Leucothoe akuma, 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 : 21-24

Leucothoe akuma sp. n. Figures 5 6

Type material.

Holotype male, 2.9 mm RUMF-ZC-1861, Toguchi Beach, Okinawa–jima Island, Okinawa, patch reef (26°21'47"N, 127°44'12"E), among coral rubble, 1-2 m, K.N. White and N.S. White, col., 20 October 2010 (KNWOkinawa14I). Paratype female, 2.5 mm, RUMF-ZC-1862, Toguchi Beach, Okinawa–jima Island, Okinawa, patch reef (26°21'47"N, 127°44'12"E), among coral rubble, 1-2 m, K.N. White and N.S. White, col., 9 September 2011 (KNWOkinawa63A).

Type locality.

Toguchi Beach, Okinawa–jima Island, Okinawa, Japan (26°21'47"N, 127°44'12"E).

Additional material examined.

1 specimen, RUMF-ZC-1863, KNWOkinawa39N; 1 specimen, RUMF-ZC-1864, KNWOkinawa41D; 2 specimens, NSMT-Cr 22000, KNWOkinawa63A; 2 specimens, NSMT-Cr 22001, KNWOkinawa72A.

Diagnosis (male).

Head anterior margin rounded; ventral cephalic keel anterior margin excavate, anteroventral margin quadrate, projected anteriorly. Antenna 1 accessory flagellum 1-articulate. Gnathopod 1 dactylus reaching 0.3 × propodus length. Gnathopod 2 carpus distally truncate; propodus with 2 mediofacial setal rows, secondary row reaching to insertion of dactylus. Pereopods 5-6 coxae with facial setae; bases broadly expanded.

Description (male).

Head. Anterior margin rounded, anterodistal margin evenly rounded, distal margin rounded; ventral cephalic keel anterior margin excavate, anteroventral margin quadrate, projected anteriorly, ventral margin convex; eyes present with more than 10 ommatidia, round. Antenna 1 0.3 × body length, flagellum 10-articulate, peduncle article 1 width less than 2 × article 2, accessory flagellum 1-articulate. Antenna 2 0.3 × body length, subequal in length with antenna 1, flagellum 7-articulate. Mandibular palp ratio of articles 1-3 1.0: 2.6: 1.8, article 2 with 8 distal setae, article 3 with one distal seta; incisors strongly dentate; left mandible with 7 raker spines, lacinia mobilis large, weakly toothed; right mandible with 7 raker spines, lacinia mobilis small, weakly toothed. Upper lip asymmetrically lobate, anterior margin setose. Lower lip inner lobes fused, setose; outer lobes with small gape, anterior margins setose. Maxilla 1 palp 2-articulate with 3 distal setae; outer plate with 5 distal robust setae. Maxilla 2 inner plate with 7 distal setae; outer plate with 7 slender distal setae, 4 slender and 4 robust marginal setae. Maxilliped inner plates distal margin with v-shaped indentation, with short simple robust setae; outer plate inner margin smooth, reaching 0.3 × palp article 1, with simple marginal setae, facial setae absent; palp article 4 subequal in length with article 3, distally acute.

Pereon. Coxae 1-4 relative widths 1.0: 1.1: 0.7: 1.3. Gnathopod 1 coxa smooth, with tiny marginal setae, anterodistal margin produced, subquadrate, distal margin straight, posterior margin excavate, facial setae absent; basis distally expanded, anterior margin with 3 short setae, posterior margin bare; ischium bare; carpus linear, distal length 12.9 × width, proximal margin smooth, distal margin with 3 setae; propodus straight, palm dentate with 5 large and several small distal setae; dactylus smooth, reaching 0.3 × propodus length. Gnathopod 2 coxa broader than long, subequal in size with coxa 3, smooth, with tiny marginal setae, anterior margin straight, anterodistally rounded, distal and posterior margins straight, facial setae absent; basis distally expanded, anterior margin with 7 short and long setae, posterior margin bare except for 1 small posterodistal seta; ischium with distal and posterodistal setae; carpus 0.4 × propodus length, curved, distally truncate, anterior margin dentate; propodus with 2 mediofacial setal rows, primary row above midline, reaching 0.7 × propodus length, secondary row reaching to insertion of dactylus, with 1 row of submarginal setae, posterior margin smooth, palm convex with 2 large distal tubercles; dactylus curved, proximal margin smooth, setose, 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 convex, posterior margin straight, facial setae absent. Pereopod 4 smooth, with tiny marginal setae, anterior margin straight, distal margin rounded, posterior margin tapered, facial setae absent. Pereopods 5-7 coxae facial setae present; bases width length ratios 1: 1.3, 1: 1.2, 1: 1.1, posterior margins smooth. Pereopod 5 basis posterior margin bare, pereopods 6-7 bases posterior margins setose.

Pleon. Epimera 1-3 with ventral setae; epimeron 3 posteroventral corner rounded. Uropods 1-3 relative lengths 1.0: 0.7: 1.0. Uropod 1 peduncle 0.9 × inner ramus length, outer ramus length 0.8 × inner ramus length; inner ramus with 5 robust setae, outer ramus with 4 robust setae. Uropod 2 peduncle 0.8 × inner ramus length, outer ramus 0.7 × inner ramus length; inner ramus with 4 robust setae, outer ramus with 3 robust setae. Uropod 3 peduncle and outer ramus subequal in length with inner ramus; inner ramus with 5 robust setae, outer ramus with 3 robust setae. Telson 2.4 × longer than wide, apex tridentate.

Female (sexually dimorphic characters).

Gnathopod 1 carpus posterodistal margin with 2 setae; propodus palm with 6 large and several small distal setae. Gnathopod 2 basis anterior margin with 10 long setae, distal margin with 2 long setae.

Etymology.

After the Japanese word ‘akuma’, meaning ‘devil’ and referring to the type locality, also known as ‘Devil’s Cove’ (pronounced ah-koo-ma).

Ecology.

Host unknown, presumably in sponges in coral rubble.

Relationships.

Leucothoe akuma sp. n. is similar to Leucothoe togatta White & Reimer, 2012b, Leucothoe hashi White & Reimer, 2012b, and Leucothoe amamiensis White & Reimer, 2012a in having a rounded anterodistal head margin and a ventral cephalic keel with an excavate anterior margin and a produced, quadrate anteroventral margin. Leucothoe akuma sp. n. differs from Leucothoe hashi in the overall shape of gnathopod 1 and from the other species in having mandibular palp article 2 with fewer distal setae, lower lip with setose inner lobes, gnathopod 2 carpus longer and distally truncate, and gnathopod 2 propodus medial surface with two rows of submarginal setae. This last unique character is shared only with Leucothoe enko sp.n.

Remarks.

Leucothoe akuma sp. n. is white in color with magenta-pink stripes along pereonite edges (Figure 15H). This species is endemic to the central Ryukyu Islands.

Distribution.

East China Sea: Okinawa–jima Island (Okinawa) and Okinoerabu–jima Island (Kagoshima), Japan.