propodus; propodus suboval, palm oblique, rounded, with slight protuberances, palmar corner with small denticle, with small strong simple setae along the palmar margin, anterior margin lined with 4 groups of setae, posterior margin with numerous tufts of serrate setae; dactylus inflated, slightly shorter than palm, slightly curved to the inside of propodus, inner margin with a rare row of short simple setae, outer margin with a rare short setae, tip of dactylus obtuse.

Pereopod 3: ( Fig. 11 b) coxa slightly longer than coxa 2, rounded distally; basis linear with few minute setae along anterior margin and with rare long simple setae along posterior margin; merus long with 2 strong simple setae along anterior margin and with a single cluster from one strong simple seta and few small setae at the anterior distal corner, posterior margin with 2 tufts of thin setae, posterior distal corner with a bunch of thin setae; carpus as long as merus, with 5 groups of strong simple setae along posterior margin; propodus linear, more narrow and as long as carpus, with 4 groups of short strong simple setae along posterior margin; dactylus small (0.3 times length of propodus), with nail.

Pereopod 4: ( Fig. 11 c) coxa subequal in length to coxa 3, anterior and posterior corners rounded, posteriorly excavated; segements 3–7 shorter than in pereopod 3. Armaments of articles of pereopod 4 similar to pereopod 3.

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

Pereopod 5: ( Fig. 11 d) coxa with slightly rounded front margin, with quadrate hind margin and with rounded anterior lobe pulled down; basis regular, with posterior wing, width 0.67 times as long, posterior distal corner rounded, hind margin crenulated, anterior margin with small stout setae; ischium subquadratic; merus slightly broaded medially, with 4 short stout setae along anterior margin, with 2 short stout setae at the middle of posterior margin, with 2 strong stout setae at the posterior distal corner; carpus 0.86 times as long as merus, with 2 groups of 2 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 2–3 bunches of strong simple setae along anterior margin; dactylus small (0.26 times length of propodus), with nail.

Pereopod 6: ( Fig. 11 e) coxa with quadrate hind margin and with anterior lobe pulled back and down, front margin with few short simple setae; basis regular, with posterior wing, width 0.55 times as long, posterior distal corner slightly rounded, hind margin crenulated, anterior margin with small stout setae; ischium subquadratic; merus long, with 3 short stout simple setae along anterior and posterior margins each, and with clusters of 2–3 strong stout setae at anterior and posterior distal corners each; carpus 0.9 times as long as merus, with 2 groups 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 and posterior margins each; dactylus small (0.25 times length of propodus), with nail.

Pereopod 7: ( Fig. 11 f) coxa small, without distinct anterior lobe and with rounded posterior lobe; basis regular, with posterior wing, broaded medially, width 0.66 times of length, posterior distal corner rounded, posterior margin crenulated, anterior margin with small cuspidate setae; ischium subquadratic; merus long, with 2 groups of short cuspidate setae along anterior and posterior margins each, and with single cluster of 3–4 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 slightly smaller than gill 5.

Epimeral plates: ( Fig. 12 a, b, c) plate 1 with oblique crest, posterior margin rounded, with 1–2 notches, lower margin with 1–2 strong simple setae, hind corner with a small tooth; plate 2 posterior margin straight, ventral margins convex, with oblique crest, posterior margin with 5–6 indistinct notches, ventral margin with a row 5–6 strong simple setae; plate 3 hind corner produced, acute, posterior margin concave, ventral margin with a row of 11–12 strong simple setae.

Pleopods: ( Fig. 12 d–g) normal, no sexual dimorphism; peduncle with two specific toothed coupling setae and one cuspidate seta on the inner corner; coupling basis of inner ramus with 5–4 of specific stout two-pointed cuspidate setae along inner margin: pleopod 1 (5), pleopod 2 (5), pleopod 3 (4).

Uropod 1: ( Fig. 12 h) peduncle with strong interramal spur; rami subequal in length, 0.89–0.95 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. 12 i) peduncle shorter than outer ramus (0.82 ramus length); inner ramus shorter than outer, with numerous simple cuspidate setae along outer margin; uropod 2 shorter than uropod 1.

Uropod 3: ( Fig. 12 j) long, 1.3 times as long as uropod 1; peduncle shorter than peduncle of uropod 1, with one cuspidate seta at the anterior margin, with two clusters of simple cuspidate setae at the apex; elongate 2-articulate outer ramus (8 times length of inner ramus) 2.7 times as long as peduncle, with 5 tufts of small simple stout setae along anterior and posterior margins of article 1 each, article 2 minute, more than 13 times shorter than article 1; inner ramous short and ovoid with two cuspidate setae at the tip.

Telson: ( Fig. 12 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.

Female (10.6 mm). Vital body color is dark grey with light rims behind of the each body segment. Dorsal carination as in male ( Fig. 13 a, b).

Antenna 1: ( Fig. 13 c) similar to as in male, 62% of body length, slender; flagellum exceeding 1.4 times the length of the peduncle, 30 articles; peduncle article 1 1.3 as long as article 2; article 3 0.36 times as long as article 2; accessory flagellum 4-articulate + one reduced.

Antenna 2: ( Fig. 13 d) flagellum almost 0.5 times as long as peduncle, 9 articles; peduncle articles 4 slightly shorter than article 5, articles 1, 2, 3 together 1.4 times shorter than article 4 or article 5 each; article 2 with protruding lobe reaching the 3/4 of the article 3 length; articles 4 and 5 with numerous evenly spaced tufts of thin setae.

Mouthparts as in male.

Maxilla 1: ( Fig. 13 e) inner plate with a row of plumose setae (12 setae).

Pereopod 1 (gnathopod 1): ( Fig. 14 a, b) coxa slightly extended distally, with rounded anterior corner; basis straight with a row of long simple setae at the distall part of anterior margin and with rare long setae along proximal part of posterior margin; carpus long, 1.25 times as long as propodus, 5 oblique rows of long serrate setae along outer posterior margin, with a row of long setae along anterior part of distal margin, with two speciphic plumose setae at the anterior distal and posterior distal corners each; propodus with 5 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 slightly oblique, formed with posterior margin the obtuse angle, minutely serrate with a row of numerous short stout simple setae, inner surface with a transverse row of long setae submarginally; dactylus as long as palm, with nail and with tooth-like protrusion as long as nail above it.

Pereopod 2 (gnathopod 2): ( Fig. 14 c) coxa long, rounded distally; basis straight, subequal to coxa, with a few long simple setae along posterior margin and with a row of short setae along anterior margin; merus subrectangular, with acute protrusion at the posterior distal corner, with a rare long setae along distal margin; carpus slightly broadened distally, 1.2 times shorter than propodus, posterior margin with 5 clusters of setae; propodus width 0.62 times as length, palm slightly oblique, with stout cuspidate setae near the posterior distal corner, anterior margin with 5 tufts of long simple setae, posterior margin with 6 tufts of setae; dactylus as long as palm, slightly curved to the inside of propodus, outer margin rarely setose, tip of dactylus acute.

Pereopods 3 and 4 as in male ( Fig. 14 d, e): merus of pereopod 3 with 2 long cuspidate setae along anterior margin.

Pereopods 5–7 ( Fig. 15 a–e) elongated from pereopod 5 to pereopod 6, pereopods 6 and 7 equal in length. Coxa 5 and 7 as in male ( Fig. 15 a, b, e). Coxa 6 with sexual dimorphism ( Fig. 15 c, d): anterior lobe longer than in male.

Pereopod 5 ( Fig. 15 a, b): merus with 2 short stout setae along anterior margin.

Pereopod 6 ( Fig. 15 c, d): merus and propodus with 2 tufts of long cuspidate setae along anterior margin each.

Pereopod 7 ( Fig. 15 e): merus and propodus with 2 tufts of long cuspidate setae along anterior margin each.

Oostegites long oval, with numerous long setae.

Epimeral plates and pleopods as in male.

Uropod 1 ( Fig. 15 f) similar to same in male.

Uropod 2: ( Fig. 15 g) ramous with 3–4 simple cuspidate setae along outer margin (in male 5–6).

Uropod 3: ( Fig. 15 h) elongate 2-articulate outer ramus with 4 tufts of small simple stout setae along anterior and posterior margins of article 1 each (in male 5).

Sexual dimorphism: In structure of pereopod 2, in form of coxa 6 and in the armament of uropod 3. Pereopod 2 in male bigger than in female; carpus in male more shorter than in female; propodus big, with small tooth at the posterior distal angle; dactylus heavy, inflated, with obtuse tip. Outer ramus of uropod 3 in male bears 5 tufts of small simple stout setae along anterior and posterior margins of article 1 each (in female only 4 tufts).

Variations: In exemplars from south-eastern Sakhalin shelf the central denticle at the posterior margin of pleon segment 1 is smaller than in exemplars from Tatar Strait; dorsolateral groups of teeth of urosomal segment 1 only with single tooth each ( Fig. 28 c).

Etymology. Named in a memory of Russian carcinologist Andrey K. Klitin.

Ecology. A. klitinii was found at the depth of 20 m on sand and gravel bottoms in the south western shelf of Sakhalin and in channel of marine lagoon lake Ptichje (south eastern Sakhalin). Females with oostegites and eggs in marsupium were detected in all localities in May.

Distribution. Tatar Strait of Japan Sea near the south west coast of Sakhalin island; Okhotsk Sea, south east coast of Sakhalin Island ( Fig. 2 ).

Remarks. According to the formula of dorsal carination Abludomelita klitinii sp. nov. is closely resembles to A. denticulata ( Nagata, 1965) , A. breviarticulata ( Ren, 2012) , A. huanghaiensis ( Ren, 2012) and A. okhotensis sp. nov. A. klitinii differs from A. denticulata by the dorsal carination of pleon segment 3: A. klitinii have 6–7 subequal teeth along posterior margin; A. denticulata bear 5 teeth, the central of these is largest. Accessory flagellum of antenna 1 of A. klitinii is 4–5-articulate; in A. denticulate accessory flagellum is 1-articulate.

A. klitinii differs from A. breviarticulata by the structure of pereopod 2 of male and female: in A. klitinii carpus of pereopod 2 in male with broad posterior lobe, palm oblique, rounded, with slight protuberances, palmar corner with small denticle; propodus of female is not inflated, palm slightly oblique, without teeth. In A. breviarticulata carpus of pereopod 2 in male with narrow posterior lobe, palm oblique, with few protuberances, palmar corner with large acute tooth; propodus of female is inflated, palm oblique, with numerous teeth.

A. klitinii differs from A. huanghaiensis by the structure of pereopod 1 of male and pereopod 2 of female, by the shape of epimeral plate 3 and by the shape of basis of pereopod 7: in A. klitinii propodus of pereopod 1 in male suboval, dactylus as long as palm, strongly curved near the base; propodus of pereopod 2 of female short, palm slightly oblique; posterior margin of epimeral plate 3 without distinct serration; posterior margin of basis of peropod 7 is rounded. In A. huanghaiensis palmar margin of pereopod 1 (gnathopod 1) of male very oblique, concave, longer than the posterior margin of propodus; palmar margin of pereopod 2 (gnathopod 2) of female very oblique, as long as the posterior margin; posterior margin of epimeral plate 3 with numerous teeth; posterior margin of basis of peropod 7 straight.

A. klitinii differs from A. okhotensis by the dorsal carination of pleon segments 1 and 2: in A. klitinii the dorsal row of teeth include 5 teeth, the central is largest; in A. okhotensis the dorsal row consist of 6–7 teeth, the central tooth is small.

Figures

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

FIGURE 8. Abludomelita klitinii sp. n., holotype, male: a—lateral view, b—cephalon, c—dorsal carination; scale: a, b— 1 mm; c— 2 mm.

FIGURE 9. Abludomelita klitinii sp. n., holotype, male: a—antenna 1, b—antenna 2, c—upper lip, d—right mandible, e—left mandible, f—low lips, g—maxilla 1, h—maxilla 2; scale: a, b— 1 mm; c, d, e, f, g, h— 0.1 mm.

FIGURE 10. Abludomelita klitinii sp. n., holotype, male: a—maxilliped, b—pereopod 1, c—inner side of propodus and dactylus of pereopod 1, d—pereopod 2, e—inner side of propodus and dactylus of pereopod 2; scale— 1 mm.

FIGURE 11. Abludomelita klitinii sp. n., holotype, male: a—inner side of propodus and dactylus of pereopod 2, b—pereopod 3, c—pereopod 4, d—pereopod 5, e—pereopod 6, f—pereopod 7; scale: b – f— 1 mm.

FIGURE 12. Abludomelita klitinii sp. n., holotype, male: a—epimer 1, b—epimer 2, c—epimer 3, d—pleopod 3, e—coupling spines of pleopod 3, f—coupling setae of pleopod 2, g—coupling setae of pleopod 3, h—uropod 1, i—uropod 2, j—uropod 3, k—telson; scale: a, b, c, d, h, i, j, k— 1 mm; e, f, g— 0.1 mm.

FIGURE 13. Abludomelita klitinii sp. n., paratype, female: a—lateral view, b – dorsal carination, с—antenna 1; d—antenna 2, e—maxilla 1; scale: a, c, d— 1 mm; b— 0.5 mm; e— 0.1 mm.

FIGURE 14. Abludomelita klitinii sp. n., paratype, female: a – pereopod 1, b—inner side of propodus and dactylus of pereopod 1, c—pereopod 2, d—pereopod 3, e—pereopod 4; scale: a, c – e— 1 mm; b— 0.1 mm.

FIGURE 15. Abludomelita klitinii sp. n., paratype, female: a—coxa 5, b—pereopod 5, c—coxa 6, d—pereopod 6, epereopod 7, f—uropod 1, g—uropod 2, h—uropod 3, i - telson; scale: a – h— 1 mm; i— 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.