Tongorchestia towneri, 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 : 364-369

Tongorchestia towneri sp. nov.

( Figs 13–16 )

Type material. Holotype, male, 11.5 mm, AM P.89674 (on SEM stubs MI551–MI556). Paratypes: female AM P.89675 (SEM stub, MI557), 4 males, 4 females and juveniles, AM P.80739, Tufuvai Beach ‘Eua Island, Tonga (21°21.650’S 174 °58.143’W), supralittoral zone, Greg Towner, 27 September 2009; 8 females and juveniles, AM P.80740, Ha’aluma Beach, ‘Eua, Tonga (21°25.719’S 174°56.799’W), supralittoral zone, Greg Towner, 29 September 2009.

Additional material examined. 11 males, 34 females and juveniles, AM P.87321, fine sand under narrow fringe of mangroves near Nukuleka, Tongatapu, Tonga (21°09’12.75”S 175°07’43.66”W), dark brown talitrids under leaves and dead algae, J.K. Lowry & G.C.B. Poore, 15 October 2011.

Type locality. Tufuvai Beach ‘Eua, Tonga (21°21.650’S 174 °58.143’W), supralittoral zone.

Etymology. Named for Greg Towner, Australian Museum volunteer and collector of the species.

Habitat. Beach-hoppers, living among leaves and dead algae in the supralittoral zone.

Description. Based on holotype, male, 11.5 mm, AM P.89674.

Head. Eyes present. Antenna 1 short, not reaching end of article 4 of antenna 2 peduncle. Antenna 2 up to half body length; peduncular articles incrassate; article 5 subequal to article 4. 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; carpus 1.6 × as long as propodus, 3.1 × as long as broad; propodus 'subtriangular' with well developed posterodistal lobe, anterior margin with 5 groups of robust setae, lateral surface with 9 cuspidate setae, posterolateral surface with 6 serrate setae, medial surface with 7 cuspidate setae, posteromedial surface with 3 serrate setae, posterior margin without cuspidate setae, posterior margin without serrate setae; palm transverse, with 4 serrate setae; dactylus slightly longer than palm. 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 with lobe covered in palmate setae; carpus triangular, reduced (enclosed by merus and propodus), posterior lobe absent, not projecting between merus and propodus; propodus subrhomboidal, 1.3 × as long as wide; palm acute, reaching about 30% along posterior margin, lined with robust setae, evenly rounded, with small proximal sinus, without palmar protuberances; posteromedial surface of propodus with groove; with cuticular patch at corner of palm; dactylus subequal in length to palm, spatulate distally. Pereopods 2–4 coxae wider than deep. Pereopods 3–7 cuspidactylate; without distal patch of many rows of tiny denticles on the anterior margin. Pereopod 4 significantly shorter than pereopod 3; carpus significantly shorter than carpus of pereopod 3; dactylus thickened proximally with a notch midway along the posterior margin; dactylus without anterodistal patch. Pereopod 5 propodus distinctly longer than carpus. Pereopod 6 not sexually dimorphic, shorter than pereopod 7; coxa posterior lobe inner view posteroventral corner rounded, posterior margin perpendicular to ventral margin, posterior lobe with ridge, posterior lobe with 3–4 marginal setae; gill convoluted. Pereopod 7 not sexually dimorphic; basis lateral sulcus present, slightly pronounced, basis posterior margin with numerous small robust setae, posterodistal lobe present, shallow, broadly rounded; merus and carpus slender; merus posterior margin straight.

Pleon. Pleopods 1–3 well developed, biramous, rami multiarticulate, inner ramus subequal in length to outer. Epimeron 2 subequal in length to epimeron 3. Epimeron 3 posterior margin smooth, with tiny setae, posteroventral corner subquadrate, ventral margin without robust setae. Uropod 1 not sexually dimorphic, peduncle 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 5 marginal robust setae; outer ramus with marginal robust setae, with 4 robust setae on margins. Uropod 2 peduncle with 4 robust setae; inner ramus subequal in length to outer ramus, with 5 marginal robust setae; outer ramus with 2 marginal robust setae. Uropod 3 peduncle with 3 robust setae; ramus not fused to peduncle, subequal in length to peduncle, 2.2 × as long as broad, linear (narrowing), with 3 marginal robust setae, with more than 5 apical setae. Telson longer than broad, entire, dorsal midline vestigial or absent, with marginal and apical robust setae, with 7–9 robust setae per lobe.

Female (sexually dimorphic characters). Based on paratype, female, AM P.89675. Antenna 2 peduncular articles slender. Gnathopod 1 parachelate; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; propodus subrectangular, anterior margin with 3 groups of robust setae; palm acute, with 5 serrate setae. Gnathopod 2 mitten-shaped; basis expanded proximally; posterior margin of merus, carpus and propodus each with lobe covered in palmate setae; ischium without rounded lobe on mid-anterior margin; carpus well developed (not enclosed by merus and propodus), posterior lobe present, projecting between merus and propodus; palm obtuse, smooth, not lined with robust setae, without protuberance near dactylar hinge, posterodistal corner without spine; without cuticular patch at corner of palm; dactylus not modified distally.

Distribution. ‘Eua; Tongatapu; Tonga.

Figures

FIGURE 13. Tongorchestia towneri sp. nov., holotype, male, 11.5 mm, AM P. 89674, Tufuvai Beach ‘ Eua Island, Tonga. Scale lines for H, MD, MP, MX 1, UL, LL represent 100 µm; and MX 2 represents 20 µm.

FIGURE 14. Tongorchestia towneri sp. nov., holotype, male, 11.5 mm, AM P. 89674, Tufuvai Beach ‘ Eua Island, Tonga. Scale lines for G 1, P 3, P 4 represent 100 µm; and G 2, P 5, P 6, P 7 represent 200 µm.

FIGURE 15. Tongorchestia towneri sp. nov., paratype, female, AM P. 89675, Tufuvai Beach ‘ Eua Island, Tonga. Scale lines for G 1, G 2 represent 100 µm.

FIGURE 16. Tongorchestia towneri sp. nov., holotype, male, 11.5 mm, AM P. 89674, Tufuvai Beach ‘ Eua Island, Tonga. Scale lines for EP, Ur, U 1, U 2, U 3 & T represent 100 µm.