Floresorchestia trisetosa Suklom, Keetapithchayakul, Rahim & Wongkamhaeng, 2025, sp. nov.
Creators: name: Suklom, Anotai
name: Keetapithchayakul, Tosaphol Saetung
name: Rahim, Azman Abdul
name: Wongkamhaeng, Koraon
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Talitridae
Floresorchestia
Floresorchestia trisetosa

description: Floresorchestia trisetosa sp. nov.
Figs 3, 4, 5, 6
Type material.
Holotype • Thailand, 1 ♂; Muang Trat District, Trat; 12°15'12.9"N, 102°30'31.3"E; 21 February 2021; Anotai Suklom; pit fall trap; THNHM-lv-20866. Allotype • 1 ♀; collected with holotype; THNHM-lv-20867. Paratypes • 2 ♂ and 2 ♀ collected with holotype; THNHM-lv-20868.
Type locality.
A small creek near the restaurant, Muang Trat District, Trat, Thailand.
Ecological type.
Riparian hoppers (edges of lakes under stones or in very wet vegetation, near or in streams, rivers, creeks, cascades, and waterfalls).
Diagnosis.
Mandible lacinia mobilis 4 - dentate. Gnathopod 1 with palmate lobes on merus, carpus and propodus; palm acute. Gnathopod 2 propodus palm reaching ~ 33 % along posterior margin; dactylus attenuated distally. Pereopod 4 dactylus thickened proximally, with slight notch midway along posterior margin. Epimeron 2 and 3 with slits just above ventral margins. Uropod 1 outer ramus without marginal robust seta, with three marginal robust setae in one row. Uropod 3 peduncle with one robust seta; ramus with two apical robust setae. Telson with one apical robust seta, and two lateral robust seta per lobe.
Description.
Based on male holotype 8.7 mm, THNHM-lv-20866.
Head. Eye large (> 1 / 3 head length). Antenna 1 (Fig. 3, A 1) short, rarely longer than article 4 of antenna 2 peduncle. Antenna 2 (Fig. 3, A 2) <1 / 2 body length, peduncular articles slender, article 5 longer than article 4. Upper lip (Fig. 4, UL) without robust setae, broad, rounded apex, apical marginal with fine setule. Lower lip (Fig. 4, LL) without inner plate, with fine setule on apex and inner margin. Left mandible (Fig. 4, LMD) incisor 5 - dentate; left lacinia mobilis 4 - dentate and five pappose setae type I in one row; molar strong with 20 striations and one pappose setae type II on the distal of molar. Right mandible (Fig. 4, RMD) incisor 5 - dentate; lacinia mobilis with numerous cusps; molar strong with 26 striations and 1 distal pappose seta. Maxilla 1 (Fig. 4, MX 1) inner plate slender with 2 apical papposerrate setae type I; outer plate with 9 robust serrate setae type I and small palp 2 - articulate on outer lateral margin. Maxilla 2 (Fig. 4, MX 2) inner plate slightly shorter than outer plate, subapical margin with 19 robust setae, with one mediolateral papposerrate seta type I: outer plate with 18 apical robust setae in two rows. Maxilliped (Fig. 4, MP) inner plate apical and subapical margins with papposerrate setae type II, and two large conical robust setae; outer plate subapical margin with robust setae and two pappose setae; palp article 2 distomedial lobe well developed; article 4 reduced, button shaped.
Pereon. Gnathopod 1 (Fig. 3, G 1) sexually dimorphic; subchelate; coxa smaller than coxa 2, anterior margin slightly convex distally; basis slightly expanded posteriorly, anterior margin with four robust setae, posterior margin with two marginal robust setae and two terminal robust setae; ischium subquadrate, shortest, anterior lobe slightly rounded; posterior margin of merus, carpus and propodus each with lobe covered in palmate setae; carpus longer than propodus, carpus 1.27 × as long as propodus, carpus 1.9 × as long as broad; propodus ‘ subtriangular’ with well-developed posterodistal lobe, anterior margin with three groups of robust setae, lateral surface with four cuspidate setae, posterolateral surface with three serrate setae, medial surface with five cuspidate setae, posterior margin without cuspidate setae, with three serrate setae; palm transverse, with five serrate setae; dactylus longer than palm, without spine patch on posterodistal corner. Gnathopod 2 (Fig. 3, G 2) sexually dimorphic; subchelate; coxal gill simple (or slightly lobate); basis slightly expanded; ischium with distally rounded posterodistal lobe on medial surface; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; carpus reduced, enclosed by merus and propodus, posterior absent, not projecting between merus and propodus; propodus subovate, 1.4 × as long as wide; palm acute, reaching ~ 33 % along posterior margin, smooth, evenly rounded, lined with robust setae, posteromedial surface of propodus with groove, without cuticular patch at corner of palm; dactylus longer than palm, without anteroproximal bump, posterior margin smooth, attenuate distally; gill lobate.
Pereopods 3–4 (Fig. 5, P 3 – P 7) coxae wider than deep. Pereopods 3–7 cuspidactylate; dactyli without anterodistal patch of many rows of tiny setae. Pereopod 3 (Fig. 5, P 3) coxa wider than deep, ventral margin with four robust setae, posterior margin with acute process; basis slightly expanded, anterior margin slightly straight and naked, posterior margin with four robust setae; ischium subrectangular, shortest; merus longer than carpus and propodus, distally expanded, anterior margin with four robust setae, posterior margin with four robust setae; carpus as long as propodus, anterior margin with three setae, posterior margin with four robust setae; propodus slender, anterior margin with three robust setae, posterior margin with eight robust setae; dactylus without notch on posterior margin, anterior corner with one robust seta and posterior inner view with two robust setae. Pereopod 4 (Fig. 5, P 4) significantly shorter than pereopod 3; coxa wider than deep, posterior margin with acute process; basis slightly expanded distally, anterior margin distally convex, posterior margin with five robust setae; ischium shortest, subquadrate, distally convex; merus longer than carpus and propodus; carpus significantly shorter than carpus of pereopod 3; propodus slender, anterior margin with three groups of robust setae, posterior margin with three groups of robust setae; dactylus thickened proximally with a notch midway along posterior margin, dactylus without anterodistal setal patch. Pereopod 5 (Fig. 5, P 5) coxa bilobed, anterior lobe distinctly larger than posterior lobe, posterior lobe with setae on ventral margin; basis ovate, anterior margin with eight robust setae, posterior margin with five minute setae; ischium shortest, subrectangular, posterior margin distally convex; merus as long as carpus, distally expanded, anterior margin with five robust setae; carpus shorter than propodus, anterior margin with seven robust setae, posterior margin with one marginal robust seta and three robust setae distally; propodus distinctly longer than carpus; dactylus without anterodistal setal patch. Pereopods 6–7 (Fig. 5, P 6 and P 7) not sexually dimorphic. Pereopod 6 (Fig. 5, P 6) subequal in length to pereopod 7; coxa posterior lobe larger than anterior lobe, inner view posteroventral corner rounded, posterior margin perpendicular to ventral margin, posterior lobe without ridge, without marginal setae; basis ovate, anterior margin with eight robust setae, posterior margin with nine or ten minute setae; ischium shortest; merus slightly expanded, anterior margin crenulate with six robust setae, posterior margin convex with three robust setae; carpus as long as merus, anterior margin crenulate with eight robust setae, posterior margin with six robust setae in three groups; propodus longer than carpus, slender, anterior margin with eight robust setae in four groups, posterior margin with nine robust setae; dactylus slender with setae in posterior corner. Pereopod 7 (Fig. 5, P 7) coxa reduced; basis sub ovate, lateral sulcus absent, posterior margin with distinct minute serrations, each with a small seta, posterodistal lobe present, shallow, broadly rounded; ischium shortest, subrectangular with posterior rounded process; merus posterior margin expanded distally, subtriangular; propodus slightly longer than carpus, anterior margin with seven robust setae, posterior margin with eight robust setae and three terminal minute setae; dactylus slender and with subapical setae.
Pleon. Pleopods 1–3 well developed, biramous; peduncle ventral margin without robust setae; rami without ventral robust setae. Pleopod 1 (Fig. 6, PL 1) peduncle longer than rami; inner ramus subequal in length to outer ramus, with eight articles; outer ramus with nine articles. Pleopod 2 (Fig. 6, PL 2) peduncle longer than rami; inner ramus with eight robust setae; outer ramus with eight robust setae. Pleopod 3 (Fig. 6, PL 3) peduncle longer than rami; inner ramus with nine robust setae; outer ramus with seven robust setae. Epimeron 1 (Fig. 6, EP) posterior corner slightly projecting, and without slits. Epimera 2 and 3 each with slits above ventral margin; posterior ventral corner and ventral margin smooth. Uropod 1 (Fig. 6, U 1) peduncle slightly longer than ramus with 6 robust setae, distolateral robust seta present, small (<1 / 4 length of outer ramus), with simple tip; inner ramus subequal in length to outer ramus, inner ramus with three marginal robust setae (1 row), with four apical robust setae; outer ramus without marginal robust setae. Uropod 2 (Fig. 6, U 2) not sexually dimorphic; peduncle shorter than rami with 3 robust setae; inner ramus subequal in length to outer ramus, with marginal robust setae, with one lateral robust seta; outer ramus with marginal robust setae in one row. Uropod 3 (Fig. 6, U 3) peduncle longer than ramus with one robust seta; ramus not fused to peduncle; ramus 1.6 × as long as broad. Telson (Fig. 6, T) longer than broad, apically incised, dorsal midline less than halfway, with one apical robust seta, and two lateral robust setae.
Female (Fig. 6) (sexually dimorphic characters). Based on allotype, female 4.7 mm. THNHM-lv-20867.
Pereon. Gnathopod 1 (Fig. 6, G 1 ♀) parachelate; coxa anterior margin straight, anteroventral margin with three robust setae; basis slender, anterior margin straight, posterior margin slightly expanded distally with two subterminal robust setae; ischium shortest, subrectangular, anterior margin slightly convex; posterior margin of merus, carpus and propodus without lobe covered in palmate setae; merus triangular with two groups of robust setae on posterior margin; carpus subtriangular, anterior margin curved with four terminal setae, posterior margin slightly convex with three robust setae; propodus slender, anterior margin crenulate with two marginal robust setae and four terminal setae, posterior margin crenulate with three lateromedial robust setae; dactylus slender, anterior corner with one robust seta, posterior margin with one seta and two lateromedial robust setae. Gnathopod 2 (Fig. 6, G 2 ♀) mitten-shaped; coxa as long as deep, anterior margin straight, posterior margin straight, ventral margin with minute setae; basis expanded, anterior margin naked, posterior margin straight with one seta; ischium as long as merus, anterior margin with rounded lobe, posterior margin straight with one terminal seta; merus shorter than carpus, anterior margin with rounded lobe, posterior margin with rounded lobe; carpus and propodus each with lobe covered in palmate setae; carpus subtriangular, longer than propodus; propodus subovate, lateromedial corner with three robust setae; dactylus slender, shorter than palm, anterior margin with one robust seta, posterior margin with two robust setae.
Distribution.
Thailand. Trat town Municipality, Trat.
Etymology.
Named for the character of three robust setae on each telsonic lobe.
Remarks.
Floresorchestia trisetosa sp. nov. is closely related to F. boonyanusithii and F. amphawaensis by having the gnathopod 2 palm reaching between 31–35 %, dactylus posterior margin smooth, proximal tooth absent, and mandible left lacinia mobilis 4 - dentate. F. trisetosa can be separated from those two species by the combination of characteristics as follows (other species in paratheses): (1) gnathopod 1 carpus 1.2 × propodus (1.4 × in F. boonyanusithii, 1.5 × in F. amphawaensis); (2) uropod 1 peduncle with six robust setae (6 in F. boonyanusithii; 4 in F. amphawaensis); (3) uropod 3 peduncle with two robust setae (4 in F. amphawaensis and 2 in F. boonyanusithii); (4) telson longer than broad, telsonic lobe with three robust setae (vs 4 robust setae in F. boonyanusithii, and F. amphawaensis).
Floresochestia trisetosa is the first riparian hopper to be reported from Thailand (Fig. 7).
description: Published as part of Suklom, Anotai, Keetapithchayakul, Tosaphol Saetung, Rahim, Azman Abdul & Wongkamhaeng, Koraon, 2025, Two new species of riparian hoppers (Amphipoda, Talitridae) from Trat and Samut Prakan provinces, Thailand, pp. 369-396 in ZooKeys 1234 on pages 369-396, DOI: 10.3897/zookeys.1234.140645