Floresorchestia pohnpei, 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 : 580-583

Floresorchestia pohnpei sp. nov.

( Figs 3–5 )

Type material. Holotype, male, 5.8 mm, AM P.85676, Nan Kepin Morap (lower site), Pohnpei , Micronesia (6°53'02.8''N 158°14'19.0''E), drift net, 435 m altitude, coll. Richard MacKenzie and Caitlin Kryss, 24 June, 2008 (APOD 012). Paratypes: 1 female, AM P.85677, 2 males, AM P.84220; 4 specimens, 3 males, 1 female, P.84217, Nan Kepin Morap (upper site), Pohnpei , Micronesia (6°53'08.2''N 158°14'17.3''E), surber net, 528 m altitude, coll. Richard MacKenzie and Caitlin Kryss, 4 February, 2009 (APOD 009); 4 specimens, 1 male (1 dissected), AM P.85678, 1 ma1e, 2 females, P.84218, Nan Pad (lower site), Pohnpei , Micronesia (6°51'19.7''N 158°13'05.1''E), drift net, 560 m altitude, coll. Richard MacKenzie and Caitlin Kryss, 10 July, 2008 (APOD 10); 4 specimens, 3 males, 1 female, P.84219, Male Komao, Pohnpei , Micronesia (6°51'01.6''N 158°14'01.0''E), surber net, 523 m altitude, coll. Richard MacKenzie and Caitlin Kryss, 18 February, 2009 (APOD 11).

Type locality. Freshwater stream, 435 m altitude, Nan Kepin Morap (lower site), Pohnpei , Micronesia (6°53'02.8''N 158°14'19.0''E).

Etymology. Named for the island where it lives.

Habitat. Stream-hoppers (truly aquatic fresh-water talitrids) living on the bottom of freshwater streams on the island of Pohnpei in Micronesia.

Description. Based on male, holotype, AM P.85676.

Head. Eye small (less than 1/5 head length). Antenna 1 short, longer than article 4 of antenna 2 peduncle. Antenna 2 less than half body length; peduncular articles slender, article 5 longer than article 4. Mandible left lacinia mobilis 4-dentate. Maxilla 1 with small palp, 1-articulate. Maxilliped palp article 2 distomedial lobe well developed; article 4 reduced, button-shaped.

Pereon. Gnathopod 1 sexually dimorphic; subchelate; coxa subequal in size to coxa 2; posterior margin of merus, carpus and propodus each with lobe covered in palmate setae; propodus subtriangular, anterior margin with 3 groups of robust setae, lateral surface without cuspidate setae, posterolateral surface with 6–7 serrate setae, medial surface with 7 cuspidate setae; palm with 4 serrate setae, dactylus subequal in length to palm, palm acute. Gnathopod 2 sexually dimorphic; subchelate; coxal gill lobate; basis slightly expanded; ischium with anterodistal cradle; 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; propodus subovate, 1.6 × as long as wide; palm acute, reaching 25% along posterior margin, smooth, lined with robust setae, posterodistal corner without spine, posteromedial surface of propodus with groove, without cuticular patch at corner of palm; dactylus longer than palm, attenuated distally. Pereopods 2–4 coxae as wide as deep. Pereopods 3–7 cuspidactylate; dactyli without anterodistal patch of many rows of tiny denticles. Pereopod 4 carpus similar in length to pereopod 3 carpus; dactylus slightly thickened proximally with a notch midway along posterior margin, dactylus without anterodistal patch. Pereopod 5 not sexually dimorphic; propodus distinctly longer than carpus; dactylus without anterodistal setal patch. Pereopods 6–7 long, 1/2 length of body, longer than pereopods 3–5. Pereopod 6 shorter than pereopod 7; posterior margin oblique to ventral margin, posterior lobe without ridge, posterior lobe without marginal setae. Pereopod 7 basis lateral sulcus absent, posterior margin with distinct minute serrations, each with a small seta, posterodistal lobe absent; merus and carpus slender; propodus setation without large distal tuft of setae.

Pleon. Pleopods biramous, all well developed. Epimera 1–3 vertical slits only present on epimeron 2. Epimera 2 longer than epimeron 3, with 25 slits. Epimeron 3 posterior margin smooth, without setae, posteroventral corner subacute/narrowly rounded, ventral margin without setae. Uropod 1 peduncle distolateral robust seta present, small (less than 1/4 length of outer ramus), with simple tip, without apical spear-shaped setae; inner ramus subequal in length to outer ramus, with 3 marginal robust setae in 1 row; outer ramus without marginal robust setae. Uropod 2 inner ramus longer than outer ramus, with 2 marginal robust setae; outer ramus without marginal robust setae.

Uropod 3 peduncle with 2 robust setae; ramus shorter than peduncle, ramus linear, narrowing, with 4–5 apical setae. Telson broader than long, apically incised, partially coalesced for most of length, dorsal midline entire, with 3 marginal and apical robust setae per lobe.

Female (sexually dimorphic characters). Gnathopod 1 posterior margin of carpus and propodus with cuticular patches; propodus medial surface without cuspidate setae; dactylus shorter than palm. Gnathopod 2 mitten-shaped; posterior margin of merus, carpus and propodus each with lobe covered in palmate setae; carpus well developed, posterior lobe projecting between merus and propodus; propodus twice as long as wide, palm obtuse, with cuticular surface; dactylus subequal in length to palm, not modified distally, blunt.

Remarks. Floresorchestia pohnpei sp. nov. has a weak cuticle for a talitrid. It is difficult to know which species F. pohnpei might align with. For instance the morphology of the male first gnathopod with the dactylus closing across the acute palm, is like no other known species. It is the third species of Floresorchestia with vertical slits only on epimeron 2. The other two species, F. australis Lowry & Springthorpe, 2009 and F. pectenispina (Bousfield, 1970) , both differ from F. pohnpei in having one long midmedial seta on the outer ramus of uropod 1 in adult males.

J.L. Barnard (1960) described a terrestrial species, Orchestia ponapensis (based on a female), from Mount Nahna Laud at about 610 m altitude, which is similar to F. pohnpei , but apparently has no vertical slits on the epimera.

Distribution. Western Pacific Ocean. Micronesia: Pohnpei .

Figures

FIGURE 3. Floresorchestia pohnpei sp. nov., holotype, male, 5.8 mm, AM P. 85676, Nan Kepin Morap (lower site), Pohnpei, Micronesia. Scales lines for MX 1, MX 2, MD represent 0.05 mm, remainder represent 0.1 mm.

FIGURE 4. Floresorchestia pohnpei sp. nov., holotype, male, 5.8 mm, AM P. 85676, paratype, female, AM P. 85677, Nan Kepin Morap (lower site), Pohnpei, Micronesia. Scale lines represent 0.1 mm.

FIGURE 5. Floresorchestia pohnpei sp. nov., holotype, male, 5.8 mm, AM P. 85676, Nan Kepin Morap (lower site), Pohnpei, Micronesia. Scale line represents 0.5 mm.