Hendrycksopleustes neimanii, Labay, 2021

Labay, Vjacheslav S., 2021, Review of amphipods of the family Pleustidae Buchholz, 1874 (Crustacea Amphipoda) from the coastal waters of Sakhalin Island (Far East of Russia). I. Subfamily Neopleustinae Bousfield & Hendrycks, 1994, Zootaxa 4974 (2), pp. 267-306 : 277-285

Hendrycksopleustes neimanii sp. nov.

Figures 1l , 2h, n, w , ae, 3h, 4l, 5k, 6–11, 22

Diagnosis. With the characters of the genus. Body segments strongly carinated dorsally from pereon segment 6 to pleon segment 2, pleon segment 3 with sloping low ridge dorsally.

Rostrum short, about 0.1 times as long as peduncular segment 1 of antenna 1, apex acute. Antenna 1, segment 2 of peduncle with small rounded anterodistal process, accessory flagellum minute, scale-like; flagellum with 71 articles, length about 4.6x peduncle. Lower lip, outer lobes rounded, widely spread. Mandible, molar weak and without a medial molar seta; palp segment 3 subequal to segment 2, segment 2, inner margin setose; segment 1 without setae. Maxilla 1, inner plate with 2 plumose apical setae, rarely with single seta; outer plate with 9 strong pectinate setae (spine-like setae). Maxilliped, inner plate reaching the middle of outer plate basis; outer plate reaching about 0.2x length of palp segment 2; palp segment 1 subequal in legth to segments 2 and 3 each; dactylus slender, slightly curved and slightly shorter than palp segment 3. Coxal plate 1–3 medium; coxal plate 4 much broader, deeply excavated posteroproximally; coxal plates 5–6 posterolobate, posteriorly rounded, coxal plate 7 trapezoidal, with rectangular posterodistal angle. Pereopod 1, merus with posterodistal tooth, palmar margin with medial tooth, with a row of 5 strong spineformes setae along posterior part and with 5 transversal clusters of posterodistal strong setae (spines). Pereopod 2, carpal lobe long, merus with posterodistal tooth, palmar margin with medial tooth and with a row of 6–7 strong spineformes setae along posterior part and with 5 transversal clusters of posterodistal strong setae (spines). Pereopods 5–7, dactylus medium in length, 0.46–0.49 times as long as propodus. Epimeral plates 1–3, posteroventral corner with acute process.

Male similar to female.

Type material. Holotype female, 12 mm, Х 53857 /Cr-2402, Sea of Okhotsk , Far East of Russia (53°45′37.010 N 143°37′57.186 E, 104 m), pebbles with sands and silt, M.G. Rogotnev, 29 August 2018 . Paratypes: 1 male, 8.8 mm, Х 53858 /Cr-2403, with same data as holotype ; 1 female, 13.3 mm, Х 53859 /Cr-2404, with same data as holotype; 3 females, Х 53860 /Cr-2405, with same data as holotype .

Type locality. The eastern coast of Sakhalin Island , Sea of Okhotsk, Far East of Russia (53°45′37.010 N 143°37′57.186 E, 104 m) .

Description. Female (12 mm). Vital body color unknown; color in alcohol almost colourless, uniformly pale yellow. Body medium, with the carination characters of the genus.

Head: shorter than pereonites 1 and 2 combined, without anterodorsal crest, rostrum about 0.1 times as long as peduncular segment 1 of antenna 1; eyes medium, ellipsoid, pigmented; anterior head lobe prominent, truncated, lower margin rounded. Antenna 1: long, nearly 80% of body length; flagellum bearing 71 articles; peduncle article 1 is 1.25 times as long as the length of article 2, with a few simple setae at the distal corner of posterior margin, without anterodistal process, article 3 is 1/3 times the length of article 2; accessory flagellum reduced. Antenna 2: flagellum with 33 articles; peduncle articles 5 slightly shorter than article 4, articles 1–3 combined subequal to article 4; article 2 with long posterodistal protrusion, subequal to article 3 length. Labrum: apically bilobate and asymmetrical, without setae. Mandible: molar small, conical, with small conical wart at the axis, and with microsetae, without triturating surface and without a medial molar plumose seta; palp 3-articulate, article 1 of palp without setae, palp segment 2 with a row of 13–16 simple setae (D-2 setae), palp segment 3 with posterior row of 12 specific plumose D3-setae, with group of 4 medium length simple distal E3-setae. Labium: inner and outer lobes pubescent. Maxilla 1: inner plate short, rounded distally, with 2 (less often one) plumose setae apically; outer plate subquadrate, apically with 2 rows of 9 strong comb setae; palp 2-articulate, article 2 with a distal row of thin simple setae at the outer margin and with a subapical row of 5–6 simple setae, apical margin of article 2 of with 5–7 stout spine-like setae. Maxilla 2: inner plate with one strong plumose seta on the inner margin. Maxilliped: inner plates short, fully cleft, with 5 button spineformes setae (Watling type II.A3) ( Watling 1989) at the truncated apex; outer plate short, subrounded apically, inner margin with submarginal row of simple setae, apex with 3 strong cuspidate setae; palp 4-articulate, the percentage of total length of the articles of the palp 21–23% (article 1), 25–26% (article 2), 29% (article 3) and 23–25% (article 4); article 4 (dactylus) slender, slightly curved.

Pereon: Pereopod 1 (gnathopod 1): coxa medium depth, with central ventral rounded angle, with 3 small posterodistal cusps; basis linear, with dense row of simple setae along anterior margin and with rare simple setae along posterior margin; merus with a tuft of 2 simple setae at the border of 1/2 of posterior margin, distal margin with a dense row of long simple setae; carpus 0.4 times as long as propodus, posterior lobe medium, with a dense row of simple setae along posterior margin; propodus almond-shaped, 2.3 times as long as wide, palmar margin subvertical, with medial tooth at the border of anterior 1/6 of palmar margin length, posterior margin indistinct; dactylus curved, 5/6 times as long as palmar margin of propodus. Pereopod 2 (gnathopod 2): coxa deep, rounded down, with 2 posterodistal cusps; basis linear, with a row of rare short simple setae anteriorly and with 3 tufts of simple setae in the distal half of posterior margin; merus with an acute tooth at the posterior angle, with a few simple setae at the border of 1/2 of posterior margin and with a tuft of simple setae near the base of posterodistal tooth, distal margin truncated; carpus short, 0.4 times as long as propodus, posterior lobe narrow and long, with a dense row of simple setae along posterior margin and with a row of strong cuspidate setae at the posterior part of distal margin; propodus almond-shaped, 2 times as long as wide, palmar margin subvertical, with medial tooth at the border of anterior 1/6 of palmar margin length, posterior margin indistinct; dactylus curved, 0.9 times as long as palmar margin of propodus. Pereopod 3: coxa deep, 1.9 times as long as wide, rounded distally, with 1–2 posterior teeth; leg slender; basis linear, with rare short setae along anterior and posterior margins; merus 1.5 times as long as carpus, produced slightly forwards along anterior margin of carpus, with 3–5 groups of few simple setae along anterior margin and with 5 clusters of few simple setae along posterior margin; propodus long, 1.36 times as long as carpus, with 7–8 groups of short strong cuspidate setae along posterior margin; dactylus short, 0.46 times as long as propodus. Pereopod 4: coxa 1.14 times as long as wide, narrowed and rounded distally, with deep excavation posteromarginally; basis to dactylus as for pereopod 3. Pereopod 5: coxa antero- and posterolobate, with rounded ventral front margin, posterior lobe rounded; basis with posterior wing, width 0.68 times length, anterior margin with 7–8 groups of 1–2 short strong cuspidate setae, posterior margin convex, crenulated; merus slightly produced forwards along posterior margin of carpus, with 5–6 cuspidate simple setae along anterior and posterior margins each; the leg from carpus to dactylus missing. Pereopod 6: coxa posterolobate, with oblique front margin, posterior lobe subovate, pulled back and down; basis with posterior wing, width 0.71–074 times as length, anterior margin with 7–8 groups of 1–2 short strong cuspidate setae, posterior margin convex, crenulated; merus slightly produced forwards along posterior margin of carpus, with 5–6 cuspidate simple setae along anterior and posterior margins each; carpus 0.69 times as long as merus, with 4 clusters of strong cuspidate setae along anterior margin; propodus linear, 1.22 times as long as carpus; dactylus short, 0.46 times as long as propodus, weakly curved. Pereopod 7: coxa trapezoidal; basis with posterior wing, width 0.7 times as length, anterior margin with 6–7 groups of 1–2 short strong cuspidate setae, posterior margin convex, crenulated; merus slightly produced forwards along posterior margin of carpus, with 5–6 cuspidate simple setae along anterior and posterior margins each; the leg from carpus to dactylus missing. Coxal gills 2–6, ovate. Coxal gill 6 smaller than gill 5.

Pleon: Epimeral plates: plate 1 rounded triangular, posterior corner with small acute tooth, posterior margin convex, lower margin with 3 strong cuspidate setae along anterior half; plate 2 with acute posteroventral process, ventral margin with 5 spine-like cuspidate setae in anterior 2/3, posterior margin convex; plate 3 with long acute posteroventral process, posterior margin convex, ventral margin straight with 5 spine-like setae. Pleopods: normal; inner ramus slightly shorter than outer ramus, coupling basis of inner ramus with 5–6 specific stout two-pointed plumose setae along inner margin (6 setae on pleopod 1, 5 setae on pleopods 2 and 3). Uropod 1: peduncle 1.22 times as long as outer ramus; outer ramus the shorter, 0.91 times as long as inner ramus. Uropod 2: inner ramus 1.8 times as long as peduncle, outer ramus the shorter, 0.66 times as long as inner. Uropod 3: inner ramus 3 times as long as peduncle, with acute and non-spinose apex; outer ramus about 0.6 times as long as inner; outer ramus with a row of 5–6 small spine-shaped setae along lateral and medial margins each, with acute and non-spinose apex. Telson: ( Fig. 6i ) linguiform, apically rounded, length about 1.58x width, with proximal ventral keel, plumose marginal penicillate setae are absent.

Male similar to female.

Etymology. Named in honor of famous Russian oceanographer Victor G. Neiman. The name is masculine in gender.

Ecology. H. neimanii was found at the depth of 104 m on pebbles sediments with sands and silt. Females with eggs in marsupium were detected in the type locality in August.

Distribution. The north-east shelf of Sakhalin Island, Sea of Okhotsk ( Fig. 22 ).

Figures

FIGURE 1. Neopleustinae Bousfield & Hendrycks, 1994, lateral view: a—Neopleustes boecki boecki (Hansen, 1888) (from Sars 1895: pl. 122), b—N. boecki pacifica ssp. nov., c—N. carinatus Margulis, 1963 (original image by author), d—N. columbianus Hendrycks & Bousfield, 2004 (from Hendrycks & Bousfield 2004: fig. 27), e—N. euacanthoides Gurjanova, 1972 (modified from Gurjanova 1972: fig. 18), f—N. euacanthus (G. Sars, 1876) (modified from Sars 1885: Pl. 14), g—N. kussakini (Budnikova, 1995) (modified from Budnikova 1995), h—N. pulchellus pulchellus (Krøyer, 1846) (from Sars 1895: pl. 122), i—N. pulchellus asiaticus ssp. nov., j—Shoemakeroides cornigerus (Shoemaker, 1964) (modified from Shoemaker 1964: fig. 9), k—Sh. gagarae (Gurjanova, 1972) (from Gurjanova 1972: fig. 16), l—Hendrycksopleustes neimanii sp. nov.

FIGURE 2. Neopleustinae Bousfield & Hendrycks, 1994, mouthparts: a–o—mandible; p–w—maxilla 1; x–ae—maxilla 2; a—Neopleustes boecki boecki (Hansen, 1888) (from Sars 1895: pl. 122), b, i, p, x—N. boecki pacifica ssp. nov., c, j, q, y—N. carinatus Margulis, 1963 (original image by author), d, k, r, z—N. columbianus Hendrycks & Bousfield, 2004 (from Hendrycks & Bousfield 2004: fig. 27), e, l, s, aa—N. pulchellus pulchellus (Krøyer, 1846) (from Sars 1895: pl. 122), f, m, t, ab—N. pulchellus asiaticus ssp. nov., u, ac—Shoemakeroides cornigerus (Shoemaker, 1964) (from Hendrycks & Bousfield 2004: fig. 30), g, m, v, ad—Sh. gagarae (Gurjanova, 1972) (from Gurjanova 1972: fig. 16), h, n, w, ae—Hendrycksopleustes neimanii sp. nov.

FIGURE 6. Hendrycksopleustes neimanii sp. nov., holotype, female: a—lateral view, b—cephalon dorsally, c—cephalon laterally, d, e—antenna 1, f—peduncle of antenna 2, g—upper lip, h—left mandible; paratype, male, 8.8 mm: i—antenna 2; scales: a—3 mm; b, c, d, f, i—1 mm; g, h—0.5 mm, e—0.1 mm.

FIGURE 22. Distribution of Neopleustinae species