Paranamixis lunata, White & Machida, 2018

White, Kristine N. & Machida, Ryuji J., 2018, Taiwanese Leucothoidae (Crustacea: Amphipoda), Including Three New Species from Dongsha Atoll., Zoological Studies 57 (47), pp. 1-22 : 15-19

Paranamixis lunata sp. nov.

( Figs. 3 H-I, 8-9)

urn:lsid:zoobank.org:act:922F45BF-FC20-4E79-A088-5E9044AAEC3A

Material examined: Holotype: male anamorph, 2.6 mm, NMMB-CD 5587 , KNW-Dongsha-2017-7a, Dongsha Atoll, northeast fore reef, 20°46'52.26"N, 116°45'51.50"E, 17.8 m; 23 May 2017; K.N. White, collector . Paratypes: male leucomorph, 1.9 mm, NMMB-CD 5588, same station data as Holotype; female leucomorph, 2.1 mm, NMMB-CD 5589, KNW-Dongsha-2017-9a, Dongsha Atoll, northeast fore reef, 20°46'52.11"N, 116°48'10.81"E, 17.7 m; 24 May 2017; K.N. White, collector.

Other: 5 anamorph males, 2 leucomorph males, 9 leucomorph females; KNW-Dongsha- 2017 - 1 b, f Dongsha Atoll north beach, 20°42'18.26"N, 116°43'43.29"E, 1.5 m; 29 May 2017; K.N. White, collector. 1 leucomorph female; KNW-Dongsha-2017- 3m, Dongsha Atoll lagoon, 20°42'14.76"N, 116°48'17.2074"E, 11 m; 21 May 2017; K.N. White, collector. 1 anamorph male, 1 leucomorph female; KNW-Dongsha-2017-10b, Dongsha Atoll southwest fore reef, 20°35'58.45"N, 116°45'05.55"E, 12 m; 26 May 2017; K.N. White, collector. 1 anamorph male, 1 leucomorph male, 3 leucomorph females, 2 leucomorph juveniles; ASIZCR000423, KNW-Dongsha-2017-11a, Dongsha Atoll southwest lagoon, 20°39'32.00"N, 116°45'14.68"E, 5 m; 26 May 2017; K.N. White, collector. 4 anamorph males, 1 leucomorph male, 9 leucomorph females, 5 leucomorph juveniles; KNW-Dongsha-2017-12a,b, Dongsha Atoll south beach, 20°47'57.48"N, 116°43'24.07"E, 1.7 m; 27 May 2017; K.N. White, collector.

Etymology: From the Latin ‘ lunatus ’ meaning ‘shaped like a crescent moon’ in reference to the crescent-shaped ventral cephalic keel in male anamorphs of this species.

Diagnosis: Head anterior margin rounded with anterodistal cusp. Ventral cephalic keel concave, crescent-shaped ( Fig. 8B ). Gnathopod 2 coxa with midventral notch ( Fig. 8A ); basis with anteroproximal and mediodistal serrate ridges; propodus palm convex ( Fig. 8G ).

Description (male anamorph holotype): Head: Anterior margin rounded, anterodistal margin with cusp, distal margin slightly rounded; ventral cephalic keel anterior margin concave, anteroventral margin with sharp point, ventral margin oblique; eyes present with more than 10 ommatidia, round ( Fig. 8B ).

Antenna 1 0.4 × body length, flagellum 8-articulate, peduncle article 1 width less than 2 × article 2, accessory flagellum absent. Antenna 2 0.3 × body length, shorter than antenna 1, flagellum 3-articulate ( Fig. 8A ). Mouthparts reduced. Maxilliped inner and outer plates smooth, lacking inner lobes; palp 4-articulate, palp article 4 elongate, slender, strongly recurved ( Fig. 8H ).

Pereon: Coxae 1-4 relative widths 1.0: 1.7: 1.6: 1.9 ( Fig. 8A ).

Gnathopod 1 coxa reduced, smooth, bare. Gnathopod 1 absent. Gnathopod 2 coxa longer than broad, subequal in width with coxa 3, smooth, bare, anterior margin rounded, distal margin rounded with midventral notch ( Fig. 8A ); basis with anteroproximal and mediodistal serrate ridges, anterior margin with two short setae, posterior margin bare; carpus 0.8 × propodus length, curved, distally tapered, anterior margin smooth; propodus with 1 mediofacial setal row reaching 0.6 × propodus length, 1 submarginal setal row of five setae, posterior margin smooth, palm convex, with one large and several small triangular protrusions and small setae; dactylus curved, reaching 0.5 × propodus length, proximal margin with excavation and two long setae, anterior margin distally tapered, sub-acute ( Fig. 8G ).

Pereopod 3 coxa length 1.3 × width, anterodistal corner overriding distal face of coxa 2, with postero-distal notch, anterior and posterior margins straight, distal margin rounded. Pereopod 4 coxa smooth, anterior margin rounded, distal margin rounded, posterior margin convex. Pereopods 5-7 coxae, facial setae absent. Pereopods 5-7 bases width: length ratios 1: 1.1, 1: 1.2, 1: 1.2, pereopods 5-6 posterior margins smooth, bare; pereopod 7 posterior margin serrate, setose ( Fig. 8A ).

Pleon: Epimera 1-3 bare, epimeron 2 posteroventral corner with notch, epimeron 3 posteroventral corner quadrate with slight projection. Uropods 1-3 relative lengths 1.0: 0.8: 0.9. Uropod 1 peduncle 0.9 × inner ramus length, outer ramus 0.5 × inner ramus length; inner ramus with 3 robust setae; outer ramus with 2 robust setae ( Fig. 8E ). Uropod 2 peduncle 0.7 × inner ramus length, outer ramus 0.7 × inner ramus length; inner ramus with 4 robust setae; outer ramus with 2 robust setae ( Fig. 8D ). Uropod 3 peduncle subequal in length with inner ramus, outer ramus 0.8 × inner ramus length; inner ramus with 2 robust setae; outer ramus with 3 robust setae ( Fig. 8C ). Telson 1.4 × longer than wide, apex rounded, beset with 2 small setae ( Fig. 8F ).

Description (female and male leucomorph): Head: Anterior margin truncate, anterodistal margin subquadrate, distal margin straight; eyes present with about 20 ommatidia, round. Antenna 1 0.3 × body length, flagellum 7-articulate, peduncle article 1 less than 2 × width of article 2, accessory flagellum absent. Antenna 2 0.2 × body length, shorter than antenna 1, flagellum 3-articulate ( Fig. 9A ). Mandibles lost. Maxilla 1 palp 2-articulate, with 3 distal slender setae ( Fig. 9C ); outer plate lost. Maxilla 2 inner and outer plates each with 2-3 distal slender setae. Maxilliped outer plate vanishing; palp 4-articulate, article 4 subequal in length with article 3, distally acute ( Fig. 9I ).

Pereon: Coxae 1-4 relative widths 1.0: 0.8: 0.7: 1.0 ( Fig. 9A ).

Gnathopod 1 coxa smooth, distally expanded, anterior and distal margins rounded, posterior margin straight ( Fig. 9A ); basis long and smooth, anterior and posterior margins bare; ischium bare; carpus straight, distally thin, length 11 × width ( Fig. 9E ), proximal margin serrate ( Fig. 9F ); propodus narrowing distally, palm irregularly serrate with 4 large 4 small marginal setae; dactylus minute ( Fig. 9G ). Gnathopod 2 coxa longer than broad, wider than coxa 3, smooth, anterior margin straight, anterodistal margin rounded, distal margin nearly straight, posterior margin straight ( Fig. 9A ); basis expanded distally, anterior margin with few short setae, posterior margin with 1 seta; ischium with one postero-distal seta; carpus 0.3 × propodus length, straight, distally tapered, distal margin serrate, setose; propodus with 1 short mediofacial setal row, with row of submarginal setae, posterior margin smooth, posterior margin triangular ( Fig. 9D ), palm with triangular tubercles ( Fig. 9H ); dactylus strongly curved, distally acute, margins smooth, bare ( Fig. 9D ).

Pereopod 3 coxa length 1.8 × width, anterodistal corner overriding distal face of coxa 2, smooth, anterior margin straight, distal margin slightly rounded, posterior margin straight. Pereopod 4 coxa smooth, anterior margin rounded, distal margin rounded, posterior margin tapered. Pereopods 5-7 bases width length ratios 1: 1.2, 1: 1.1, 1: 1, posterior margins rounded, serrate, pereopods 5-6 posterior margins bare; pereopod 7 posterior margin setose ( Fig. 9A ).

Pleon: Epimera 1-3 bare, epimeron 3 posteroventral corner quadrate, with slight projection.

Uropods 1-3 relative lengths 1.0: 0.8: 1.1. Uropod 1 peduncle 0.7 × inner ramus length, outer ramus 0.4 × inner ramus length; inner ramus with 3 robust setae; outer ramus with 1 robust seta. Uropod 2 peduncle 0.6 × inner ramus length, outer ramus 0.8 × inner ramus length; inner ramus with 2 robust setae; outer ramus bare. Uropod 3 peduncle 0.8 × inner ramus length, outer ramus 0.7 × inner ramus length; inner and outer rami each with 1 robust seta ( Fig. 9A ). Telson 1.4 × longer than wide, bare, apex rounded ( Fig. 9B ).

Color pattern: When alive male anamorphs of this species are translucent with brown coloration on pereon segments 2-7, brown eyes, and an opaque ivory gnathopod ( Fig. 3H ); male and female leucomorphs are translucent with faint pink stripes on pereonite segments 2-5 and a red eye ( Fig. 3I ).

Ecology: This species was collected among Halimeda and coral rubble.

Relationships: Male anamorphs of Paranamixis lunata sp. nov. resemble P. bocki Schellenberg, 1938 , P. clarkae Thomas, 1997 , P. fijiensis Thomas, 1997 , and P. ledoyeri Ortiz and Lalana, 1997 in having an anteroventral cusp on the head and an excavate ventral cephalic keel. Paranamixis lunata sp. nov. differs in the unique crescent shape of the keel. Except for L. ledoyeri , all of these species have a serrate ridge on the anterior margin of gnathopod 2 basis, with the new species having both anteroproximal and mediodistal serrate ridges. Leucomorphs are unknown for all of the similar species.

Distribution: Dongsha Atoll, Taiwan (this study).

Figures

Fig. 3. (A) Leucothoe obuchii White and Reimer, 2012a, male, KNW-Green-2B; (B) Leucothoe ouraensis White and Reimer, 2012b, female, KNW-Dongsha-2017-10c; (C) Leucothoe togatta White and Reimer, 2012b, male, KNW-Dongsha-2017-7d; (D) Leucothoe toribe White and Reimer, 2012b, female, KNW-Dongsha-2017-6b; (E) Leucothoe trulla White and Reimer, 2012a, male, KNW-Dongsha-2017- 8a; (F) Leucothoe batillum sp. nov., male, KNW-Dongsha-2017-3f; (G) Leucothoe cracentis sp. nov., female, KNW-Dongsha-2017-4b; (H) Paranamixis lunata sp. nov., male anamorph, KNW-Dongsha-2017-7a; (I) Paranamixis lunata sp. nov., female leucomorph, KNW- Dongsha-2017-9a.

Fig. 8. Paranamixis lunata sp. nov. male anamorph holotype, scale bars represent 0.1 mm; (A) Habitus; (B) Head; (C) Uropod 3; (D) Uropod 2; (E) Uropod 1; (F) Telson; (G) Gnathopod 2 medial; (H) Maxilliped.

Fig. 9. Paranamixis lunata sp. nov. female leucomorph paratype, scale bars represent 0.1 mm; (A) Habitus; (B) Telson; (C) Maxilla 1 palp; (D) Gnathopod 2 medial; (E) Gnathopod 1 medial; (F) Gnathopod 1 carpus enlarged; (G) Gnathopod 1 propodus enlarged; (H) Gnathopod 2 propodus enlarged; (I) Maxilliped.