Tongorchestia pangaimotu, Lowry, J. K. & Bopiah, Arundathi, 2013

Lowry, J. K. & Bopiah, Arundathi, 2013, The talitrid amphipods of Tonga (Crustacea, Amphipoda, Talitridae), Zootaxa 3681 (4), pp. 347-370 : 359-364

Tongorchestia pangaimotu sp. nov.

( Figs 9–12 )

Type material. Holotype, male, 9.6 mm, AM P.87315, under dead Zostera on coarse sand flat on east side of causeway, Holeva, Vava’u, Tonga (18°38.374’S 173°55.199’W), pigs rooting in the shallow water near the site, J.K. Lowry & G.C.B. Poore, 12 October 2011. Paratypes: female, AM P.87316, same data as holotype; 22 males, 55 females and juveniles, AM P.87320, same data as holotype.

Additional material examined. 6 males, 17 females and juveniles AM P.87319, small sheltered coral rubble beach immediately backed by forest, Pangaimotu Island where causeway connects Pangaimotu Island to Vava’u, Tonga (18°40.825’S 173°59.144’W), talitrids under leaf litter. Evidence of pigs rooting on beach, J.K. Lowry & G.C.B. Poore, 11 October 2011; 8 specimens, AM P.80737, between Vava’u Island and Pangaimotu Island, Tonga (18°41’S 173°59’W), Greg Towner, 19 September 2009.

Type locality. East side of causeway, Holeva, Vava’u, Tonga (18°38.374’S 173°55.199’W), under dead Zostera on coarse sand flat, supralittoral zone.

Etymology. Named for the type locality, Pangaimotu Island.

Colour. Second antennae dark orange, dark orange stripe running across the body on each segment.

Habitat. Beach-hopper living in the supralittoral zone on sheltered coral rubble and coarse sand beaches.

Description. Based on holotype, male, 9.6 mm, AM P.87315.

Head. Eye present. Antenna 1 short, rarely longer than article 4 of antenna 2 peduncle. Antenna 2 less than half body length; peduncular articles incrassate, article 5 subequal in length to article 4, peduncular articles with many small robust setae, final article cone-shaped, with apical cluster of 'imbricated' setae. Lower lip with vestigial inner plates. Mandible left lacinia mobilis 4-dentate. Maxilla 1 with small palp, 2-articulate. 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 carpus and propodus each with lobe covered in palmate setae; basis with group of anteroproximal setae; carpus 1.6 × as long as propodus, carpus 2.8 × as long as broad; propodus 'subtriangular' with well developed posterodistal lobe, anterior margin with 4 groups of robust setae, posterolateral surface with 5 serrate setae, posterior margin without cuspidate setae, posterior margin without serrate setae; dactylus subequal in length to palm, palm transverse, without spine patch on posterodistal corner; dactylus simplidactylate, without anterodistal setal patch. Gnathopod 2 sexually dimorphic; subchelate; basis slender; ischium with rounded lobe on mid-anterior margin, without 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; propodus subquadrate, as long as wide; palm slightly acute, reaching about 25–27% along posterior margin, smooth, evenly rounded, lined with robust setae, posteromedial surface of propodus with groove, with cuticular patch at corner of palm; dactylus slightly longer than palm, curved, without anteroproximal bump, posterior margin with posteroproximal projections, attenuated distally. Pereopods 2–4 coxae wider than deep. Pereopods 3–7 cuspidactylate; dactyli without anterodistal patch of many 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. Pereopod 5 propodus subequal to or slightly shorter than carpus. Pereopods 6–7 not sexually dimorphic. Pereopod 6 slightly shorter than pereopod 7; coxa posterior lobe inner view posteroventral corner rounded, posterior margin perpendicular to ventral margin, posterior lobe with ridge. Pereopod 7 basis lateral sulcus present, slightly pronounced, posterior margin with numerous small robust setae, posterodistal lobe present, shallow, broadly rounded; distal articles (merus and carpus) slender; merus posterior margin evenly rounded.

Pleon. Pleopods 1–3 well developed, biramous, rami multiarticulate, inner ramus subequal in length to outer. Pleopod 3 peduncle with marginal robust setae; outer ramus with 7 articles. Epimeron 2 slightly longer than epimeron 3. Epimeron 3 posterior margin smooth, with tiny setae, posteroventral corner subquadrate, ventral margin without robust setae. Uropod 1 peduncle with 12 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, inner ramus with 4 marginal robust setae in 1 row; outer ramus with 4 marginal robust setae. Uropod 2 peduncle with 3 robust setae; inner ramus subequal in length to outer ramus, with marginal robust setae in 2 rows, with 3 lateral and 2 medial robust setae; outer ramus with 2 marginal robust setae in 1 row. Uropod 3 peduncle with 3 robust setae; ramus partially fused to peduncle, shorter than peduncle, 3.3 × as long as broad, linear (narrowing distally), with 3 marginal robust setae, with more than 5 apical setae. Telson as broad as long, apically incised, dorsal midline entire, with 12–13 marginal and apical robust setae per lobe.

Female (sexually dimorphic characters). Based on paratype, female, AM P.87316. Gnathopod 1 parachelate; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; carpus 2.5 × as long as broad; propodus subrectangular; without serrate setae; dactylus longer than palm. Gnathopod 2 mitten-shaped; basis expanded anteroproximally; ischium without lobe on anterior margin; posterior margin of merus, 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; 1.4 × as long as wide; palm obtuse, nearly straight, not lined with robust setae, without cuticular patch at corner of palm; dactylus subequal in length to palm, posterior margin smooth. Oostegites longer than wide, weakly setose, setae with simple smooth tips.

Remarks. Tongorchestia pangaimotu is smaller (9.6 mm) as T. towneri (11.5 mm) with a 2-articulate palp on maxilla 1 (1-articulate in T. towneri ), with telson about as long as broad (longer than broad in T. towneri ), apically incised with entire dorsal midline and 12–13 robust setae per lobe (entire in T. towneri with vestigial dorsal midline and 7–8 setae per lobe). Tongorchestia pangaimotu is unusual in that the peduncle and ramus of uropod 3 is fused.

Distribution. Vava’u, Tonga.

Figures

FIGURE 9. Tongorchestia pangaimotu gen. nov., sp. nov., holotype, male, 11.8 mm, AM P. 87315, Holeva, Vava’u, Tonga. Scale lines for A 1, A 2, MP, LL, MX 2 represent 100 µm; and MD, MX 1 represent 20 µm.

FIGURE 10. Tongorchestia pangaimotu gen. nov., sp. nov., holotype, male, 11.8 mm, AM P. 87315, female, AM P. 87316, Holeva, Vava’u, Tonga. Scale lines for male and female G 1 & G 2 represent 100 µm.

FIGURE 11. Tongorchestia pangaimotu gen. nov., sp. nov., holotype, male, 11.8 mm, AM P. 87315, Holeva, Vava’u, Tonga. Scale lines for P 3, P 4, P 5 & P 7 represent 200 µm; and P 6 represents 100 µm.

FIGURE 12. Tongorchestia pangaimotu gen. nov., sp. nov., holotype, male, 11.8 mm, AM P. 87315, Holeva, Vava’u, Tonga. Scale lines for EP, Ur, U 2, U 3, T represent 100 µm.