Leucothoe chiisainame, White, Kristine N. & Reimer, James Davis, 2012

White, Kristine N. & Reimer, James Davis, 2012, Commensal Leucothoidae (Crustacea, Amphipoda) of the Ryukyu Archipelago, Japan. Part III: coral rubble-dwellers, ZooKeys 173, pp. 11-50 : 25-28

Leucothoe chiisainame sp. n. Figures 7, 8

Type material.

Holotype female, 4.2 mm RUMF-ZC-1874, Kurio, Yakushima Island, Kagoshima, reef wall (30°16'00"N, 130°24'55"E), among coral rubble, 7-10 m, K.N. White and N.S. White, col., 26 May 2011 (KNWYaku1J).

Type locality.

Kurio, Yakushima Island, Kagoshima, Japan (30°16'00"N, 130°24'55"E).

Additional material examined.

No additional material available for examination.

Diagnosis (female).

Head anterior margin excavate; ventral cephalic keel anterior margin excavate, anteroventral margin produced, rounded; eyes small. Antenna 1 accessory flagellum 1-articulate. Right mandible lacinia mobilis with 2 rows of dentition. Maxilla 2 inner plate with 3 rows of 2, 2, and 3 distal setae, with 3 marginal setae. Maxilliped inner plates with wide v-shaped indentation distally. Gnathopod 1 coxa anterodistally serrate; propodus palm with square-shaped dentition. Gnathopod 2 carpus distally truncate. Pereopods 5-6 coxae with facial setae. Pereopods 5-7 bases broadly expanded, posteriorly serrate. Epimeron 1 with 1 anteroventral seta.

Description (female).

Head. Anterior margin excavate, anterodistal margin rounded, distal margin straight; ventral cephalic keel anterior margin excavate, anteroventral margin produced, rounded, ventral margin convex; eyes present with more than 10 ommatidia, round, small. Antenna 1 0.3 × body length, flagellum 7-articulate, peduncle article 1 width less than 2 × article 2, accessory flagellum 1-articulate. Antenna 2 0.2 × body length, shorter than antenna 1, flagellum 4-articulate. Mandibular palp broken in dissection, incisors strongly dentate; left mandible with 9 raker spines, lacinia mobilis large, strongly toothed; right mandible with 11 raker spines, lacinia mobilis small with 2 rows of dentition. Upper lip asymmetrically lobate, anterior margin setose. Lower lip lost in dissection. Maxilla 1 palp 2-articulate with 3 distal setae; outer plate with 5 distal robust setae. Maxilla 2 inner plate with 3 rows of 2, 2, and 3 distal setae, with 3 proximal marginal setae; outer plate with 2 distal robust setae and 13 marginal setae. Maxilliped inner plates with wide v-shaped indentation distally, with short simple robust setae and long slender setae; outer plate inner margin smooth, reaching 0.5 × 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: 1.0: 0.8: 1.4. Gnathopod 1 coxa with tiny marginal setae, anterodistal margin produced, subquadrate, serrate, distal margin straight, posterior margin excavate, facial setae absent; basis distally expanded, anterior margin with 7 short and medium setae, posterior margin bare; ischium with 2 short posterior setae; carpus linear, distal length 10.4 × width, proximal margin dentate, distal margin with 4 setae; propodus straight, palm dentate with 5 distal setae; dactylus smooth, reaching 0.3 × propodus length. Gnathopod 2 coxa broader than long, slightly larger than coxa 3, smooth, with tiny marginal setae, anterior margin expanded, anterodistally rounded, distal and posterior margins rounded, facial setae absent; basis distally expanded, anterior margin with 5 short and medium setae, posterior margin with 2 short setae; ischium with anterodistal, distal, and posterodistal setae; carpus 0.4 × propodus length, curved, distally truncate, anterior margin dentate; propodus with 1 mediofacial setal row displaced past midline, reaching 0.7 × propodus length, with 1 row of submarginal setae, posterior margin smooth, palm convex with 3 major and many small tubercles; dactylus curved, proximal margin smooth, bare, anterior margin distally acute, reaching 0.4 × propodus length. Pereopod 3 coxa length 1.1 × width, anterodistal corner overriding distal face of coxa 2 and extending below it, smooth, with tiny marginal setae, anterior margin straight, distal margin oblique, posterior margin straight, facial setae absent. Pereopod 4 coxa smooth, with tiny marginal setae, anterior margin tapered, distal margin rounded, posterior margin excavate, facial setae absent. Pereopod 5-6 coxae facial setae present, pereopod 7 coxa facial setae absent. Pereopods 5-7 bases width length ratios 1: 1.2, 1: 1.2, 1: 1.2, posterior margins serrate, setose.

Pleon. Epimeron 1 with 1 antero-ventral seta, epimera 2-3 with ventral setae; epimeron 3 posteroventral corner subquadrate, produced. Uropods 1-3 relative lengths 1.0: 0.7: 1.0. Uropod 1 peduncle and outer ramus subequal in length with inner ramus; inner ramus with 3 robust setae, outer ramus with 4 robust setae. Uropod 2 peduncle 0.8 × inner ramus length, outer ramus 0.6 × inner ramus length; inner ramus with 4 robust setae, outer ramus with 3 robust setae. Uropod 3 peduncle and outer ramus 0.9 × inner ramus length; inner ramus with 3 robust setae, outer ramus with 1 robust seta. Telson 2.4 × longer than wide, apex weakly tridentate.

Male (sexually dimorphic characters).

Unknown.

Etymology.

After the Japanese words ‘chiisai’, meaning ‘small’ and ‘me’, meaning ‘eye’ and referring to the very small eye (pronounced chee-sy-nah-may).

Ecology.

Host unknown, presumably in sponges in coral rubble.

Relationships.

Leucothoe chiisainame sp. n. shares a rounded anteroventral head margin, truncate gnathopod 2 carpus, broadly expanded pereopod 5-7 bases, and a tuft of anteroventral setae on epimeron 1 with Leucothoe alcyone Imbach, 1967, Leucothoe occidentalis (Reid, 1951), Leucothoe saron Thomas & Klebba, 2007, and Leucothoe vulgaris White & Reimer, 2012a. Leucothoe chiisainame sp. n. differs from these species in the following: head anterior margin excavate, eye small; maxilla 2 with rows of apical setae; gnathopod 1 coxa anterodistally serrate; gnathopod 2 dactylus short; pereopods 5-7 bases posteriorly serrate; and epimeron 3 posteroventral corner produced.

Remarks.

Leucothoe chiisainame sp. n. is white in color with a very small yellow-orange eye (Figure 15F). This species is endemic to Yakushima Island. Although there is only one specimen available for analysis, the authors are confident that this is a new species based on the diagnostic characters.

Distribution.

East China Sea: Yakushima Island, Kagoshima, Japan.