Leucothoe togatta, 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 : 26-30

Leucothoe togatta sp. n. Figures 1718

Type material.

Holotype male, 4.2 mm RUMF-ZC-1778, Yoshida, Yakushima Island, Kagoshima, patch reef (30°23'58"N, 130°25'53"E), among coral rubble, 3-7 m, K.N. White and N.S. White, col., 26 May 2011 (KNWYaku2E). Paratype female, 5.4 mm RUMF-ZC-1779, same station data as holotype.

Type locality.

Yoshida, Yakushima Island, Kagoshima, Japan (30°23'58"N, 130°25'53"E).

Additional material examined.

2 specimens, RUMF-ZC-1780, KNWYaku5M; 1 specimen, NSMT-Cr 21900, KNWOkinawa35A; 1 specimen, RUMF-ZC-1781, KNWOkinawa36E; 1 specimen, RUMF-ZC-1782, KNWYaku1F; 1 specimen, NSMT-Cr 21901, KNWOkinawa51D; 1 specimen, RUMF-ZC-1783, KNWYaku1G; 1 specimen, KNWOkinawa55E.

Diagnosis (male).

Ventral cephalic keel anteroventral margin quadrate with large projection. Antenna 1 accessory flagellum 1-articulate. Mandibular palp article 2 with 11 long distal setae; article 2 with facial setae and 1 distal seta. Gnathopod 2 basis anterior margin with 7 long curved setae; carpus with setulate-serrate marginal setae; propodus with 3 mediofacial setal rows. Pereopod 7 basis posterior margin serrate. Female gnathopod 1 carpus elongate; gnathopod 2 basis anterior margin with 22 long curved setae, distal margin with 4 long curved setae; ischium with 3 long and 2 short distal setae, carpus distally truncate.

Description (male).

Head. Anterior margin rounded, anterodistal margin evenly rounded; ventral cephalic keel anterior margin excavate, anteroventral margin quadrate with projection, ventral margin convex; eyes 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 8-articulate. Mandibular palp ratio of articles 1-3 1.0: 3.4: 2.0, article 2 with 11 long distal setae, article 3 with facial setae and 1 distal seta, incisors strongly dentate; left mandible with 10 raker spines, lacinia mobilis large, strongly toothed; right mandible with 11 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 2-articulate with 4 distal setae; outer plate with 9 distal robust setae. Maxilla 2 inner plate with 5 robust distal setae, 1 robust facial seta, and several slender facial setae; outer plate with 3 robust distal setae and 13 slender distal marginal setae. Maxilliped inner plates distal margin with a v-shaped indentation, with short robust setae; outer plate inner margin smooth, reaching 0.1 × 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: 1.2: 0.9: 1.6. Gnathopod 1 coxa smooth, bare, anterodistal margin produced, subquadrate, distal margin straight, posterior margin excavate, facial setae absent; basis distally expanded, anterior margin with 5 medium setae, posterior margin bare; ischium bare; carpus linear, distal length 11.2 × width, proximal margin smooth, distal margin with 2 short setae; propodus straight, palm dentate with 7 robust and 12 distal setae; dactylus smooth, reaching 0.4 × propodus length. Gnathopod 2 coxa broader than long, subequal in size with coxae 3, smooth, bare, anterior margin straight, anterodistally rounded, distal and posterior margins straight, facial setae absent; basis slightly posteriorly expanded, anterior margin with 7 long curved setae, distal margin with 2 long setae, posterior margin bare; ischium with 2 distal setae; carpus 0.3 × propodus length, curved, distally tapered, anterior margin smooth, with setulate-serrate marginal setae; propodus with 1 mediofacial setal row above midline, reaching 0.8 × propodus length, with 3 rows of submarginal setae, posterior margin smooth, palm convex with 2 large and several small tubercles; dactylus curved, proximal margin smooth with 2 setae, anterior margin distally acute, 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 straight, facial setae absent. Pereopod 4 coxa smooth, bare, anterior margin produced, distal margin evenly rounded, posterior margin excavate, facial setae absent. Pereopods 5-7 coxae facial setae absent, bases width length ratios 1: 1.3, 1: 1.2, 1: 1.2, posterior margins bare; pereopods 5-6 bases posterior margins smooth, pereopod 7 basis posterior margin serrate.

Pleon. Epimera 1-2 with ventral setae, epimeron 3 bare; epimeron 3 posteroventral corner subquadrate. Uropods 1-2 relative lengths 1.0: 0.9. Uropod 1 peduncle 0.7 × inner ramus length, outer ramus 0.8 × inner ramus length; inner ramus with 4 robust setae on each margin; 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 missing. Telson 2.3 × longer than wide, with 2 simple facial setae, apex weakly tridentate.

Female (sexually dimorphic characters).

Gnathopod 1 carpus length 10.8 × width; basis anterior margin with 8 long setae. Gnathopod 2 basis distally expanded, anterior margin with 22 long curved setae, distal margin with 4 long curved setae; ischium with 3 long and 2 short distal setae; carpus distally truncate, anterior margin dentate; propodus palm with 1 row of submarginal setae.

Etymology.

After the Japanese word ‘togatta’, meaning ‘sharp’ and referring to the sharply pointed projection on the ventral cephalic keel. (Pronounced toe-ga-ta)

Ecology.

In canals of hard brown sponge, yellow inside with groups of small holes on top,? Jaspis of Gray, 1867 (Figure 25C); and among coral rubble.

Relationships.

Leucothoe togatta sp. n. is similar to Leucothoe ashleyae Thomas & Klebba, 2006 and Leucothoe saron Thomas & Klebba, 2007 in having a rounded head margin, a 2-articulate maxilla 1 palp, high mediofacial setal row on gnathopod 2 propodus, wide pereopod 5-7 bases, and a tridentate telson. It also shares long curved setae on the distal margin of gnathopod 2 basis with Leucothoe saron . It differs from these species in having a ventral cephalic keel that is anteriorly excavate and anteroventrally quadrate with a projection. Leucothoe togatta sp. n. shares these keel characteristics with Leucothoe amamiensis White & Reimer, 2012a and Leucothoe hashi sp. n., but differs from Leucothoe amamiensis in the distally truncate gnathopod 2 carpus, from Leucothoe hashi in the robustness of gnathopod 1 propodus and length of gnathopod 1 dactylus, and from both species in the long curved setae on gnathopod 2 basis and robust row of submarginal setae on the gnathopod 2 propodus.

Remarks.

Leucothoe togatta sp. n. is white in color (Figure 23G). This species has been collected only on Yakushima Island and from both western and eastern coasts of Okinawa–jima Island, Okinawa.

Distribution.

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