Cognateosymtes serraticoxae Labay 2018, sp. nov.
Creators: name: Labay, Vjacheslav S.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Pleustidae
Cognateosymtes
Cognateosymtes serraticoxae

description: Cognateosymtes serraticoxae sp. nov.
Figures 1–8
Diagnosis. With the characters of the genus. Eyes large, subreniform. Body medium, smooth; urosome segment 2 not occluded dorsally.
Rostrum short, about 1/6 times as long as peduncular segment 1 of antenna 1, apex acute. Antenna 1, segment 2 of peduncle with small anterodistal process, accessory flagellum minute, scale-like; flagellum with 34 articles, length about 3.5 x peduncle. Lower lip, outer lobes rounded not widely spread. Mandible, incisor margins with 6–7 teeth, accessory spine rows with 6 slender blades; molar with strongly ridged grinding surface and with a medial molar seta; palp segment 3 slightly shorter than segment 2, segment 2, inner margin setose; segment 1 without setae. Maxilla 1, inner plate with 2 plumose apical setae; outer plate with 9 strong pectinate setae (spine-like setae). Maxilliped, inner plate reaching the middle of palp segment 1; outer plate reaching about 0.5 x length of palp segment 2; palp segment 2 the longest; segment 3 narrower, slightly broadened medially; dactylus slender, slightly curved and shorter than palp segment 3. Coxal plate 1–3 medium; coxa plate 4 much broader, deeply excavated posteroproximally; coxal plates 5–7 posterolobate, posteriorly rounded. Pereopod 1, merus with acute tooth posterodistally, palmar margin without medial tooth, with 2 clusters of posterodistal strong setae (spines). Pereopod 2 slightly widened; carpal lobe short, merus without acute tooth posterodistally. Pereopods 5–7, dactylus medium in length, 0.44–0.5 times as long as propodus. Epimeral plate 3, posteroventral corner without a large process.
Male: unknown.
Type material. Holotype female, 6 mm, Х 50437 /Cr-2276, Tatar Strait. Sea of Japan, Far East of Russia (49°29.5'N 142°06.3'E, 17 m), rocks, M.G. Rogotnev, 13 July 2017. Paratypes: 1 female, 6 mm, Х 50438 /Cr-2277, with same data as holotype; 1 female, 6 mm, Х 50439 /Cr-2278, with same data as holotype.
Type locality. The western coast of Sakhalin Island, Tatar Strait. Sea of Japan, Far East of Russia (49°29.5'N 142°06.3'E, 17 m).
Description. Female (6 mm). Vital body color is unknown; color in alcohol almost colourless, uniformly pale yellow. Body medium, smooth (Fig. 2a).
Head (Fig. 2b): slightly shorter than pereonites 1 & 2 combined, rostrum about 1/5 times as long as peduncular segment 1 of antenna 1; eyes large, subreniform; anterior head lobe prominent, truncated, lower margin processed ahead by the acute tooth. Antenna 1 (Fig. 2c): medium length, nearly 40% of body length; flagellum bearing 34 articles; peduncle article 1 is 2 times as long as the length of article 2, with a few simple setae at the distal corner of posterior margin, segments 1 & 2 with large anterodistal process each, article 3 0.38 times the length of article 2; accessory flagellum, scale-like. Antenna 2 (Fig. 2d): destructed, articles 1, 2 together slightly shorte than article 3; article 1 with long anterodistal protrusion. Labrum (Fig. 2e): apical lobes slightly asymmetric, setose. Mandible (Figs. 2f, 3a, b, c): molar strong, columnar, with pavement-type grinding surface and with a medial molar plumose seta; palp 3-articulate, article 1 of palp without setae, palp segment 2 with a row of 12 simple setae (D-2 setae), palp segment 3 with posterior row of 15–16 specific plumose D3-setae (proximal setae are needle-like with forked tip, middle setae are plumose with forked tip and distal setae are comb-like), with group of 3 long simple distal E3- setae and one short simple E-3 seta. Labium (Fig. 3d): inner lobes small; outer lobes rounded, setose. Maxilla 1 (Fig. 3e): inner plate long, slightly narrowed distally, with 2 plumose setae apically; outer plate elongate, apically with 2 rows of 9 strong setae (external setae bifurcate, middle and internal setae pectinate); palp 2-articulate, article 2 with a distal row of thin simple setae at the outer margin and with a subapical row of 9 simple setae, apical margin of article 2 of left maxilla 1 with 8 long stout spine-like setae, apical margin of article 2 of right maxilla 1 with 8 short teeth-like setae. Maxilla 2 (Fig. 4a): inner plate with 2 strong plumose setae on the inner margin. Maxilliped (Fig. 4b): inner plates middle length, fully cleft, with 3 short conate setae (Watling type II.A4) (Watling 1989) at the truncated apex; outer plate elongated, rounded apically, inner margin with submarginal row of simple setae, apex with one strong seta only; palp 4-articulate, the percentage of total length of the articles of the palp 25% (article 1), 31% (article 2), 24% (article 3) and 20% (article 4); article 4 (dactylus) slender, slightly curved.
Pereon: Pereopod 1 (gnathopod 1) (Fig. 4c, d): coxa short, slightly pulled forward and down, with 4 small posterodistal cusps; basis slightly convex posteriorly, with dense anterior submarginal row of simple setae at the inner surface; merus with a tuft of 2 simple setae at the border of 1/2 of posterior margin, distal margin with a row of long simple setae; carpus 0.86 times as long as propodus, posterior lobe shallow, with a tuft of 2 simple setae at the border of 1/6 of posterior margin, with posterodistal row of numerous simple setae passing to the distal margin; propodus suboval, 2 times as long as wide, palmar margin smoothly oblique, roundly passing to the posterior margin, 0.64 times as long as posterior margin, without medial tooth, with 3 clusters of posterodistal robust setae; dactylus as long as palmar margin of propodus, curved. Pereopod 2 (gnathopod 2) (Fig. 4e, f): coxa deep, with 3 posterodistal cusps; basis linear, with a row of rare short simple setae anteriorly; merus with a few simple setae at the border of 1/2 of posterior margin, distal margin truncated, with a few simple setae and with a acute tooth at the posterior angle; carpus medium, 0.83 times as long as propodus, posterior lobe shallow, with 4 tufts of setae along posterior margin; propodus suboval, 1.93 as long as wide, with 4 groups of simple setae at the posterior margin, palmar margin smoothly oblique, 0.8 times as long as posterior margin, without medial tooth, with 2 clusters of posterodistal strong setae (spines); dactylus slightly shorter than palmar margin. Pereopod 3 (Fig. 5a): coxa deep, 1.7 times as long as wide, rounded anterodistally, with posterior tooth and with 2 small posterodistal cusps; leg slender; basis linear; merus as long as carpus, produced slightly forwards along anterior margin of carpus; propodus long, 1.28 times as long as carpus; dactylus short, 0.5 times as long as propodus. Pereopod 4 (Fig. 5b): coxa 1.26 times as long as wide, narrowed and rounded distally, with deep excavation posteromarginally; basis to dactylus as for pereopod 3. Pereopod 5 (Fig. 5c): coxa antero- and posterolobate, with rounded ventral front margin, posterior lobe rounded; basis with posterior lobe, width 0.69 times as length, posterior margin slightly convex, crenulated; merus slightly produced forwards along posterior margin of carpus; carpus more narrow and 0.8 times as long as merus; propodus linear, 1.4 times as long as carpus; dactylus short, 0.44 times as long as propodus, weakly curved, slender. Pereopod 6 (Figs. 5d): coxa posterolobate, with rounded front margin, posterior lobe subovate, pulled back and down; basis suboval, broadened, with distinct posterior lobe, posterodistal corner rounded, width 0.73–0.75 times as length, posterior margin convex, crenulated; merus produced distally along posterior margin of carpus, narrow; carpus 0.8 times as long as merus; propodus linear, 1.5 times as long as carpus; dactylus short, 0.5 times as long as propodus, weakly curved, slender. Pereopod 7 (Fig. 6a): coxa posterolobate, anterior margin rounded, posterior lobe subquadrate, rounded posteroventrally; basis broadened, with distinct posterior lobe, posterodistal corner rounded, width 0.77–0.78 times as length, posterior margin convex, crenulated; ischium; merus, carpus, propodus and dactylus as in pereopod 6. Coxal gills 2–6. Coxal gill 6 is smaller than gill 5.
Pleon: Epimeral plates: (Fig. 6b, c, d) plates 1–3, posterior corners with small tooth each; plate 1 rounded triangular, with 2–3 short spine-like setae along ventral margin; plate 2, ventral margin slightly convex, with 3 spine-like setae; plate 3, posterior margin rounded, ventral margin straight with 3 spine-like setae. Pleopods: (Fig. 6e, f, g, h, i) normal; inner ramus slightly shorter than outer ramus, coupling basis of inner ramus with 3–5 specific stout two-pointed plumose setae along inner margin (5 setae on pleopod 1, 4 setae on pleopod 2 and 3 setae on pleopod 3). Uropod 1: (Fig. 7a) peduncle 1.2 times as long as outer ramus; outer ramus 0.89 times as long as inner ramus. Uropod 2: (Fig. 7b) inner ramus 1.4 times longer than peduncle, outer ramus 0.66 times as long as inner. Uropod 3: (Fig. 7c) inner ramus 2.6 times longer than peduncle, with acute and non-spinose apex; outer ramus about 0.59 times as long as inner; outer ramus with a row of 4–6 small spine-shaped setae along lateral and medial margins each, with acute and non-spinose apex. Telson: (Fig. 7d) medium in length, linguiform, apically rounded, length about 1.4 x width, with proximal ventral keel, plumose marginal penicillate setae are absent.
Male: unknown.
Variations: Coxa 1 with 4–5 small posterodistal cusps (Fig. 8a), coxa 2 with 3–4 small posterodistal cusps.
Etymology. Species name serraticoxae based on a Latin words “ serratis ” (serrated) and “coxa”, that is caused by shape of coxal plates: with a ventral margin serrated posteriorly. The name is masculine in gender.
Ecology. C. serraticoxae was found in the depth 17 m on rock bottoms. Females with developed oostegites were detected in the type locality in July.
Distribution. The northern part of the Sea of Japan, Tatar Strait, the shelf of south-western Sakhalin Island (Fig. 1).
description: Published as part of Labay, Vjacheslav S., 2018, Cognateosymtes serraticoxae, new genus, new species, a pleustid amphipod from the Sea of Japan (Crustacea: Amphipoda: Gammaridea: Pleustidae: Eosymtinae), pp. 220-230 in Zootaxa 4521 (2) on pages 223-228, DOI: 10.11646/zootaxa.4521.2.4, http://zenodo.org/record/2609817