Floresorchestia amphawaensis sp. nov.

Type material.

Holotype. ♂, 7.8 mm, THNHM-lv-18763, THAILAND, Amphawa District, Samut Songkhram, Thailand (13°26'27.8"N, 99°57'41.3"E), 21 February 2021, Piyangkun Lueangjaroenkit; THNHM-lv-18764. Allotypes, ♀ collected with holotype; THNHM-lv-18764; Paratypes 5 ♂ and 10 ♀ collected with holotype; THNHM-lv-18765.

Type locality.

man-made ditch in coconut plantation, Amphawa District, Samut Songkhram, Thailand (13°26'27.8"N, 99°57'41.3"E).

Habitat.

Riparian-hoppers living near agricultural and urban areas in Amphawa District.

Etymology.

Named for the District of Samut Songkhram, Thailand where the species occurs.

Ecological type.

Riparian-hoppers (edges of lakes under stones or in very wet vegetation, near (or in) streams, rivers, creeks, cascades and waterfalls).

Description.

Based on holotype, male, 7.8 mm, THNHM-lv-18763.

Head (Fig. 3FA) Eye large (greater than 1/2 the length of the head). Antenna 1 (Fig. 4A1) short, rarely longer than article 4 of antenna 2 peduncle. Antenna 2 (Fig. 4A2) shorter than half body length; peduncular article slender; article 3 shortest; article 5 longer than article 4; flagellum with 13 articles, final article cone-shaped with an apical cluster of setae.

Upper lip (Fig. 5UL) broad, deep, apex rounded, without robust setae. Lower lip (Fig. 5LL) present; without inner plates. Left mandible (Fig. 5LMD) incisor 6-dentate; lacinia mobilis 4-dentate and four plumose setae in one row; molar strong with 16 striations and one plumose seta. Right mandible (Fig. 5RMD) incisor 5-dentate; lacinia mobilis with numerous cusps, group of three robust setae and cluster of fine setae; molar strong with 18 striations and one plumose seta. Maxilla 1 (Fig. 5MX1) inner plate slender with two terminal plumose setae; outer plate with seven robust serrated setae; with small 1-articulate palp. Maxilla 2 (Fig. 5MX2) plates narrow, inner plate slightly shorter than outer; with 14 subapical robust setae, one plumose seta and 9 facial setae; outer plate with 18 apical robust setae in two rows and five simple setae in outer corner. Maxilliped (Fig. 5MP) inner plate apical and subapical margins with plumose setae, robust setae and two large conical robust setae; outer plate with two rows subapical setae and plumose setae; palp article 2 distomedial lobe well developed with numerous setae; article 4 reduced, button-shaped.

Pereon. (Figs 4, 6) Gnathopod 1 (Fig. 4G1) sexually dimorphic; subchelate, coxa smaller than coxa 2, ventral margin lined with five robust setae, anterior margin straight; basis expanded posteriorly, anterior margin with four setae, posterodistal margin with two setae; posterior of merus, carpus and propodus each with lobe covered in palmate setae; carpus 1.5 × longer than propodus, anterior margin with two robust setae, posterior margin with four robust setae; propodus subtriangular with well-developed posterior lobe, anterior side with three groups of coupled robust setae, posterior margin with five robust setae, palm slightly serrated, lined with nine robust setae; dactylus cuspidactylate, shorter than palm.

Gnathopod 2 (Fig. 4G2) sexually dimorphic; subchelate; coxa anterior margin with two setae and ventral margin with seven setae; basis anterior margin smooth, slightly expanded, posterior margin with three robust setae; ischium with rounded lobe on anterior margin; posterior of merus, carpus and propodus glabrous; carpus triangular, reduced, enclosed by merus and propodus, posterior lobe absent; propodus subovate, 1.4 × as long as wide, palm reaching about 34%, posteromedial surface of propodus with groove, anterior side naked, palm lined with 11 robust setae; dactylus longer than palm fitted with facial groove, attenuated distally.

Pereopod 3 (Fig. 6P3) coxa longer than broad with posterior process, anterior margin with seven robust setae; basis slightly expanded, anterior margin with three robust setae, posterior margin with three robust setae; ischium shortest; merus longer than ischium, anterior and posterior margin of merus lined with clusters of robust setae; carpus and propodus slightly expanded; carpus posterior margin with cluster of robust setae; dactylus without notch on posterior margin.

Pereopod 4 (Fig. 6P4) slightly shorter than pereopod 3; coxa longer than broad, anterior margin with five robust setae and with small posterior process; basis longest, posterior margin with three robust setae; ischium shortest, posterodistal with two robust setae; merus and carpus shorter than those of pereopod 3; merus distally expanded, longer than carpus and propodus, anterior and posterior margin with five robust setae; carpus shorter than propodus posterior margin with three clusters of robust setae; propodus slender, with three clusters of robust setae in posterior side; dactylus slender and longer than that of pereopod 3, thickened proximally with a notch along posterior margin.

Pereopod 5 (Fig. 6P5) coxa bilobed, anterior lobe distinctly large than posterior lobe; basis anterior margin with five robust setae, posterior margin with row of tiny setae; merus and carpus distally expanded; carpus shorter than propodus; propodus slender, longer than merus and carpus.

Pereopod 6 (Fig. 6P6) coxa bilobed, posterior lobe larger than anterior; basis expanded, anterior margin with 10 robust setae, posterior margin with row of tiny setae; ischium shortest; merus distally expanded, anterior side with four clusters of robust setae; carpus expanded less than merus, anterior margin lined with four clusters of robust setae; propodus slender, longer than merus and carpus; dactylus slender with subapical robust setae.

Pereopod 7 (Fig. 6P7) coxa reduced; posterior margin of basis with distinct minute serration (each serrate with small seta), anterior margin with 10 robust setae; merus and carpus slightly expanded; propodus longer than each merus and carpus; dactylus slender with subapical robust setae.

Pleon. (Fig. 7) Pleopods all well developed. Pleopod 1 (Fig. 7PL1) peduncle without marginal setae; biramous, outer ramus subequal in length to peduncle; inner ramus with 11 articles; outer ramus with seven articles. Pleopod 2 (Fig. 7PL2) peduncle without marginal setae; biramous, inner ramus subequal to outer ramus, shorter than peduncle; inner ramus with seven articles; outer ramus with six articles. Pleopod 3 (Fig. 7PL3) peduncle without marginal setae; biramous, inner ramus subequal to outer ramus, shorter than peduncle; inner ramus with nine articles; outer ramus more than six articles.

Epimera (Fig. 7EP), Epimeron 1 posterodistal corner slightly protruding, without slit. Epimera 2 and 3 each with slits above ventral margin, with 21 and 10 slits, respectively. Epimeron 3 posteroventral corner and ventral margin smooth.

Uropod 1 (Fig. 7U1) peduncle with four robust setae in one row; inner ramus subequal in length to outer ramus, inner ramus with five marginal robust setae, apical with three robust setae; outer ramus without marginal robust setae, apical with three robust setae. Uropod 2 (Fig. 7U2) peduncle with three robust setae; inner ramus subequal in length to outer ramus; inner ramus with two marginal robust setae, apical with four robust setae; outer ramus with one marginal robust seta, apical with two robust setae. Uropod 3 (Fig. 7U3) uniramous, peduncle with four robust setae; ramus subequal to peduncle, without marginal robust setae and three apical robust setae.

Telson (Fig. 7TL) as long as broad, weakly cleft, dorsal mid-line at least halfway, with one marginal, three apical robust setae and two plumose setae.

Female (Sexually dimorphic characters) (Fig. 8). Type. Allotype, female, 8.9 mm, THNHM-lv-18764.

Pereon. Gnathopod 1 (Fig. 8G1) merus lacking tumescent lobe, posterior margin with three robust setae; propodus without tumescent protuberance, anterior margin with three clusters of robust setae, posterior margin with six robust setae; palm slightly transverse, dactylus inner lateral posterior margin with four robust setae.

Gnathopod 2 (Fig. 8G2) mitten-shaped; posterior margin of carpus and propodus each with lobe covered in palmate setae; carpus well developed, posterior lobe projecting between merus and propodus; nearly twice as long as wide; palm obtuse, lined with 10 robust setae, posterodistal corner with two robust setae; dactylus not modified distally, blunt.

Remarks.

Floresorchestia amphawaensis sp. nov. is similar to F. malayensis with which they share characteristics such as: (1) left mandible lacinia mobilis with 4-dentate; (2) gnathopod 1 carpus longer by 1.5 × than propodus; (3) gnathopod 2 dactylus posterior margin smooth; (4) gnathopod 2 propodus 1.4 × as long as wide; (5) uropod 1 peduncle with 4-6 robust setae; (6) uropod 3 ramus without marginal setae; (7) telson with four robust setae per lobe; (8) epimera 2-3 with slits. However, F. amphawaensis sp. nov. may be distinguished from F. malayensis by the following [Characters of F. malayensis in brackets]: (1) gnathopod 2 palm reaching 34% [palm reaching 30%]; (2) uropod 1 inner ramus with five marginal setae [four marginal setae]; (3) uropod 1 peduncle with four robust setae [with five robust setae]; (4) uropod 3 peduncle with four robust setae [two robust setae]; (5) telson slightly longer than broad [broader than long].