Leucothoe hashi, 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 : 11-14

Leucothoe hashi sp. n. Figures 78

Type material.

Holotype male, 2.5 mm RUMF-ZC-1747, Mizugama, Okinawa–jima Island, Okinawa, reef wall (26°21'35"N, 127°44'22"E), in canals of yellow-beige sponge, Callyspongia of Duchassaing and Michelotti 1864, 8-10 m, K.N. White, col., 10 April 2011 (KNWOkinawa42A). Paratype female, 2.5 mm RUMF-ZC-1748, same station data as holotype. Paratype male, 1.9 mm RUMF-ZC-1749, Kaichu Doro, Okinawa–jima Island, Okinawa, seagrass bed (26°19'56"N, 127°55'23"E), in canals of green, hard branching sponge,? Clathria (Thalysias) reinwardti Vosmaer, 1880, 1 m, K.N. White, col., 21 August 2010 (KNW_21Aug10).

Type locality.

Mizugama, Okinawa–jima Island, Okinawa, Japan (26°21'35"N, 127°44'22"E).

Additional material examined.

1 specimen, RUMF-ZC-1750, KNW21Aug10; 2 specimens, RUMF-ZC-1751, KNWOkinawa11B; 1 specimen, RUMF-ZC-1752, KNWOkinawa12H; 1 specimen, NSMT-Cr 21882, KNWOkinawa12H; 1 specimen, RUMF-ZC-1753, KNWOkinawa16D; 1 specimen, RUMF-ZC-1754, KNWOkinawa21B; 1 specimen, NSMT-Cr 21883, KNWOkinawa21E; 1 specimen, RUMF-ZC-1755, KNWOkinawa22B; 1 specimen, NSMT-Cr 21884, KNWOkinawa25C; 1 specimen, NSMT-Cr 21885, KNWOkinawa29C; 2 specimens, NSMT-Cr 21886, KNWOkinawa31B; 4 specimens, RUMF-ZC-1756, KNWOkinawa31F; 3 specimens, RUMF-ZC-1757, KNWOkinawa33E; 1 specimen, NSMT-Cr 21887, KNWOkinawa33E; 3 specimens, NSMT-Cr 21888, KNWOkinawa34G; 4 specimens, RUMF-ZC-1758, KNWOkinawa42A; 2 specimens, NSMT-Cr 21889, KNWOkinawa43A; 3 specimens, NSMT-Cr 21890, KNWOkinawa44A; 2 specimens, RUMF-ZC-1759, KNWIriomote2H; 1 specimen, NSMT-Cr 21891, KNWOkinawa51C; 1 specimen, RUMF-ZC-1760, KNWOkinawa53A; 2 specimens, NSMT-Cr 21892, KNWOkinawa53D; 1 specimen, RUMF-ZC-1761, KNWYaku5O; 2 specimens, RUMF-ZC-1762, KNWTokuno4C; 2 specimens, RUMF-ZC-1796, KNWYaku3J; 1 specimen, RUMF-ZC-1797, KNWYaku5I; 2 specimens, RUMF-ZC-1798, KNWOkinawa43D.

Diagnosis (male).

Antenna 1 accessory flagellum 1-articulate. Mandibular palp article 3 shorter than article 1. Maxilla 1 palp 1-articulate. Maxilliped outer plate tuberculate. Gnathopod 1 carpus and propodus very slender, chopstick-like; carpus proximal margin with denticles; propodus palm serrate with triangular teeth. Gnathopod 2 propodus with 2 mediofacial setal rows. Pereopods 5-7 bases narrowly expanded.

Description (male).

Head. Anterior margin rounded, anterodistal margin evenly rounded; ventral cephalic keel anterior margin slightly excavate, anteroventral margin subquadrate, ventral margin straight; eyes with more than 10 ommatidia, round. Antenna 1 0.3 × body length, flagellum 5-articulate, peduncle article 1 width less than 2 × article 2, accessory flagellum 1-articulate. Antenna 2 0.2 × body length, slightly shorter than antenna 1, flagellum 5-articulate. Mandibular palp ratio of articles 1-3 1.0: 2.0: 0.4, article 2 with 2 medium distal setae, article 3 with 1 distal seta, incisors weakly dentate; left mandible with 6 raker spines, lacinia mobilis large, strongly toothed; right mandible with 6 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 1-articulate with 4 distal setae; outer plate with 5 distal robust setae. Maxilla 2 inner plate with 5 robust distal setae and 2 robust facial setae; outer plate with 3 robust distal setae and 4 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 absent; palp article 4 subequal in length with article 3, distally acute.

Pereon. Coxae 1-4 relative widths 1.0: 1.2: 1.2: 1.3. Gnathopod 1 coxa smooth, with tiny marginal setae, anterodistal margin produced, rounded, distal margin straight, posterior margin slightly excavate, facial setae absent; basis distally expanded, anterior margin bare, posterior margin with 2 short setae; ischium bare; carpus linear, distal length 15.8 × width, proximal margin with denticles, distal margin bare; propodus straight, palm serrate with 7 distal triangular teeth and 7 distal setae; dactylus with small proximal notch, reaching 0.2 × propodus length. Gnathopod 2 coxa as long as broad, subequal in size with coxa 3, smooth, with tiny marginal setae, anterior margin expanded, anterodistally rounded, distal and posterior margins straight, facial setae absent; basis distally expanded, anterior margin with 5 medium setae, posterior margin with 1 seta; ischium with 1 posterodistal seta; carpus 0.3 × 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 with 4 small denticles; dactylus curved, proximal margin smooth with 1 seta, anterior margin distally subacute, reaching 0.8 × propodus length. Pereopod 3 coxa length 1.0 × 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 straight, distal margin evenly rounded, posterior margin tapered, facial setae absent. Pereopods 5-7 coxae facial setae absent; bases width length ratios 1: 1.5, 1: 1.5, 1: 1.7, 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: 1.2; inner and outer rami lined with short marginal setae. Uropod 1 peduncle and outer ramus 0.8 × inner ramus length; inner ramus with 6 robust setae and outer ramus with 5 robust setae. Uropod 2 peduncle 0.7 × inner ramus length, outer ramus 0.6 × inner ramus length; inner ramus with 3 robust setae and outer ramus with 4 robust setae. Uropod 3 peduncle 1.2 × inner ramus length, outer ramus 0.9 × inner ramus length; inner ramus with 4 robust setae and outer ramus with 7 robust setae. Telson 2.0 × longer than wide, apex weakly tridentate, almost bidentate.

Female (sexually dimorphic characters).

Gnathopod 1 basis posterior margin with 5 short setae. Gnathopod 2 basis posterior margin with 4 medium setae; ischium with 2 posterior and1 posterodistal seta; carpus distally tapered; propodus secondary mediofacial setal row with 4 setae.

Etymology.

After the Japanese word ‘hashi’, meaning ‘chopsticks’ and referring to the extremely slender carpus and propodus of gnathopod 1. (Pronounced hah-shee.)

Ecology. In canals of sponges, Callyspongia sp., RUMF-ZP-2, KNWOkinawa42C (Figure 24F),? Clathria (Thalysias) reinwardti , RUMF-ZP-4, 21Aug10 (Figure 25F), Tedania sp. (Figure 25E), Haliclona of Grant 1836, RUMF-ZP-3, KNWOkinawa44A (Figure 24G); and among coral rubble.

Relationships.

Leucothoe hashi sp. n. is similar to Leucothoe cheiriserra Serejo, 1998, Leucothoe gavialis Myers, 1985, Leucothoe hipposideros White & Thomas, 2009, Leucothoe squalidens Ledoyer, 1984, and Leucothoe lecroyae sp. n. in having triangular teeth on the palm of gnathopod 1 propodus. It also shares a rounded anterodistal head margin and distally truncate gnathopod 2 carpus with Leucothoe hipposideros and Leucothoe squalidens , but differs in having narrow pereopod 5-7 bases, a 1-articulate maxilla 1 palp, tuberculate maxilliped inner plate, and a 1-articulate accessory flagellum on antenna 1.

Remarks.

Leucothoe hashi sp. n. is translucent pink in color, darkest along pereonite edges (Figure 24A). This species has been collected from only 5 islands throughout the Ryukyu Archipelago. There appears to be some minor variation among specimens in the following characters: gnathopod 1 carpus dentition, propodus palm serration; gnathopod 2 shape and setal patterns.

Distribution.

East China Sea: Iriomote–jima Island, Okinawa–jima Island (both Okinawa), Tokunoshima Island, Amami–oshima Island, Yakushima Island (all Kagoshima), Japan.