Floresorchestia palau, Lowry, J. K., 2013

Lowry, J. K., 2013, New species of Floresorchestia from Micronesia living in unusual habitats (Crustacea, Amphipoda, Talitridae), Zootaxa 3737 (5), pp. 576-584 : 577-580

Floresorchestia palau sp. nov.

( Figs 1 , 2 )

Type material. Holotype, male, 3.5 mm, OUMNH.ZC. 2002-24 -0118, inside Pinchers Lagoon, western edge of Malakal Harbour, Malakal Island, Koror, Palau , Micronesia (07°20.407' N 134°25.755'E), light trap sample, sandy callianassid flat, 3 m depth, S. De Grave & C. Burras, night 27–28 May 2002.

Additional material examined. 1 female (dissected, lost), same locality as holotype. 19 specimens, AM P.88295, under leaf litter just above high tide mark underneath mangrove branches on sandy/silty beach, 50 m east of the end of the main road northern end of Pelelieu Island, Palau , Micronesia, (7°2'52"N 134°16'10"E), G. Towner, 2 April 2012.

Type locality. Inside Pinchers Lagoon, western edge of Malakal Harbour, sandy flat, 3 m depth (07°20.407' N, 134°25.755'E).

Etymology. Named for the type locality.

Habitat. Beach-hopper, living in the supralittoral zone beneath mangrove branches on sandy/silty beach and found at 3 m depth in marine environment.

Description. Based on holotype, male, 3.5 mm.

Head. Eye medium (1/5–1/3 head length). Antenna 1 short, slightly longer than article 4 of antenna 2 peduncle. Antenna 2 shorter than head and first 3 pereonites; peduncular articles slender, article 5 longer than article 4. Mandible left lacinia mobilis 4-dentate. Maxilla 1 with well developed palp. Maxilliped palp article 2 distomedial lobe well developed; article 4 reduced, button-shaped.

Pereon. Gnathopod 1 sexually dimorphic; subchelate; coxa smaller than coxa 2; posterior margin of merus (palmate lobe vestigial), carpus and propodus each with lobe covered in palmate setae, palmate lobes in male only; propodus subtriangular, anterior margin with 3 groups of robust setae; dactylus subequal in length to palm, palm transverse. Gnathopod 2 sexually dimorphic; subchelate; basis slightly expanded, anterior margin smooth; ischium with anterodistal cradle; merus with distally rounded posterodistal lobe on medial surface; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; carpus triangular, reduced (enclosed by merus and propodus), posterior lobe absent, not projecting between merus and propodus; propodus subovate, 1.6 × as long as wide; palm acute, reaching about 45% along posterior margin, smooth, lined with robust setae, posterodistal corner with groove, with cuticular patch at corner of palm; dactylus longer than palm, attenuated distally. Pereopods 2–4 coxae wider than deep, or as wide as deep. Pereopods 3–7 cuspidactylate. Pereopod 4 subequal or slightly shorter than pereopod 3; carpus similar in length to pereopod 3 carpus; dactylus similar to pereopod 3 dactylus. Pereopod 5 propodus distinctly longer than carpus. Pereopods 6–7 long, nearly 1/2 length of body, longer than pereopods 3–5. Pereopod 6 slightly shorter than pereopod 7; posterior lobe inner view posteroventral corner rounded, posterior margin perpendicular to ventral margin, posterior lobe without ridge, with 1–2 marginal setae. Pereopod 7 basis lateral sulcus absent, basis posterior margin with distinct minute serrations, each with a small seta, posterodistal lobe absent; merus and carpus slender; merus posterior margin evenly rounded; propodus setation without large distal tuft of setae.

Pleon. Pleopods1–3 all biramous, well developed. Epimera 2–3 each with vertical slits just above ventral margins. Epimera 2 with 17 slits, subequal in length to epimeron 3. Epimeron 3 with at least 12 slits, posterior margin smooth, without setae, posteroventral corner with small subacute tooth, ventral margin without setae. Uropod 1 peduncle with 6 robust setae, distolateral robust seta absent; inner ramus subequal in length to outer ramus, inner ramus with 2 marginal robust setae (1 row); outer ramus without marginal robust setae. Uropod 2 peduncle with 3 robust setae; inner ramus subequal in length to outer ramus, without marginal robust setae; outer ramus without marginal robust setae. Uropod 3 peduncle with 1 robust setae; ramus shorter than peduncle, linear (narrowing), with 3 apical setae. Telson about as broad as long, apically incised, dorsal midline entire, with 2 marginal and apical robust setae per lobe.

Female (sexually dimorphic characters). Gnathopod 1 posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; anterior margin with 2 groups of robust setae; palm slightly acute. 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, without cuticular patch at corner of palm; dactylus subequal in length to palm, not modified distally, blunt.

Remarks. Floresorchestia palau is characterised by a 4-dentate left lacinia mobilis, male gnathopod 1 with palmate lobes on the merus (vestigial), carpus and propodus, epimera 2–3 with vertical slits, and uropod 3 ramus without marginal setae. The only other similar species is F. hanoiensis Hou & Li, 2003 (Hou, pers com, has confirmed vertical slits on epimera 2 and 3). Floresorchestia palau differs from this species in a number of ways including having no setae on the rami of uropod 2 (setose in F. hanoiensis ), only one robust seta on the peduncle of uropod 3 (two in F. hanoiensis ) and only two setae per lobe on the telson (three in F. hanoiensis ).

Distribution. Micronesia. Palau .

Figures

FIGURE 1. Floresorchestia palau sp. nov., female, Pinchers Lagoon, western edge of Malakal Harbour, Koror, Palau, Micronesia.

FIGURE 2. Floresorchestia palau sp. nov., female, holotype, male, 3.5 mm, OUMNH. ZC. 2002 - 24 - 0118, Pinchers Lagoon, western edge of Malakal Harbour, Koror, Palau, Micronesia.