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

White, Kristine N. & Reimer, James Davis, 2012, Commensal Leucothoidae (Crustacea, Amphipoda) of the Ryukyu Archipelago, Japan. Part II: sponge-dwellers, ZooKeys 166, pp. 1-58 : 22-26

Leucothoe ouraensis sp. n. Figures 1516

Type material.

Holotype male, 3.3 mm RUMF-ZC-1774, Kita–nakase, Oura–wan Bay, Okinawa–jima Island, Okinawa, patch reef (26°32'40"N, 128°03'36"E), among coral rubble, 30 m, K.N. White and N.S. White, col., 3 March 2011 (KNWOkinawa35F). Paratype female, 3.0 mm RUMF-ZC-1775, Tettou–mae–oki, Oura–wan Bay, Okinawa–jima Island, Okinawa, patch reef (26°32'43"N, 128°02'56"E), among coral rubble, 28 m, K.N. White, col., 4 April 2011 (KNWOkinawa37G).

Type locality.

Oura–wan Bay, Okinawa–jima Island, Okinawa, Japan (26°32'40-43"N, 128°02'56"-03'36"E).

Additional material examined.

1 specimen, RUMF-ZC-1776, KNWOkinawa39H; 1 specimen, NSMT-Cr 21898, KNWOkinawa39L; 1 specimen, RUMF-ZC-1777, KNWOkinawa37C; 2 specimens, NSMT-Cr 21899, KNWOkinawa37N.

Diagnosis (male).

Head anterior margin truncate, anterodistal margin quadrate. Ventral cephalic keel anteroventral margin with anteriorly projecting cusp. Right mandible lacinia mobilis cleft. Upper lip distal margin with row of short setae. Maxilla 1 palp 1-articulate, proximal margin serrate. Maxilliped outer plate tuberculate. Gnathopod 1 basis posterior margin with 6 short setae; propodus palm serrate; dactylus reaching 0.1 × propodus length. Gnathopod 2 carpus distally truncate; propodus with 2 mediofacial setal rows. Uropod 3 peduncle 1.2 × inner ramus length. Telson apex bidentate.

Description (male).

Head. Anterior margin truncate, anterodistal margin quadrate; ventral cephalic keel anterior margin oblique, anteroventral margin with anteriorly projecting cusp, ventral margin convex; eyes with more than 10 ommatidia, round. Antenna 1 0.3 × body length, flagellum 8-articulate, peduncle article 1 width less than 2 × article 2, accessory flagellum absent. Antenna 2 0.3 × body length, subequal in length with antenna 1, flagellum 5-articulate. Mandibular palp ratio of articles 1-3 1.0: 2.4: 1.6, article 2 with 3 medium distal setae, article 3 with 2 distal setae, incisors weakly dentate; left mandible with 9 raker spines, lacinia mobilis large, strongly toothed; right mandible with 7 raker spines, lacinia mobilis small, strongly dentate, cleft. Upper lip asymmetrically lobate, anterior margin setose, distal margin with row of short setae. Lower lip inner lobes fused, setose; outer lobes with moderate gape, anterior margins setose. Maxilla 1 palp 1-articulate with 4 distal setae, proximal margin serrate; outer plate with 4 distal robust setae and 4 distal setae. Maxilla 2 inner plate with 3 robust distal setae and 4 slender marginal setae; outer plate with 2 robust and 2 slender distal setae and 6 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 × 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: 1.2: 0.9: 1.7. Gnathopod 1 coxa smooth, with tiny marginal setae, anterior margin produced, rounded, distal margin straight, posterior margin excavate, facial setae absent; basis distally expanded, anterior margin bare, posterior margin with 6 short setae; ischium bare; carpus linear, distal length 13.6 × width, proximal margin smooth, distal margin bare; propodus straight, palm serrate with 9 distal setae; dactylus smooth, reaching 0.1 × propodus length. Gnathopod 2 coxa as long as broad, subequal in size with coxa 3, smooth, with tiny marginal setae, anterior margin straight, anterodistally rounded, distal margin evenly rounded, posterior margin straight, facial setae absent; basis distally expanded, anterior margin with 9 setae, posterior margin with 4 setae; ischium with 1 posterodistal seta; carpus 0.4 × propodus length, curved, distally truncate, anterior margin dentate; propodus with 2 mediofacial setal rows, primary mediofacial setal row above midline, reaching 0.8 × propodus length, secondary mediofacial setal row with 2 setae, with 1 row of submarginal setae, posterior margin smooth, palm convex, dentate; dactylus curved, proximal margin smooth with 1 seta, anterior margin distally acute, reaching 0.6 × propodus length. Pereopod 3 coxa length 1.4 × width, anterodistal corner overriding distal face of coxa 2 and extending below it, smooth, with tiny marginal setae, anterior margin straight, distal margin slightly convex, 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. Pereopods 5-7 bases width length ratios 1: 1.4, 1: 1.2, 1: 1.1; posterior margins smooth, setose.

Pleon. Epimera 1-2 with ventral setae, epimeron 3 bare; epimeron 3 posteroventral corner rounded. Uropods 1-3 relative lengths 1.0: 0.8: 1.1; outer rami lined with short marginal setae. Uropod 1 peduncle and outer ramus subequal in length with inner ramus; inner ramus with 2 robust setae; outer ramus without robust setae. Uropod 2 peduncle length 0.8 × inner ramus, outer ramus length 0.6 × inner ramus; inner ramus with 4 robust setae; outer ramus with 3 robust setae. Uropod 3 peduncle length 1.2 × inner ramus, outer ramus subequal in length with inner ramus; inner and outer rami lined with short marginal setae, each with 4 robust setae. Telson 2.7 × longer than wide, apex bidentate.

Female (sexually dimorphic characters).

Gnathopod 2 ischium with posterior and posterodistal setae; carpus distally tapered, anterior margin smooth; propodus secondary mediofacial setal row with 4 setae.

Etymology.

After the Japanese place name ‘Oura’, meaning 'large inlet’ and referring to the type locality. (Pronounced oh-ooh-ra)

Ecology. In canals of brown-red chimney sponge, Mycale of Gray 1867, RUMF-ZP-8, KNWOkinawa37K (Figure 25B), brown-red holey sponge, Mycale (Zygomycale) parishii (Bowerbank, 1875), RUMF-ZP-9, KNWOkinawa37N (Figure 25G), brown bivalve encrusting sponge,? Mycale of Gray, 1867, RUMF-ZP-10, KNWOkinawa37M (Figure 25H); and among coral rubble.

Relationships.

Leucothoe ouraensis sp. n. is similar to Leucothoe ctenochasma Moore, 1987 in having gnathopod 1 dactylus reaching less than 0.1 × propodus length and a bidentate apex on the telson. This species differs from Leucothoe ctenochasma in having a truncate anterior head margin, quadrate anterodistal head margin, 1-articulate maxilla 1 palp, setose posterior margin on gnathopod 1 basis, and pereopods 5-7 bases broadly expanded and posteriorly smooth.

Remarks.

Leucothoe ouraensis sp. n. is yellow-orange in color (Figure 23E). This species is endemic to the eastern coast of Okinawa–jima Island, Okinawa.

Distribution.

East China Sea: Okinawa–jima Island, Okinawa, Japan.