Leucothoe akaoni, 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 : 3-5

Leucothoe akaoni sp. n. Figures 12

Type material.

Holotype female, 9.6 mm RUMF-ZC-1732, Zanpa Cape, Okinawa–jima Island, Okinawa, reef wall (26°26'27"N, 127°43'03"E), in canals of large white ball sponge, Tetillidae of Sollas 1886, 30 m, Daisuke Ueno, col., 26 February 2011 (KNWOkinawa34C). Paratype male, 8.3 mm, RUMF-ZC-1733, Zanpa Cape, Okinawa–jima Island, Okinawa, reef wall (26°26'27"N, 127°43'03"E), in canals of large white ball sponge, 30-33 m, K.N. White and N.S. White, col., 3 April 2011 (KNWOkinawa40D).

Type locality.

Zanpa Cape, Okinawa–jima Island, Okinawa, Japan (26°26'27"N, 127°43'03"E).

Additional material examined.

1 specimen, RUMF-ZC-1734, KNW17Aug10; 1 specimen, NSMT-Cr 21871, KNWOkinawa10A; 3 specimens, NSMT-Cr 21872, KNWOkinawa15G; 2 specimens, RUMF-ZC-1735, KNWOkinawa16I; 2 specimens, RUMF-ZC-1736, KNWOkinawa29D; 0.5 specimen, NSMT-Cr 21873, KNWOkinawa34C; 15 specimens, NSMT-Cr 21874, KNWYaku2F; 1 specimen, RUMF-ZC-1737, KNWOkinawa40D.

Diagnosis (female).

Ventral cephalic keel anteroventral margin with anteriorly projecting cusp. Right mandible lacinia mobilis with 2 rows of dentition. Maxilliped inner plates with short serrate robust setae. Gnathopod 1 coxa anterior margin serrate; basis anterior margin with 12 medium-length setae, posterior margin with 14 short setae. Gnathopod 2 basis anterior margin with 33 medium-length setae, posterior margin with 7 setae, distal margin with 4 curved setae; ischium with several short posterior and distal setae and posterodistal serrations; carpus distally truncate.

Description (female).

Head. Anterior margin rounded, anterodistal margin evenly rounded; ventral cephalic keel anterior margin excavate, anteroventral margin with anteriorly projecting cusp, ventral margin straight; eyes present with more than 10 ommatidia, oval. Antenna 1 0.3 × body length, flagellum 10-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 8-articulate. Mandibular palp ratio of articles 1-3 1.0: 2.6: 1.7, article 2 with 8-9 long distal setae, article 3 with 2 distal setae, incisors strongly dentate; left mandible with 16 raker spines, lacinia mobilis large, strongly toothed; right mandible with 14 raker spines, lacinia mobilis small, with 2 rows of dentition. Upper lip asymmetrically lobate, anterior margin setose. Lower lip inner lobes fused, bare; outer lobes with small gape, anterior margins setose. Maxilla 1 palp 2-articulate with 4 distal setae; outer plate with 9 distal robust setae and 4 distal slender setae. Maxilla 2 inner plate with 8 slender distal setae, 6 robust marginal setae, and facial setae; outer plate with 2 robust and 6 slender distal setae, 9 slender marginal setae, and facial setae. Maxilliped inner plates distal margin with a v-shaped indentation, with short serrate robust setae; outer plate inner margin smooth, reaching 0.3 × 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: 1.3: 1.0: 1.4. Gnathopod 1 coxa with tiny marginal setae, anterior margin serrate, anterodistal margin produced, rounded, distal margin straight, posterior margin excavate, facial setae absent; basis slightly inflated, anterior margin with 12 short setae, posterior margin with 14 short setae; ischium with posterior setae; carpus linear, distal length 12.9 × width, proximal margin dentate, distal margin with 3 setae; propodus straight, palm dentate with 8 distal setae; dactylus smooth, reaching 0.5 × 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 margin straight, posterior margin straight, facial setae absent; basis slightly posteriorly expanded, anterior margin with 33 medium setae, posterior margin with 7 setae, distal margin with 4 curved setae; ischium with several short posterior and distal setae and posterodistal serrations; carpus 0.3 × propodus length, curved, distally truncate, anterior margin dentate; propodus with 1 mediofacial setal row displaced to midline, reaching 0.8 × propodus length, with 1 row of submarginal setae, posterior margin smooth, palm convex dentate; dactylus curved, proximal margin smooth, bare, anterior margin distally subacute, reaching 0.6 × propodus length. Pereopod 3 coxa length 1.3 × width, anterodistal corner overriding distal face of coxa 2 and extending below it, smooth, bare, anterior margin straight, distal margin oblique, posterior margin tapered, facial setae absent. Pereopod 4 coxa smooth, bare, anterior margin straight, distal margin evenly rounded, posterior margin tapered, facial setae absent. Pereopods 5-7 coxae facial setae absent; bases width length ratios 1: 1.4, 1: 1.4, 1: 1.3, posterior margins smooth, setose.

Pleon. Epimera 1 and 3 bare, epimeron 2 with ventral setae; epimeron 3 posteroventral corner subquadrate. Uropods 1-3 relative lengths 1.0: 0.8: 1.1. Uropod 1 peduncle and outer ramus 0.9 × inner ramus length; inner ramus with 3 robust setae; outer ramus with 7 robust setae. Uropod 2 peduncle length 0.7 × inner ramus length, outer ramus length 0.6 × inner ramus length; inner ramus with 4 robust setae; outer ramus with 7 robust setae. Uropod 3 peduncle 1.3 × inner ramus length, outer ramus length subequal in length with inner ramus; inner ramus with 4 robust setae; outer ramus with 5 robust setae. Telson 2.7 × longer than wide, apex strongly tridentate.

Male (sexually dimorphic characters).

Gnathopod 1 basis anterior margin with 7 setae, posterior margin with 5 setae. Gnathopod 2 basis anterior margin with 9 long setae, posterior margin bare; ischium with posterodistal setae, smooth.

Etymology.

After the Japanese words ‘aka’, meaning ‘red’, and ‘oni’, meaning ‘barbarian’ and referring to the red color and large size (pronounced ah-ka-oh-nee).

Ecology.

In canals of sponges, spiculose green ball sponge,? Axinyssa of Lendenfeld 1897 (Figure 24E); spiculose beige sponge, Niphatidae of Van Soest 1980 (probably Niphates of Duchassaing and Michelotti 1864), RUMF-ZP-6, KNWOkinawa10A (Figure 25I); large white ball sponge, Tetillidae , RUMF-ZP-11, KNWOkinawa40E (Figure 24I); and among coral rubble.

Relationships.

Leucothoe akaoni sp. n. is similar to Leucothoe denticulata Costa, 1851 and Leucothoe wuriti Thomas & Klebba, 2007 in having a rounded head, ventral cephalic keel with projection, gnathopod 1 dactylus reaching greater than 0.2 × propodus length, and a truncate gnathopod 2 carpus. Leucothoe akaoni sp. n. differs from these species in lacking facial setae on coxa 1, having a setose posterior margin on the gnathopod 1 basis, gnathopod 2 basis anterior margin with more than 9 setae, slightly less broadly expanded bases on pereopods 5-7.

Remarks.

Leucothoe akaoni sp. n. is deep red in color, darkest on the head, fading to deep orange posteriorly (Figure 23A). This species has been collected only on Yakushima Island, Kagoshima and from the northwestern coast of Okinawa–jima Island, Okinawa.

Distribution.

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