Leucothoe cracentis, White & Machida, 2018

White, Kristine N. & Machida, Ryuji J., 2018, Taiwanese Leucothoidae (Crustacea: Amphipoda), Including Three New Species from Dongsha Atoll., Zoological Studies 57 (47), pp. 1-22 : 12-15

Leucothoe cracentis sp. nov.

( Figs. 3G , 6-7 )

urn:lsid:zoobank.org:act:457D5DF7-464A-46B1-BEE0-315C9AA6930A

Material Examined: Holotype: male, 1.8 mm, NMMB-CD 5585 , KNW-Dongsha-2017-4b, Dongsha Atoll southeast fore reef, 20°38'11.4"N, 116°54'25.85"E, 17 m; 22 May 2017; K.N. White, collector . Paratype: female, 2.2 mm, NMMB-CD 5586, same station data as Holotype.

Other: 1 male, 2 females, ASIZCR000422, same station data as Holotype. 2 males, 3 females, same station data as Holotype.

Etymology: Derived from the Latin ‘ cracens ’ meaning ‘slender, graceful, neat’ and referring to the overall appearance of gnathopod 1.

Diagnosis: Head anterior margin oblique, produced, distal margin straight. Eyes round. Accessory flagellum present, 1-articulate. Mandibular palp article 3 short, 0.9 × length of article 1. Gnathopod 1 carpus stout, anterior margin dentate; propodus slightly inflated, palm smooth; dactylus reaching 0.1 × propodus length. Gnathopod 2 carpus distally truncate, serrate. Pereopods 5-6 bases anterior and posterior margins nearly parallel, pereopod 7 basis posteriorly moderately produced.

Description (male holotype): Head: Anterior margin oblique, produced, distal margin straight; ventral cephalic keel anterior margin excavate, anteroventral margin rounded, ventral margin straight; eyes with more than 20 ommatidia, round.

Antenna 1 0.5 × body length, flagellum 7-articulate, peduncle article 1 width subequal to article 2, accessory flagellum present, 1-articulate. Antenna 2 0.4 × body length, shorter in length than antenna 1, flagellum 5-articulate.

Mandibular palp ratio of articles 1-3 1.0:2.3:0.9, article 2 with 2 marginal setae, article 3 with 2 distal setae, incisors nearly smooth; left mandible with 12 raker spines, lacinia mobilis large, strongly toothed; right mandible broken. Maxilla 1 palp 2-articulate, with 3 distal slender setae; outer plate with 2 distal robust spines, 4 distal robust setae and 3 slender setae. Maxilla 2 inner plate with 2 marginal and 4 distal slender setae, outer plate with 3 distal slender setae. Lower lip inner lobes with moderate gape ( Fig. 7B ). Maxilliped inner plates distal margin rounded, v-shaped, with short simple robust setae; outer plate inner margin smooth, not extended up toward palp article 1; palp article 4 subequal in length with article 3, distally narrowing and acute.

Pereon: Coxae 1-4 relative widths 1.0: 1.1: 1.1: 1.4. Gnathopod 1 coxa anterodistal margin produced, rounded, distal margin rounded with posterior notch, posterior margin convex; basis slightly distally expanded, anterior margin bare, posterior margin with 2 short setae; ischium bare; carpus distally curved, distal length 9 × width, anterior margin dentate with small short setae; propodus slightly inflated, palm smooth with short setae; dactylus smooth, reaching 0.1 × propodus length.

Gnathopod 2 coxa subquadrate, subequal in width with coxa 3, smooth, margins slightly rounded; basis not expanded, stout, anterior margin with 2 short setae, posterior margin bare; ischium bare; carpus 0.4 × propodus length, curved, setose, distally truncate, serrate; propodus with one high mediofacial setal row reaching 0.7 × propodus length, submarginal setal row with 4 setae, anterior margin gently curved, smooth, palm with 2 large and many small tubercles; posterior margin straight; dactylus curved, proximal margin smooth, bare, anterior margin distally subacute, reaching 0.6 × propodus length.

Pereopod 3 coxa anterior margin straight, distal margin slightly rounded with anterior and posterior notches, posterior margin straight. Pereopod 4 coxa smooth, antero-distally produced, anterior margin straight, distal margin rounded, posterior margin tapered. Pereopods 5-7 bases width length ratios 1: 1.5, 1: 1.3, 1:1.1, posterior margins smooth and setose; pereopods 5-6 bases with anterior and posterior margin nearly parallel, pereopod 7 basis posteriorly moderately produced.

Pleon: Epimeron 1 with 1 long anterodistal seta; epimeron 2 distal margin with 2 short setae; epimeron 3 bare, posteroventral corner subquadrate. Uropods 1-3 relative lengths 1.0: 0.7: 1.0. Uropod 1 peduncle subequal in length with inner ramus, outer ramus 0.9 × inner ramus length; inner ramus with 2 robust setae; outer ramus with 1 robust seta. Uropod 2 peduncle 0.9 × inner ramus length, outer ramus 0.7 × inner ramus length; inner and outer rami each with 2 robust setae. Uropod 3 peduncle 0.7 × inner ramus length, outer ramus 0.9 × inner ramus length; inner and outer rami each with 2 robust setae. Telson 1.9 × longer than wide, apex tridentate, beset with two short setae.

Female (sexually dimorphic characters): Gnathopod 1 basis distally expanded, anterior margin with 2 short setae, posterior margin bare; carpus anterior margin smooth. Gnathopod 2 mediofacial setal row reaching 0.8 × propodus length. Epimeron 1 with 2 anterodistal setae.

Color pattern: When alive this species has yellow antennae and a white snowflake pattern on coxa 4.

Ecology: This species was collected among coral rubble.

Relationships: Leucothoe cracentis sp. nov. resembles Leucothoe alata Barnard, 1959 , Leucothoe dentata Ledoyer, 1973 , Leucothoe lihue Barnard, 1970 , Leucothoe micronesiae Barnard, 1965 , Leucothoe rudicula White and Thomas, 2009 , in having round eyes, gnathopod 1 with stout carpus and short dactylus. L. cracentis is unique in having a strongly dentate gnathopod 1 carpus anterior margin. The distally truncate gnathopod 2 carpus is also shared with L. alata , L. lihue , L. rudicula , and Leucothoe venetiarum Soika, 1949 , but it is only serrate in L. cracentis sp. nov. The short mandibular palp article 3 is shared with L. alata , L. lihue , and L. micronesiae .

Distribution: Dongsha Atoll, Taiwan (this study).

Figures

Fig. 3. (A) Leucothoe obuchii White and Reimer, 2012a, male, KNW-Green-2B; (B) Leucothoe ouraensis White and Reimer, 2012b, female, KNW-Dongsha-2017-10c; (C) Leucothoe togatta White and Reimer, 2012b, male, KNW-Dongsha-2017-7d; (D) Leucothoe toribe White and Reimer, 2012b, female, KNW-Dongsha-2017-6b; (E) Leucothoe trulla White and Reimer, 2012a, male, KNW-Dongsha-2017- 8a; (F) Leucothoe batillum sp. nov., male, KNW-Dongsha-2017-3f; (G) Leucothoe cracentis sp. nov., female, KNW-Dongsha-2017-4b; (H) Paranamixis lunata sp. nov., male anamorph, KNW-Dongsha-2017-7a; (I) Paranamixis lunata sp. nov., female leucomorph, KNW- Dongsha-2017-9a.

Fig. 6. Leucothoe cracentis sp. nov. male holotype, scale bars represent 0.1 mm; (A) Habitus; (B) Antenna 1 enlarged; (C) Maxilla 2; (D) Maxilla 1; (E) Maxilliped; (F) Gnathopod 2 medial; (G) Gnathopod 1 medial: (H) Gnathopod 1 carpus enlarged.

Fig. 7. Leucothoe cracentis sp. nov. female paratype, scale bars represent 0.1 mm; (A) Gnathopod 2 medial; (B) Lower lip; (C) Epimeron 1-3; (D) left Mandible; (E) Gnathopod 1 medial; (F) Gnathopod 1 propodus and carpus enlarge(D); (G) Telson; (H) Telson enlarged.