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 Author Labay, Vjacheslav S. text Zootaxa 2021 2021-05-20 4974 2 267 306 journal article 6360 10.11646/zootaxa.4974.2.3 ba9eadc3-7247-4841-8272-e7af87754011 1175-5326 4775545 B4D51BEC-2B48-4B77-A49B-6D5949EDAA99 Neopleustes boecki pacifica ssp. nov. Figures 1b , 2b, I, p, x , 3a , 4b , 5b , 12–13 , 22 Diagnosis . Female ( 9 mm ). Body, pereon segments 1–6 without carination, strongly carinated posteriorly from segment 7 to pleon segment 2, pleon segment 3 with sloping low ridge dorsally. Pereonal and pleonal segments with submedial and sublateral groups of plumose aesthetascs dorsally. Head with anterodorsal crest. Rostrum medium, about 0.5 times as long as peduncular segment 1 of antenna 1, apex acute; anterior head lobe rounded, lateral cephalic lobe very deeply recessed sinus, anteroventral corner acute. Eye large, subrounded, pigmented. Antenna 1 very long, slightly shorter than body length; peduncular segment 1 elongate and strong, equal to segments 2 and 3 together; flagellum length about 4 times as long as peduncle, with 65 articles, articles posterodistally with aesthetascs and short setae. Antenna 2 is 0.5 times as antenna 1 length, flagellum with 43 articles. Upper lip apically bilobate and asymmetrical. Lower lip, outer lobes rounded, widely spread. Mandible, molar weak, bare, without a medial molar seta; incisor margins with 7–9 teeth; left lacinia 10-dentate, right lacinia absent; accesory spine rows with 7–9 raker setae; palp very large; palp segment 3 subequal to segment 2, inner margin lined with strong pectinate D setae, apex with 2 long and one medium strong pectinate E setae; segment 2, inner margin with few setae only; segment 1 without setae. Maxilla 1, inner plate with single plumose apical seta; outer plate with 9 slender pectinate setae (spine-like setae); palp extending beyond outer plate, apex subtruncate, with a row of 7 cuspidate setae ( Watling, 1989 : type IIA3) and with a row of 7 subapical thin setae. Maxilla 2, inner plate slightly shorter and broader than outer plate; inner margin with single strong plumose seta. Maxilliped, inner plate very short, not reaching the basal article of palp, apex subtruncate, with 2–3 button setae ( Watling, 1989 : type IIA4) and a few slender setae; outer plate short, reaching about 0.25x length of palp segment 2, apex narrowly subtruncate; palp narrow, segment 2 subequal in legth to segment 3; dactylus slender, slightly curved and slightly shorter than palp segment 3, the distal process of palp segment 3 is present buy not conspicuous. Coxal plates 1–3 posteroventrally minutely multi-cuspate, lower margins rounded; coxal plate 4 much broader, deeply excavated posteroproximally, rounded below; coxal plates 5–6 broadly posterolobate, posteriorly roundly subquadrate, coxal plate 7 trapezoidal, rounded anteroventrally, with rectangular posterodistal angle. Coxal gills relatively small, sac-like. Pereopods 1 and 2 (gnathopods 1 and 2) small, weakly subchelate, subsimilar. Pereopod 1, basis with rare anterior setae, carpus long, about 0.8 times as long as propodus, posterior lobe broad, shallow; propodus subrectangular, narrow, palm oblique, with small mid-palmar tooth, with 2 clusters of spine-like setae; posterior margin with 2–3 groups of setae. Pereopod 2, merus without posterodistal tooth, carpus long, about 0.71 times as long as propodus, carpal lobe as in pereopod 1, palmar margin with medial tooth and with 2 clusters of strong posterodistal spineformes setae, posterior margin with 4 transversal setae clusters. Pereopods 3–4 medium strong; basis linear, with short setae along anterior and posterior margins; merus anterodistally produced, acute; carpus 1.4 times shorter than merus, posterior margin with 4 groups of strong spine-like setae; propodus 1.2–1.4 times as long as carpus, posterior margin with 7 groups of strong spine-like setae; dactylus slender, 0.63 times as long as propodus. Pereopods 5–7 closely homopodous in form and size; bases with posterior rounded wing; merus posterodistally produced, acute, anterior margin with 5–6 groups of strong spine-like setae, posterior margin with 5 groups of strong setae; carpus 1.4 times shorter than merus, anterior margin with 4 groups of strong spine-like setae; propodus 1.3 times as long as carpus, anterior margin with 6 groups of strong spine-like setae; dactylus medium in length, 0.67 times as long as propodus. Epimeral plates 1–3, lower margin with short spine-like setae, posteroventral corners acute, slightly produced, posterior margin minutely serrated. Pleopods regular, coupling basis of inner ramus with 4 specific stout twopointed plumose setae. Uropod 1, peduncle slightly shorter than inner ramus; outer ramus the shorter; margins of peduncle and rami with serially arranged short spine-like setae. Uropod 2, inner ramus 1.7 times as long as peduncle, outer ramus the shorter, 0.63 times as long as inner. Uropod 3, inner ramus 3 times as long as peduncle, with a row of 6–7 small spine-shaped setae along lateral and medial margins each, with acute and non-setae 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-setae apex. Telson linguiform, apically rounded, length about 1.65x width, with proximal ventral keel, with lateral and subapical paired short setae. Male: unknown. Type material . Holotype , female, 9 mm , Х 53862 /Cr-2407, Sea of Okhotsk , Far East of Russia ( 51°31′ N 143°48′36 E , 88 m ), pebbles with sands and silt, 12 October 2017 . Paratypes : 1 female , Х 53863 /Cr-2408, 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 .; 9 females , Х 53864 /Cr-2409, Sea of Okhotsk , Far East of Russia (54 T ; 659116 E, 5205062 N, 5–20 m ), rocks, 11 July 2019 . Type locality . The eastern coast of Sakhalin Island , Sea of Okhotsk , Far East of Russia ( 51°31′ N 143°48′36 E , 88 m ) . Etymology . Named after the type locality in Pacific Ocean. The name is masculine in gender. Ecology : Neopleustes boecki pacifica was found at the depth of 88 m on the pebbles with sands and silt bottom in the layer of constant low temperature (-1.2—+0.5°C). Female with developed marsupium was found in October. It is found on the shelf of south-eastern Sakhalin Island and in the Gulf of Aniva at a depth of 5–20 m on rocky and stony ground. Distribution : The shelf of eastern Sakhalin Island. Remarks . Neopleustes boecki pacifica ssp. nov. is morphologically identical to the nominotypical subspecies Neopleustes boecki ( Hansen, 1887 ) ( Gurjanova 1951 ; Hansen 1887 ; Hendrycks & Bousfield 2004 ; G. Sars 1895 ; Stebbhing 1906). Neopleustes boecki pacifica differs from N. boecki only by the presence of submedial and sublateral groups of plumose aesthetascs dorsally on pereonal & pleonal segments ( Figs. 1b , 12a ).