Metadulichia kohtsukai Ariyama 2019, sp. nov.
Creators: name: Ariyama, Hiroyuki
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Dulichiidae
Metadulichia
Metadulichia kohtsukai

description: Metadulichia kohtsukai sp. nov.
(Figs 14–16)
[Japanese name: Hosonaga-shakutoridoronomi, new]
Material examined. Holotype: male (OMNH-Ar-10824), 3.5mm, Sagami Bay, southwest of Miura City, Kanagawa Prefecture, 35°06′57"N, 139°33′44"E– 35°06′43"N, 139°34′03"E (Fig. 1E), 230–398 m depth, using dredge, 10 December 2015, coll. H. Kohtsuka.
Diagnosis. Eyes ovate. Accessory flagellum 3-articulate. Maxilla 1 small, outer plate bearing 7 terminal robust setae, palp with 3 robust setae at tip. Maxilla 2 inner plate with single mediofacial seta. Male gnathopod 2, basis short, propodus massive, subovoid, posterior margin weakly setose, with small proximal and distal projections and small swelling. Pereopods 3, 4 bases slender. Pereopod 5 elongate, not prehensile. Urosomite 1 about 1.65 times as long as pleonites 2+3. Uropod 2 outer ramus very short, 17% as long as inner ramus.
Description of male [based on holotype (OMNH-Ar-10824), 3.5 mm]. Body (Fig. 14) smooth, dorsal margins with sparse short setae, urosomite 1 about 1.65 times as long as pleonites 2+3. Eyes ovate, about 35% length of head, composed of many tight ommatidia.
Antenna 1 (Fig. 15A, A 1) slender, about same length as body, posterior margin setose; length ratio of peduncular articles 1–3 1.0: 2.3: 2.8; accessory flagellum short, 3-articulate; primary flagellum with 6 articles, tip minute. Antenna 2 (Fig. 15B) slender, about 0.7 times as long as antenna 1, posterior margin setose; length ratio of peduncular articles 3–5 1.0: 7.5: 6.3; flagellum with 3 articles. Upper lip (Fig. 15C), ventral margin bare. Mandibles (Fig. 15D, D 1, E, E1) with length ratio of palp articles 1–3 1.0: 3.6: 2.0, articles 2, 3 bearing 5 and 3 setae, respectively; incisor with 4 cusps, lacinia mobilis with 3 cusps, 4 accessory blades present in both sides; molar with spatula-like process in right. Lower lip (Fig. 15F), outer plates with sparse setae apically. Maxilla 1 (Fig. 15G, G 1), outer plate with 7 robust setae distally, palp article 2 bearing 3 robust and 1 slender setae distally and 3 slender setae laterally. Maxilla 2 (Fig. 15H), inner plate with distal setae, very thin lateral setae and single mediofacial seta; outer plate bearing many setae on distal margin. Maxilliped (Fig. 15I), inner plate with 3 apical and 1 mediodistal short robust setae on ventral surface; outer plate bearing 5 robust setae mediodistally.
Gnathopod 1 (Fig. 16A) relatively slender; coxa with ventral notch; merus setose posterodistally and mediodistally; carpus longer than basis, with many setae on posterior margin; propodus slender, with many setae posteriorly, mediodistal surface heavily setose; dactylus long, slender, curved posteriorly. Gnathopod 2 (Fig. 16B, B 1), coxa subrectangular, ventral margin straight, gill small; basis short, anterodistal corner lobate; carpus setose posteriorly; propodus massive, subovoid, about 0.9 times as long as head, about 1.7 times length of carpus, posterior margin weakly setose, with short proximal projection at about 70° angle to palm, small distal projection at about 50° angle to palm and small swelling on distal side of proximal projection; dactylus curved posteriorly, posterior margin roundly produced proximally.
Pereopods 3, 4 (Fig. 16C, C 1, D) slender, pereopod 3 slightly longer than pereopod 4; coxae triangular, gills long; bases elongate, about 5.2 and 4.8 times as long as width respectively, each with glands in anterodistal and posteroproximal parts; propodi and dactyli narrow. Pereopod 5 (Figs 14, 16E, E 1) long; coxa triangular, gill small; basis–carpus with many short robust setae, carpus about 0.55 times as long as propodus; propodus lacking palm, anterior margin bearing 3 robust setae; dactylus long. Pereopods 6, 7 (Fig. 14) lost except for coxae.
Pleopods (Fig. 16 F–H), peduncles progressively longer, each with 2 slender coupling hooks; outer rami slightly longer than inner rami, outer rami with 7, 7, 6 articles respectively, inner rami each with 6 articles. Uropod 1 (Fig. 16I), peduncle with 3 lateral and 2 medial robust setae; outer ramus about 0.85 times as long as inner ramus (including distal robust setae), with 2 lateral, 1 medial and 2 distal (long and short) robust setae; inner ramus bearing 2 lateral, 4–5 medial and 2 distal (long and short) robust setae. Uropod 2 (Fig. 16D) about half length of uropod 1 (including distal robust setae); peduncle with 2 medial robust setae; outer ramus very short, 17% as long as inner ramus, without setae; inner ramus bearing 1–2 lateral and 2 medial robust setae. Telson (Fig. 16D) bare.
Female. Unknown.
Coloration in life. Unknown.
Etymology. Dedicated to Hisanori Kohtsuka of the University of Tokyo for donating many amphipod specimens and their photographs.
Habitat. Bottom sediment unknown, 230–398 m depth.
Distribution. Japan: Sagami Bay (present study).
description: Published as part of Ariyama, Hiroyuki, 2019, Four Species of Dulichiidae (Crustacea: Amphipoda) from Japan, with the Description of a New Genus and Two New Species, pp. 29-48 in Species Diversity 24 (1) on pages 44-47, DOI: 10.12782/specdiv.24.29, http://zenodo.org/record/4585163