Talorchestia spinipalma ( Dana, 1852 )

Lowry, J. K. & Bopiah, Arundathi, 2013, The talitrid amphipods of Tonga (Crustacea, Amphipoda, Talitridae), Zootaxa 3681 (4), pp. 347-370 : 354-358

Talorchestia spinipalma ( Dana, 1852)

( Figs 5–8 )

Orchestia spinipalma Dana, 1852: 203 .— Dana, 1853: 875, pl. 59, fig. 4a-e.— Bate, 1862: 28, pl. 4, fig. 9. Talorchestia spinipalma .— Stebbing, 1906: 552 (in part, part = T. terraereginae ).— Stephensen, 1935: 12.— Schellenberg, 1938: 66.— J.L. Barnard, 1960: 24, figs 7, 8.— Bousfield, 1970: 163.— Morino & Miyamoto, 1988: 95, figs 4–6.— Lowry & Springthorpe, 2009: 905.— Serejo, 2009: 895, figs 3, 4.

Not Talorchestia spinipalma .— Lowry & Stoddart, 2003: 276 (= T. terraereginae ).

Type. Neotype, male, 16.5 mm, AM P.87317, fine white sand on steep narrow beach just north of Liku’alofa Beach Resort, Tongatapu, Tonga (21°04’50.29”S 175°20’39.10”W), white talitrids under dried Turbinaria and other algae, J.K. Lowry & G.C.B. Poore, 14 October 2011.

Additional material examined. 27 males, 41 females and juveniles, AM P.87322, coral rubble on white sand, Ene’io Beach, Vava’u, Tonga (18°38’15.15”S 173°54’39.04”W), J.K. Lowry & G.C.B. Poore, 12 October 2011; 1 female, AM P.87318, 33 males, 235 females and juveniles, AM P.87324, same collection data as neotype; 7 males, 40 females and juveniles, AM P.87323, wide fine sand beach backed by coral cliffs, with steep slope near the water, ‘Oholei Beach, Tongatapu, Tonga (21°14.265’S 175°05.993’W), white talitrids under Turbinaria , red algae forming a continuous line at top of slope, J.K. Lowry & G.C.B. Poore, 15 October 2011.

Type locality. Liku’alofa Beach Resort, Tongatapu, Tonga (~ 21°8'0''S 175°12'0''W).

Habitat. Beach-hopper living on fine white sands under supralittoral wrack.

Description. Based on neotype, male, 16.5 mm, AM P.87317. Head. Eye medium (1/5–1/3 head length). Antenna 1 short, rarely longer than article 4 of antenna 2 peduncle. Antenna 2 more than half body length; peduncular articles slender; article 5 longer than article 4. Mandible left lacinia mobilis 5-dentate. Maxilliped palp article 2 distomedial lobe well developed; article 4 fused with article 3.

Pereon. Gnathopod 1 sexually dimorphic; parachelate; coxa smaller than coxa 2; posterior margin of carpus and propodus each with lobe covered in palmate setae; propodus subrectangular, anterior margin with 6 groups of robust setae, posterolateral surface with 7 serrate setae, posterior margin without cuspidate setae, posterior margin with 5 serrate setae; palm transverse, with 3 serrate setae; dactylus longer than palm. Gnathopod 2 sexually dimorphic; subchelate; basis slender; ischium with slight anterodistal cradle; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; 1.8 × as long as wide; palm acute, reaching about 60% along posterior margin, weakly toothed, incised or sinuous, lined with 2 rows of robust setae, with rounded protuberance near dactylar hinge, posteromedial surface with groove; without cuticular patch at corner of palm; dactylus subequal in length to palm; gill simple, not incised. Pereopods 2–4 coxae wider than deep. Pereopods 3–5 gills larger than gill 2, smaller than gill 6. Pereopods 3–7 cuspidactylate; dactyli with anterodistal patch of about 20 rows of tiny setae. Pereopod 4 significantly shorter than pereopod 3; carpus significantly shorter than carpus of pereopod 3; dactylus thickened proximally with a notch midway along posterior margin; without anterodistal patch. Pereopod 5 propodus distinctly longer than carpus. Pereopod 6 shorter than pereopod 7; coxa posterior lobe inner view posteroventral corner rounded, posterior margin oblique to ventral margin, posterior lobe with ridge, posterior lobe with 1–2 marginal setae; gill simple, coxa not incised. Pereopod 7 basis lateral sulcus present, slightly pronounced, posterodistal lobe absent; merus and carpus slender; merus posterior margin straight.

Pleon. Pleopods 1–3 well developed; biramous. Pleopod 1 peduncle with marginal robust setae; outer ramus shorter than peduncle. Epimeron 2 subequal in length to epimeron 3. Epimeron 3 posterior margin smooth, with minute setae, posteroventral corner with small subacute tooth, ventral margin without robust setae. Uropod 1 not sexually dimorphic, peduncle with 18–19 robust setae, distolateral robust seta present, small (less than 1/4 length of outer ramus), with simple tip; inner ramus subequal in length to outer ramus, with 10 marginal robust setae in two rows; outer ramus without marginal robust setae. Uropod 2 not sexually dimorphic; peduncle with 6 robust setae; inner ramus subequal in length to outer ramus, with 6 marginal robust setae; outer ramus with 2 marginal robust setae. Uropod 3 peduncle with 9 robust setae; ramus shorter than peduncle, ramus linear (narrowing distally), ramus with 4–5 marginal robust setae, ramus with 3 apical setae. Telson as broad as long, apically incised, dorsal midline entire, with marginal and apical robust setae, with 7–8 robust setae per lobe.

Female (sexually dimorphic characters). Based on female, AM P.87318. Gnathopod 1 posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; propodus anterior margin with 4 groups of robust setae, posterior margin with 3 cuspidate setae; posterior margin with 2–3 serrate setae. Gnathopod 2 chelate; basis expanded anteroproximally; ischium without posterodistal lobe on medial surface; posterior margin of carpus and propodus each with lobe covered in palmate setae; carpus well developed (not enclosed by merus and propodus), posterior lobe present, projecting between merus and propodus; 3.5 × as long as wide; palm obtuse, smooth, lined with small robust setae, without protuberance or shelf near dactylar hinge.

Remarks. There are several species ( T. mindorensis Oleröd, 1970 , T. spinipalma Dana, 1852 and T. terraereginae Haswell, 1880 ) with a distinctive rounded protuberance on the palm of male gnathopod 2. Apparently only T. spinipalma has the carpus and propodus of male gnathopod 2 fused.

Among the records of T. spinipalma from the South Pacifc there are four relatively well illustrated populations: J.L. Barnard 1960 (Kosrae, Micronesia); Morino & Miyamoto 1988 (Motupore, Papua New Guinea); and Serejo 2009 (Port Denison, Australia). Neither Schellenberg (1938) nor Bousfield (1970) illustrated specimens from their collections and they remain unconfirmed. Table 1 indicates morphological differences between these populations. Adult males from Tonga appear to be significantly larger than males of other reported populations yet the telson has significantly fewer robust setae and is as long as broad. For the moment we prefer to keep these populations under one name until more information is available, although the Tongan population might be considered the most distinct.

Currently T. spinipalma appears to be a widespread tropical western South Pacific island species. The possibility remains that this is a complex of cryptic species. If this is the case then they appear to be sister taxa and the question remains, how did they become dispersed. Hughes (pers comm) has suggested that they were moved from island to island in Polynesian ocean-going canoes during the past 3000 years much as food plants such as kumara and taro. But the records from Queensland and New Caledonia are problematic because apparently Polynesians never landed in either place. The possibility that T. spinipalma has been rafted on floating algal mats (see Thiel & Haye 2006) might be considered, but talitrids have apparently never been collected on floating wrack ( Wildish 2012).

Length Male G 1 Male G 1 Male G 2 Male G2 Telson Telson mm carpus> propodus ischium palm to length / setae per propodus Ln to Br lobe post. marg. breadth lobe Distribution. Australia. Queensland: Port Douglas ( Serejo 2009). Marshall Islands. Yap; Kusaie Island ( J.L. Barnard 1960). New Caledonia. Nou Vata, Noumea; Ile of Pines ( Morino & Miyamoto 1988). Papua New Guinea. Ralum, Bismarck Archipelago ( Schellenberg 1938); Motupore Island (9°31’30”N 147°16’40”E) ( Morino & Miyamoto 1988). Philippine Islands. Ubay, Bohol ( Schellenberg 1938). Solomon Islands. Gizo ( Morino & Miyamoto 1988); Rennell Islands: ( Bousfield 1970). Tonga. Tongatapu ( Dana 1852; this paper).

Figures

FIGURE 5. Talorchestia spinipalma (Dana, 1852), neotype, male, 16.5 mm, AM P. 87317, Liku’alofa Beach Resort, Tongatapu, Tonga. Scale lines for rMd, lMd, MX 1 represent 20 µm; and H, UL, LL, MX 2, MP represent 100 µm.

FIGURE 6. Talorchestia spinipalma (Dana, 1852), neotype, male, 16.5 mm, AM P. 87317, female, AM P. 87318, Liku’alofa Beach Resort, Tongatapu, Tonga. Scale lines for male G 1, female G 1 & G 2 represent 100 µm; and male G 2 represents 200 µm.

FIGURE 7. Talorchestia spinipalma (Dana, 1852), neotype, male, 16.5 mm, AM P. 87317, Liku’alofa Beach Resort, Tongatapu, Tonga. Scale lines for P 3, P 4, P 5, P 6 & P 7 represent 200 µm.

FIGURE 8. Talorchestia spinipalma (Dana, 1852), neotype, male, 16.5 mm, AM P. 87317, Liku’alofa Beach Resort, Tongatapu, Tonga. Scale lines for EP, U 1, U 2, U 3 & T represent 100 µm; and Ur represents 200 µm.