Floresorchestia hanoiensis, Hou & Li, 2003

Hou, Z. - E. & Li, S., 2003, Terrestrial talitrid amphipods (Crustacea: Amphipoda) from China and Vietnam: studies on the collection of IZCAS, Journal of Natural History 37, pp. 2441-2460 : 2453-2459

Floresorchestia hanoiensis n. sp.

(figures 9–12)

Material examined. One male (holotype), 24 December 2000, Hanoi, Vietnam, collected by Shuqiang Li in pitfall traps. Sixteen males and 15 females (allotype and paratypes), the same collection data .

Etymology. The new species is named after its type locality, Hanoi, Vietnam.

Description. Male (  , IZCAS-I-A0016) 6.5 mm. Eyes subcircular, width about half of head. Buccal mass directed beneath head. Antenna 1 not reaching end of peduncular article 4 of antenna 2, peduncular articles 1–3 subequal in length; flagellum three-articulate, article 3 shortest. Antenna 2: peduncular articles 4–5 and its flagellum in length ratio 1.0:1.27:2.82, article 4 thicker than article 5, both with some spines along anterior and posterior margins; flagellum 12-articulate, each article armed with slender spinules.

Upper lip marginally rounded, with minute setae. Left mandible: incisor fivedentate, lacinia mobilis with five weak dentations, spinulate row with three stout spinulate setae, molar developed, with one seta. Right mandible: incisor five-dentate, ridge of lacinia mobilis with many weak teeth. Lower lip concave, with marginal setae. Maxilla 1: inner plate slender, shorter than outer plate, with two spinulate setae; outer plate with nine serrated spines; palp minute, two-articulate. Maxilla 2: inner plate with some long spinules on medial margin and a plumose seta, outer plate with many distal blunt setae and five slender spines near outer distal angle. Maxilliped: inner plate with three stout spines distally; article 4 of palp distinct, positioned latero-subdistally.

Gnathopod 1: lower margin of coxal plate rounded, with five small spines, row of spines on inner side near implantation of basis; basis straight, bearing one spine on outer margin and three short spines on inner margin; merus protuberant medialposteriorly, bearing three spines on base of protuberance; carpus and propodus tumescent posteriorly, carpus 1.72 times as long as propodus, bearing a pair of spines on dorsal margin and five slender spines along the tumescence; propodus distally expanded, armed with a row of spines on both faces, palm margin well exceeding dactylus, with some long setae medially; dactylus with a spine on curved margin and a stiff seta at joint of nail. Gnathopod 2: coxal plate with cuspidate posterior margin, ventral margin spinose; basis stout, posterior margin with three minute spines; propodus enlarged, palmar margin smoothly convex, fringed with many spines; dactylus beyond palm of propodus.

Pereopod 3 longer than pereopod 4, coxal plate with posterior cusp, ventral margin evenly armed with short spines; anterior margins of merus to propodus armed with fewer spines than posterior margins; dactylus cuspidactylate, with a stiff spine on concave margin. Pereopod 4 similar to pereopod 3, but posterior margin of coxal plate concave, cusp indistinct, carpus short.

Pereopod 5: coxal plate anterolobate, with four setae on posterior margin; basis moderately expanded; anterior margin of carpus and propodus with more spines than posterior margin; dactylus about 0.31 times as long as article 6. Pereopods 6 and 7 slender, articles increasing in length distally, dactylus cuspidactylate, bearing a spine at hinge of nail. Pereopod 6: coxal plate posterolobate with posterodistal seta, basis longish elliptic, dactylus about 0.34 times length of article 6. Pereopod 7: coxal plates non-lobate; basis strongly expanded posteriorly, posterior margin with many small setae; dactylus 0.37 times length of article 6.

Coxal gill of gnathopod 2 anchor-shaped. Coxal gills of pereopods 3 and 4 constricted. Coxal gills of pereopods 5 and 6 sac-like.

Epimeral plates 1–3 with slightly pointed posterior angles, ventral margin unarmed, posterior margin with single setule, surface ornamented with pits. Pleopods subequal in length, peduncles with two retinaculae, peduncle of pleopod 1 marginally bare, peduncle of pleopod 2 with several setae on outer distal margin, peduncle of pleopod 3 with many setae on outer medial margin and six minute spines on dorsal surface; outer ramus slightly longer than inner ramus, both rami armed with long plumose setae.

Uropod 1: peduncle longer than rami, with four spines on each margin; inner ramus with four single spines on outer margin; outer ramus a little shorter than inner ramus, marginally bare; both rami with distal spines. Uropod 2: peduncle with marginal spines, inner ramus with one mid-marginal and five distal spines, outer ramus with one mid-marginal and four distal spines. Uropod 3: peduncle with two subdistal spines; ramus narrower and shorter than peduncle, with three distal spines.

Telson apically notched, with one slender facial spine and two distal spines.

Dimorphism. Female (  , IZCAS-I-A0017), body 6.2 mm.

Gnathopod 1: carpus and propodus lacking tumescence, carpus 1.3 times as long as propodus, propodus parallel-sided, palm margin short, dactylus with a spine on concave margin and two setae at joint of nail. Gnathopod 2: coxal plate with cuspidate posterior margin, basis broadened anteroproximally, anterior margin setulose; merus with tumescence posteriorly, with one spine; carpus and propodus expanded, with tumescence posteriorly, propodus bearing two rows of spines on surface, palm armed with five spinules on medial margin; dactylus about half of propodus palm, with two setae on grasping margin and one seta at hinge of nail.

Brood plates of pereopods 2–5 parallel-sided, with few setae.

Habitat. This species was collected in pitfall traps in a small area of wasteland behind La Thanh Hotel in central Hanoi City, Vietnam. The pitfall traps were laid in the dry land because December is dry season in Vietnam. No river or other waters were observed in the proximity of the collection locality.

Remarks. Floresorchestia hanoiensis could be easily distinguished from the above three species by the following diagnostic characters: (1) article 4 of maxilliped distinct; (2) both merus of the male gnathopod 1 and merus of the female gnathopod 2 with tumescence on posterodistal margins; (3) posterior margin of pereopod 7 basis finely setulose; (4) epimeral plates with many irregular pits.

Floresorchestia hanoiensis differs from F. floresiana floresiana described from Fiji by Barnard (1960) in the peduncular articles 1 and 2 of antenna 1 being wider than long; the posterior margin of the coxal plate of pereopod 4 is concave, cusp indistinct; the peduncle of pleopod 3 has setulose posterior margin, rami attending 90% length of peduncle; the armature of epimeral plates spreading randomly, but in F. floresiana floresiana the armature of epimeral plates form a row along lower edge.