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Paronesimoides calceolus sp. nov. (Figures 2 –6) Material examined Holotype. Male (6.8 mm), AMNH _IZC 00361497, the surface of the chimney named ‘Chim 4’ in the CH 3 site in the Shinkai Seep Field (Okumura et al. 2016), Mariana Trench (11.656°N, 143.048°E), 5689– 5683 m, collected by H.K. Watanabe, 17 July 2014. Paratype. Female (3.8 mm), AMNH _ IZC 00361498, data same as for the holotype. Diagnosis Lateral cephalic lobe of head rounded distally. Antenna 1 slightly longer than antenna 2. Peduncular article 3 of antenna 2 with strong posteroventral process. Male antennae 1 and 2 with calceoli. Mandibular palp article 3 0.8 times as long as article 2. Propodus of male gnathopod 1 length 1.2 times width, with two uneven-sized nodular robust setae on distal part of palmar margin. Coxa 4 with shallow posteroproximal concavity. Telson with two rows of dorsocentral short setae. Description Male [holotype, AMNH _ IZC 00361497]. Head (Figure 2) deeper than long; lateral cephalic lobe large and rounded distally; antennal sinus shallow and rounded; rostrum short; eyes absent. Pereonites 1–7 (Figure 2) dorsally smooth with fine setae. Pleonites 1–3 (Figure 2) without dorsal carina, bearing fine setae. Posterior margin of epimeral plates 1 and 2 (Figure 3a, b) rounded, each with a small seta. Posterodistal corner of epimeral plate 3 with small process accompanied by small seta. Urosomites 1–3 (Figure 2) without dorsolateral flange and notch. Antenna 1 (Figure 3d) short, 0.3 times as long as body; peduncular articles 1–3 rectangular, in length ratio of 1.0:0.6:0.2; length of peduncular article 1 1.5 times width; primary flagellum 17-articulate with calceoli (Figure 3e); accessory flagellum fivearticulate. Antenna 2 (Figure 3f) 0.9 times as long as antenna 1; posterior part of peduncular article 3 strongly produced; peduncular article 4 slightly longer than article 5; flagellum 15-articulate with calceoli. Upper lip (Figure 3g) with weakly concave ventral margin, bearing fine setae. Mandible (Figure 3h, i) with small incisor; lacinia mobilis a cuspidate peg; accessory setal row with two short plumose setae; molar with weakly triturative surface, not setose; mandibular palp three-articulate in length ratio of 1.0: 4.9: 3.8, attached opposite molar; palp article 1 bare, articles 2 and 3 with nine and 11 setae, respectively. Lower lip (Figure 3j) with broad outer lobes bearing fine setae, inner lobes indistinct. Maxilla 1 (Figure 3k) with inner plate bearing two setae apically; outer plate (Figure 3l) with 11 robust setae, seven of which obviously serrate; palp two-articulate, article 1 short, article 2 with seven robust setae along apical margin and slender seta on apical submargin. Maxilla 2 (Figure 3m) with narrow inner plate, bearing long plumose setae medially; outer plate slightly longer than inner plate. Maxilliped (Figure 4a) with rectangular inner plate with two nodular and two small robust setae apically (Figure 4b), oblique setal row with nine plumose setae; outer plate ovate with nodular robust setae along apical to medial margin (Figure 4c); palp fourarticulate, article 1 with seta on outer margin, article 2 longest with seta on outer margin and setal row on inner margin, article 3 with setae on inner and outer margins and fine facial setae, article 4 with fine facial setae, nail distinct. Gnathopod 1 (Figure 4d) subchelate; coxa broad, bearing setae along anterior to ventral margin; basis weakly arched, length 3.3 times width, with setae on anterior and posterior margins; ischium short, length 1.4 times width, with seta on posterior margin, posterodistal corner with pair of setae; merus with five setae on posterior margin; carpus length 1.1 times width; propodus rectangular, length 1.2 times width, posterior margin weakly convex with a few setae, palmar margin (Figure 4e) transverse, waved, with two nodular robust setae distally; dactylus (Figure 4e) slightly exceeding distal part of palm, with seta on anterior margin and three setae on mediodistal surface. Gnathopod 2 (Figure 4f) minutely chelate; coxa subrectangular bearing setae along anterior to ventral margin; basis straight, length 4.3 times width, with setae on anterior and posterior margins; ischium relatively long, length 2.3 times width, with setae on anterior and posterior margins, posterodistal corner with cluster of setae, laterodistal surface with patch of tiny setae; merus with five setae on ventral margin, ventral surface with tiny setae; carpus length 2.6 times width, dorsal and ventral surfaces with tiny setae; propodus length 1.4 times width, surface covered with tiny setae, lateroventral surface with palmate setae, palmar margin (Figure 4g) weakly convex with serration, posterodistal corner of palmar margin with two medial robust setae; dactylus (Figure 4g) short, not reaching posterodistal corner of palmar margin, with seta on anterior margin and four setae on lateral surface. Pereopod 3 (Figure 4h) with subrectangular coxa bearing setae along anterodistal to ventral margin; lateral surface of merus and carpus with tiny setae; propodus with five robust setae along posterior margin, posterodistal corner with pair of robust setae; dactylus (Figure 4i) slender. Pereopod 4 (Figure 5a) with broad coxa bearing setae along anterodistal to ventral margin, posteroproximal part with wide, shallow concavity; lateral surface of merus and carpus with tiny setae; propodus with five robust setae along posterior margin, posterodistal corner with pair of robust setae; dactylus slender. Pereopod 5 (Figure 5b) with equilobate coxa; basis weakly expanded, length 1.4 times width, with long setae along anterior margin, posterior margin slightly crenate with short setae; merus and carpus without setae on posterior margin, posterodistal corner with robust seta; propodus with five robust setae along anterior margin, anterodistal corner with pair of robust setae; dactylus slender. Pereopod 6 (Figure 5c) with small coxa, anterior lobe reduced, posterior lobe broad; basis length 1.7 times width, with long setae on anterodistal margin, posterior margin slightly crenate with short setae; merus and carpus each with robust seta on posterior margin and posterodistal corner, respectively; propodus with five robust setae along anterior margin, anterodistal corner with pair of robust setae; dactylus slender. Pereopod 7 (Figure 5d) with small coxa, subtriangular; basis expanded posteriorly, length 1.4 times width, with long setae on anterodistal margin, posterior margin slightly crenate with short setae; merus with two robust setae on posterior margin and robust seta on posterodistal corner; carpus with robust seta on posterior margin and posterodistal corner; propodus with four robust setae along anterior margin, anterodistal corner with pair of robust setae; dactylus slender. Coxal gills on gnathopod 2 and pereopods 3–6 (Figure 2). Pleopods 1–3 (Figure 5e) with broad peduncle, with setae along lateral margin, mediodistal margin with paired retinacula (Figure 5f). Uropod 1 (Figure 5g, h) with peduncle bearing four dorsolateral, one apicolateral, four dorsomedial and one apicomedial robust setae; inner ramus 0.8 times as long as peduncle, with two dorsal robust setae; outer ramus 1.1 times as long as inner ramus, with three dorsal robust setae. Uropod 2 (Figure 5i) with peduncle bearing two dorsolateral, one apicolateral, one apicomedial and one distoventral robust setae; inner ramus 0.8 times as long as peduncle, with dorsal robust seta; outer ramus slightly shorter than inner ramus, with two dorsal robust setae. Uropod 3 (Figure 5j) with peduncle 1.2 times as long as outer ramus, with robust setae distally; inner ramus small, scale-like, 0.1 times as long as outer ramus, with apical seta; outer ramus two-articulate, proximal article marginally bare, with two distal setae, distal article 0.3 times as long as proximal article. Telson (Figure 5k) semicircular, distal margin smooth, length 0.9 times width, with four lateral penicillate setae, two rows of dorsocentral short setae and two distal simple setae. Female [paratype, AMNH _ IZC 00361498]. Antenna 1 (Figure 6a) peduncular articles 1–3 rectangular, in length ratio of 1.0:0.5:0.4; length of peduncular article 1 1.3 times width; primary flagellum nine-articulate without calceoli; accessory flagellum three-articulate. Antenna 2 (Figure 6b) 0.7 times as long as antenna 1; flagellum seven-articulate without calceoli. Gnathopod 1 (Figure 6c, d) chelate; coxa weakly tapering; propodus length 2.6 times width, mediodistal part of palm with two curved robust setae, palmar margin minutely serrate; dactylus slightly exceeding distal part of palm. Gnathopod 2 (Figure 6e, f) similar to that of male, carpus length 2.0 times width. Etymology The new specific name is derived from the presence of calceoli on male antennae 1 and 2. Remarks Paronesimoides calceolus sp. nov. differs from its congeners with respect to the following features: from P. lignivorous (features of P. lignivorous in parentheses): the cephalic lobe of the head is rounded (pointed); antenna 2 has the peduncular article 3 with a posteroventral process (lacking a process); mandibular palp article 3 is 0.8 times as long as article 2 (0.6 times); length of propodus of gnathopod 1 is 1.2 times its width (1.6 times); and posteroproximal concavity of coxa 4 is shallow (deep); from P. voightae (features of P. voightae in parentheses), the cephalic lobe of the head is rounded (pointed); antenna 1 is longer than antenna 2 (almost the same length); antennae have calceoli in male (absent); two nodular robust setae on the distal part of the palmar margin of gnathopod 1 are of uneven size (even-sized); coxa 2 does not cover the ventral margin of coxa 1 (most of the posteroventral margin covered by coxa 2); and telson has two rows of dorsocentral short setae (absent). Distribution Known only from the type locality. Key to species of Paronesimoides (male) 1. Antenna 2 peduncular article 3 with strong posteroventral process............................. 2 - Antenna 2 peduncular article 3 without strong posteroventral process.................................................................................................................................................. P. lignivorous Pirlot, 1933 2. Cephalic lobe of head pointed; antennae without calceoli; most of posteroventral margin of coxa 1 covered by coxa 2.............................................. P. voightae Larsen, 2007 - Cephalic lobe of head rounded; antennae with calceoli; ventral margin of coxa 1 not covered by coxa 2.......................................................................................... P. calceolus sp. nov., Published as part of Tomikawa, Ko, Watanabe, Hiromi Kayama, Tanaka, Katsuhiko & Ohara, Yasuhiko, 2022, Discovery of a new species of Paronesimoides (Crustacea: Amphipoda: Tryphosidae) from a cold seep of Mariana Trench, pp. 463-474 in Journal of Natural History 56 (5 - 8) on pages 465-473, DOI: 10.1080/00222933.2022.2074906, http://zenodo.org/record/7012392, {"references":["Okumura T, Ohara Y, Stern RJ, Yamanaka T, Onishi Y, Watanabe H, Chen C, Bloomer SH, Pujana I, Sakai S, et al. 2016. Brucite chimney formation and carbonate alteration at the Shinkai Seep Field, a serpentinite-hosted vent system in the southern Mariana forearc. Geochem Geophys Geosyst. 17 (9): 3775 - 3796. doi: 10.1002 / 2016 GC 006449.","Pirlot JM. 1933. Les amphipodes de l'expedition du Siboga, deuxieme partie, Les amphipodes gammarides, II: les amphipodes de la mer profonde, 1 (Lysianassidae, Stegocephalidae, Stenothoidae, Pleustidae, Lepechinellidae). Sibog Exp Monogr. 33 c: 115 - 167.","Larsen K. 2007. Amphipoda (Crustacea; Peracarida) from the hydrothermal vent system of the Juan De Fuca Ridge, Escabana trough and Gorda ridge, northeast Pacific. Part I. Lysianassidae and Sebidae Zootaxa. 1445 (1): 1 - 26. doi: 10.11646 / zootaxa. 1445.1.1."]}

Tomikawa, Ko, Watanabe, Hiromi Kayama, Tanaka, Katsuhiko, Ohara, Yasuhiko (2022): Discovery of a new species of Paronesimoides (Crustacea: Amphipoda: Tryphosidae) from a cold seep of Mariana Trench. Journal of Natural History 56 (5-8): 463-474, DOI: 10.1080/00222933.2022.2074906, URL: http://dx.doi.org/10.1080/00222933.2022.2074906

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