Floresorchestia boonyanusithii, Wongkamhaeng, Koraon, Dumrongrojwattana, Pongrat & Pattaratumrong, Manasawan Saengsakda, 2016

Wongkamhaeng, Koraon, Dumrongrojwattana, Pongrat & Pattaratumrong, Manasawan Saengsakda, 2016, Two new species of Floresorchestia (Crustacea, Amphipoda, Talitridae) in Thailand, ZooKeys 635, pp. 31-51 : 33-35

Floresorchestia boonyanusithii sp. n. Figures 1, 2, 3, 4, 5, Table 1

Type material.

Holotype. ♂, THAILAND, North-eastern Thailand, Phutsa Reservoir, Nakhon Ratchasima (15°2'59"N, 102°2'18"E), 21 Febuary 2016, Boonyanusith, C. PSUZC-CR-0310. Allotypes, ♀ collected with holotype; PSUZC-CR-0311; Paratype, collected with holotype (PSUZC-CR-0312 (5♂; 5♀))

Etymology.

Named after Chaichat Boonyanusith in appreciation of his contribution to the terrestrial amphipod study in Thailand.

Ecological type.

Land-hoppers (truly terrestrial). Size 5.5 mm. Sexual dimorphism present.

Description.

Based on male, holotype, 5.5 mm, PSUZC-CR 0310.

Head.Eye large (1/2 head length). Antenna 1 short, having four short articles of flagellum, extending one quarter ( ¼) of peduncle article 5. Antenna 2 peduncular articles slender; article 5 longer than article 4; flagellum of 13 articles, longer than peduncle, final article minute, without apical cluster of serrate setae. Upper lip broad, deep, apex rounded. Lower lip without inner plates. Left mandible incisor 4-dentate, lacinia mobilis 4-dentate, molar strong. Maxilla 1 inner plate slender with two terminal setae; outer plate with nine terminal serrate setae with small palp, 1-articulate. Maxilliped inner plate with apical and subapical plumose setae and three large conical robust setae; outer plate with two rows of subapical setae; palp article 2 distomedial lobe well developed; article 4 reduced, button-shaped.

Pereon.Gnathopod 1 sexually dimorphic; subchelate; coxa 1 smaller than coxa 2, ventral margin with six setae; posterior margin of merus, carpus and propodus each with a lobe covered in palmate setae, palmate lobes in male only; carpus 1.4 times as long as propodus, 2.6 times as long as broad; propodus subtriangular with well-de veloped posterodistal lobe, anterior margin with two groups of robust setae, posterior margin with four robust setae, palm with seven robust setae; dactylus cuspidactylate, subequal in length to palm.

Gnathopod 2 sexually dimorphic; subchelate; basis anterior margin smooth, widened distally; ischium with rounded lobe on mid-anterior margin; carpus triangular, reduced (enclosed by merus and propodus) without posterior lobe; propodus subovate, 1.5 times as long as wide; palm acute, extending 33% along posterior margin, lined with robust setae; dactylus longer than palm, attenuated distally, posterior margin smooth.

Pereopods 3-7 cuspidactylate. Pereopod 3 coxa subquadrate with posterior process, merus longer than carpus, distally expanded; propodus slender, longer than carpus. Pereopod 4 slightly shorter than pereopod 3; coxa wider than long with posterior process; carpus significantly shorter than carpus of pereopod 3; dactylus thickened proximally with a notch midway along the posterior margin. Pereopod 5 coxa bilobed, anterior lobe slightly larger than the posterior lobe; propodus distinctly longer than the carpus. Pereopods 6-7; pereopod 6 subequal in length to pereopod 7; coxa posterior lobe inner view posteroventral corner rounded, posterior margin perpendicular to ventral margin; coxal gill convoluted; propodus slender, longest; dactylus narrow. Pereopod 7; basis lateral sulcus absent, posterior margin with distinct minute serrations, each with a small seta, posterodistal lobe present, shallow, broadly rounded; merus and carpus distally expanded; carpus subrectangular propodus slender, longest; dactylus short.

Pleon.Pleopods all well developed. Pleopod 1 peduncle without marginal setae; biramous, inner ramus not longer than outer ramus, shorter than peduncle; inner ramus with seven articles; outer ramus with seven articles. Pleopod 2 peduncle without marginal setae; biramous, inner ramus subequal to outer, shorter than peduncle; inner ramus with eight articles; outer ramus with eight articles. Pleopod 3 peduncle without marginal setae; biramous, outer ramus shorter than peduncle; inner ramus with ten articles; outer ramus with eight articles.

Epimera 1-3 vertical slits present on plate 2 and 3. Epimera 2 with 27 slits. Epimera 3 with 20 slits. Epimeron 2 subequal in length to epimeron 3. Epimeron 3 posterior margin smooth, without setae, posteroventral corner with small subacute tooth, ventral margin without robust setae.

Uropod 1 peduncle with four robust setae, distolateral robust seta absent; inner ramus subequal in length to outer ramus, inner ramus with marginal robust setae (one row), with four marginal robust setae; outer ramus without marginal robust setae. Uropod 2 not sexually dimorphic; peduncle with three robust setae; inner ramus subequal in length to outer ramus, with marginal robust setae; outer ramus with marginal robust setae in one row, outer ramus with two marginal robust setae. Uropod 3 peduncle with two robust setae; ramus not fused to peduncle; ramus shorter than peduncle, 1.75 times as long as broad, ramus linear with three apical setae.

Telson longer than broad, apically cleft, dorsal midline half of the telson, with marginal and apical robust setae, four setae per lobe.

Female (sexually dimorphic characters).Gnathopod 1 coxa anterior margin straight; merus lacking tumescent lobe, posterior margin with five robust setae; propo dus without tumescent protuberance, anterior margin with two groups of robust setae; palm slightly acute, dactylus inner lateral posterior margin with one robust seta.

Gnathopod 2 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, not lined with robust setae, posterodistal corner without spine; dactylus subequal in length to palm, not modified distally, blunt.

Habitat.

Terrestrial, most prefer living in Typha angustifolia root near reservoir.

Distribution.

North-eastern Thailand.

Remarks.

Floresorchestia boonyanusithii sp. n. is the second land-hopper reported in Thailand. It can be distinguished from Floresorchestia samroiyodensis by the characters in the above key. Additionally, this species shows the following differences: 1) the left mandible lacinia mobilis has four cusps in both male and female (vs. male 4-dentate and female 6-dentate); 2) male gnathopod 1 carpus is 2.6 times longer than broad, 1.4 as long as propodus (vs. 2 times longer than broad, 1.8 times as long as propodus); 3) male gnathopod 2 propodus 1.4 times longer than broad, palm extending 39% along posterior margin (propodus 1.8 times longer than broad, palm extending 27% along posterior margin); 4) pereopod 7 is shallow, broadly rounded (vs. rounded, produced downwards almost to merus).

Floresorchestia boonyanusithii is characterised by a mandible left lacinia mobilis 4-dentate and uropod 3 peduncle with two robust setae. The only similar species are Floresorchestia buraphana sp. n. and Floresorchestia hanoiensis Hou & Li, 2003. The new species differs from Floresorchestia hanoiensis Hou & Li, 2003 in its pereopod 4 is thickened proximally with a notch midway along its posterior margin (vs. pereopod 4 similar to pereopod 3 dactylus) pereopod 7 basis shallow, broadly rounded (vs. produced downwards almost to merus); pleopod 1-3 peduncle without marginal robust setae; epimera 3 posterior margin without setae with 20 slits (vs epimera 3 posterior margin with five slits) and telson apically incised with four robust setae per lobe (vs. three robust setae per lobe).

Floresorchestia boonyanusithii shared several characters with Floresorchestia buraphana in having a mandible left lacinia mobilis 4-dentate; posterior margin of merus, carpus and propodus covered in palmate setae; uropod 3 peduncle with two robust setae and telson is longer than broad. Floresorchestia boonyanusithii differs from Floresorchestia buraphana in having uropod 3 rami without marginal setae (vs rami with one marginal seta) and telson with four robust setae per lobe (vs. five robust setae per lobe).