Commensal Leucothoidae (Crustacea, Amphipoda) of the Ryukyu Archipelago, Japan. Part II: sponge-dwellers Author White, Kristine N. Author Reimer, James Davis text ZooKeys 2012 166 1 58 http://dx.doi.org/10.3897/zookeys.166.2313 journal article http://dx.doi.org/10.3897/zookeys.166.2313 1313-2970-166-1 Leucothoe nagatekubi sp. n. Figures 1112 Type material. Holotype male, 3.0 mm RUMF-ZC-1768, Mizugama, Okinawa-jima Island, Okinawa, reef wall ( 26°21'35"N , 127°44'22"E ), in canals of orange encrusting sponge , Clathria of Schmidt 1862 , 10 m, N.S. White, col., 26 February 2011 (KNWOkinawa34K). Paratype female, 3.4 mm RUMF-ZC-1769, Mizugama, Okinawa reef wall ( 26°21'35"N , 127°44'22"E ), in canals of orange encrusting sponge, Clathria , 7 m, N.S. White, col., 20 October 2011 (KNWOkinawa69D) Type locality. Mizugama, Okinawa-jima Island, Okinawa, Japan ( 26°21'35"N , 127°44'22"E ). Additional material examined. 9 specimens, NSMT-Cr 21896, KNWOkinawa69B; 9 specimens, RUMF-ZC-1770, KNWOkinawa69C. Diagnosis (male). Head anterior margin truncate, anterodistal margin quadrate with cusp. Maxilla 1 palp 1-articulate. Maxilliped outer plate tuberculate with facial setae. Gnathopod 1 basis anterodistal margin with 7 very short, slender setae. Gnathopod 2 carpus elongate, distally tapered; propodus palm with large concavity. Pereopod 7 basis posteriorly serrate. Telson with plumose facial setae. Description (male). Head. Anterior margin truncate, anterodistal margin quadrate with cusp; ventral cephalic keel anterior margin transverse, anteroventral margin quadrate, ventral margin distally excavate, rounded; eyes with more than 10 ommatidia, round. Antenna 1 0.3 x body length, flagellum 7-articulate, peduncle article 1 width less than 2 x article 2, accessory flagellum 1-articulate. Antenna 2 0.3 x body length, subequal in length with antenna 1, flagellum 4-articulate. Mandibular palp ratio of articles 1-3 1.0: 3.0: 1.7, article 2 with 2 medium distal setae, article 3 with 2 distal setae, incisors strongly dentate; left mandible with 5 raker spines, lacinia mobilis large, strongly toothed; right mandible with 7 raker spines, lacinia mobilis small, strongly dentate. Upper lip asymmetrically lobate, anterior margin setose. Lower lip inner lobes fused, bare; outer lobes with moderate gape, anterior margins setose. Maxilla 1 palp 1-articulate with 4 distal setae; outer plate with 5 distal robust setae. Maxilla 2 inner plate with 3 robust distal setae and 7 slender marginal setae; outer plate with 3 robust distal setae and 15 slender distal marginal setae. Maxilliped inner plates distal margin with a v-shaped indentation, with short robust setae; outer plate inner margin tuberculate, reaching 0.1 x palp article 1, with simple marginal setae, facial setae present; palp article 4 subequal in length with article 3, distally acute. Pereon. Coxae 1-4 relative widths 1.0: 1.8: 1.1: 2.1. Gnathopod 1 coxa smooth, with tiny marginal setae, anterodistal margin produced, rounded with cusp, distal margin straight, posterior margin excavate, facial setae absent; basis linear, anterodistal margin with 7 very short, slender setae, posterior margin bare; ischium bare; carpus linear, distal length 13.1 x width, proximal margin serrate, distal margin with 1 short seta; propodus straight, palm with 6 distal triangular teeth and 6 distal setae; dactylus smooth, reaching 0.1 x propodus length. Gnathopod 2 coxa broader than long, subequal in size with coxa 3, smooth, with tiny marginal setae, anterior margin expanded anteriorly, anterodistally rounded, distal margin oblique, posterior margin straight, facial setae absent; basis distally expanded, anterior margin with 5 medium setae, distal margin with 2 setae, posterior margin with 3 setae; ischium with 3 posterior, 2 distal, and 3 posterodistal setae; carpus 0.5 x propodus length, curved, distally tapered, anterior margin smooth; propodus with 1 mediofacial setal row above midline, reaching 0.8 x propodus length, with 2 submarginal setae, posterior margin smooth, palm convex with 6 major tubercles and 1 major concavity; dactylus curved, proximal margin smooth with 1 seta, anterior margin distally acute, reaching 0.5 x propodus length. Pereopod 3 coxa length 1.5 x width, anterodistal corner overriding distal face of coxa 2 and extending below it, smooth, with tiny marginal setae, anterior margin evenly rounded, distal margin oblique, posterior margin straight, facial setae absent. Pereopod 4 coxa smooth, with tiny marginal setae, anterior margin produced, distal margin evenly rounded, posterior margin tapered, facial setae absent. Pereopods 5-7 coxae facial setae absent; bases width length ratios 1: 1.3, 1: 1.3, 1: 1.2, posterior margins setose. Pereopods 5-6 bases posterior margins smooth, pereopod 7 basis posterior margin serrate. Pleon. Epimera 1 and 3 bare, epimeron 2 with ventral setae; epimeron 3 posteroventral corner rounded. Uropods 1-3 relative lengths 1.0: 0.7: 0.9. Uropod 1 peduncle and outer ramus subequal in length with inner ramus; inner ramus with 5 robust setae and outer ramus with 2 robust setae. Uropod 2 peduncle 0.9 x inner ramus length, outer ramus 0.7 x inner ramus length; inner ramus with 1 robust seta and outer ramus with 2 robust setae. Uropod 3 peduncle 1.6 x inner ramus length, outer ramus 0.9 x inner ramus length; inner ramus with 1 robust seta and outer ramus with 2 robust setae. Telson 2.3 x longer than wide, with plumose facial setae, apex strongly tridentate. Female (sexually dimorphic characters). Unknown. Figure 11. Leucothoe nagatekubi sp. n., holotype male, 3.0 mm, RUMF-ZC-1768. Figure 12. Leucothoe nagatekubi sp. n., holotype male, 3.0 mm, RUMF-ZC-1768; paratype female, 3.4 mm, RUMF-ZC-1769. Etymology. After the Japanese words 'nagai' , meaning 'long' , and 'tekubi' , meaning 'wrist' and referring to the elongate carpus on gnathopod 2. (Pronounced na-ga-tay-koo-bee) Ecology. In canals of orange encrusting sponge, Clathria sp., RUMF-ZP-5, KNWOkianawa69G (Figure 25D), found in caves. Relationships. Leucothoe nagatekubi sp. n. is similar to Leucothoe serrata White & Thomas, 2009 in having an elongate gnathopod 2 carpus, narrow gnathopod 1 propodus and carpus, high mediofacial setal row on gnathopod 2 propodus, and wide pereopod 5-7 bases. It differs in the large indentation on the gnathopod 2 propodus palm, having a 1-articulate accessory flagellum on antenna 1, triangular teeth on gnathopod 1 propodus palm, and a 1-articulate maxilla 1 palp. Remarks. Leucothoe nagatekubi sp. n. is pinkish-orange in color (Figure 24C). This species is endemic to the western coast of Okinawa-jima Island, Okinawa. Distribution. East China Sea: Okinawa-jima Island, Okinawa, Japan.