Tongorchestia borabora, Lowry, J. K. & Bopiah, Arundathi, 2014

Lowry, J. K. & Bopiah, Arundathi, 2014, A new species of Tongorchestia from Bora Bora in the leeward Society Islands (Crustacea, Amphipoda, Talitridae), Zootaxa 3784 (3), pp. 251-258 : 251-257

Tongorchestia borabora sp. nov.

( Figs 1–5 )

Type material. Holotype, male, 9.7 mm, AM P.92565 supralittoral, strandline debris, Bay of Faaopore, near Club Mediterranee, Viatape, Bora Bora, Society Islands (16°30'S 151°45'30"W), A.A. Myers, 29 December, 1986. Paratypes: female, AM P.92566; 11 specimens, AM P.38809, same data as holotype.

Type locality. Supralittoral, strandline debris, Bay of Faaopore, near the old Club Mediterranee, Viatape, Bora Bora, Society Islands (16°30'S 151°45'30"W).

Etymology. Named for the type locality, Bora Bora.

Habitat. Living among strandline debris in the supralittoral zone.

Description. Based on holotype, male, 9.7 mm, AM P.92565.

Head. Head with five groups of long, slender scales along ventroproximal surface. Antenna 1 short, rarely longer than article 4 of antenna 2 peduncle. Antenna 2 less than half body length; peduncular articles incrassate (expanded), article 5 subequal in length to article 4, peduncular articles with many large robust setae; flagellar articles final article cone-shaped, with apical cluster of 'imbricated' setae. Mandible left lacinia mobilis 4-cuspidate. 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, palmate lobes in male only; basis with group of anteroproximal setae; carpus longer than propodus, carpus 1.7 × as long as propodus, 2.3 × as long as broad; propodus 'subtriangular' with well developed posterodistal lobe, anterior margin with 4 groups of robust setae, lateral surface with 12 cuspidate setae in 3 rows, posterolateral margin with 5-6 serrate setae; medial surface with about 13 cuspidate setae; palm transverse with 5 serrate setae along palm, without spine patch on posterodistal corner; dactylus simplidactylate, without anterodistal denticular patch. Gnathopod 2 sexually dimorphic; subchelate; coxal gill lobate; basis slightly expanded; 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, not projecting between merus and propodus; propodus subquadrate, 1.3 × as long as wide; palm acute, reaching 43% along posterior margin, smooth, evenly rounded, lined with robust setae, posterodistal corner with groove, posteromedial surface of propodus with groove; dactylus slightly longer than palm, curved, without anteroproximal bump, posterior margin smooth, minutely spatulate distally; gill lobate. Pereopods 2–4 coxae wider than deep or as wide as deep. Pereopods 3–7 cuspidactylate. Pereopod 3 dactylus without anterodistal patch. 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, dactylus without anterodistal denticular patch. Pereopod 5 propodus distinctly longer than carpus; dactylus with anterodistal denticulate patch. Pereopod 6 coxa posterior lobe inner view posteroventral corner rounded, posterior margin oblique to ventral margin, posterior lobe with ridge, posterior lobe with 4 marginal setae; coxal gill lobate. Pereopod 7 basis lateral sulcus present, slightly pronounced, posterodistal lobe present, shallow, broadly rounded; distal articles (merus and carpus) slender; merus posterior margin evenly rounded.

Pleon. Pleopods all well developed, biramous. Epimeron 2 slightly longer than epimeron 3. Epimeron 3 posterior margin minutely serrate, with minute setae, posteroventral corner subquadrate. Uropod 1 peduncle with about 17–18 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 3 marginal robust setae in 1 row; outer ramus with 5 marginal robust setae. Uropod 2 not sexually dimorphic; peduncle with about 13 robust setae; inner ramus subequal in length to outer ramus, with 5 lateral robust setae and 2 medial robust setae; outer ramus with 2 marginal robust setae in 1 row. Uropod 3 peduncle with 2 to 4 robust setae; ramus not fused to peduncle; ramus shorter than peduncle, 2.3 × as long as broad, linear (narrowing), with 3 marginal robust setae and more than 5 apical setae. Telson as broad as long, apically incised, dorsal midline entire, with marginal and apical robust setae, 10–12 setae per lobe.

Female (sexually dimorphic characters). Based on paratype, female, 7.5 mm, AM P.92566. Antenna 2 peduncular articles slender. Gnathopod 1 parachelate; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; propodus anterior margin with 2 groups of robust setae; palm with spine patch on posterodistal corner. Gnathopod 2 mitten-shaped; palm obtuse, nearly straight, not lined with robust setae, without cuticular patch at corner of palm; dactylus subequal in length to palm. Epimeron 3 posterior margin smooth.

Distribution. Bora Bora, Society Islands.

Remarks. Tongorchestia borabora is similar to T. pangaimotu from Tonga. These species are the same size and look very similar. However, in the male of T. borabora the palm of gnathopod 2 reaches further down the posterior margin of the propodus (43%) than in T. pangaimotu (about 33%, not 25–27% as originally stated), there is a small proximal projection on the posterior margin of dactylus in T. pangaimotu not present in T. borabora , there is a small anterodistal denticulate patch on each of the dactyli of pereopods 5–7 in T. borabora which is absent in T. pangaimotu , the ramus of uropod 3 is not fused to the peduncle in T. borabora (partially fused in T. pangaimotu ) and the ramus is about 2.2 × as long as broad in T. borabora (3.3 × in T. pangaimotu ). In the female of T. borabora there is a distinct posterodistal denticulate patch on the palm of gnathopod 1 which is absent in T. pangaimotu .

These species appear to be closely related sister taxa. It will be interesting to see if additional species of Tongorchestia are living on other Western Pacific oceanic islands and how they are morphologically related to each other.

Figures

FIGURE 1. Tongorchestia borabora sp. nov., holotype, male, 9.7 mm, AM P. 92565, Viatape, Bora Bora, Society Islands. Scale lines for H represent 200 µm; Mp, Mx 1, & Mx 2 represent 100 µm; lMd represent 20 µm; and A 2 last article represent 10 µm.

FIGURE 2. Tongorchestia borabora sp. nov., holotype, male, 9.7 mm, AM P. 92565, female, AM P. 92566, Viatape, Bora Bora, Society Islands. Scale lines for male G 1 represent 200 µm; male G 2 represent 100 µm; female G 1 & G 2 represent 20 µm.

FIGURE 3. Tongorchestia borabora sp. nov., holotype, male, 9.7 mm, AM P. 92565, Viatape, Bora Bora, Society Islands. Scale lines for P 3, P 4, P 5, P 6 & P 7 represent 200 µm.

FIGURE 4. Tongorchestia borabora sp. nov., holotype, male, 9.7 mm, AM P. 92565, Viatape, Bora Bora, Society Islands. Scale lines for EP represent 200 µm; Ur, U 1, U 2, U 3 & T represent 100 µm.

FIGURE 5. Tongorchestia borabora sp. nov., paratype, female, AM P. 92566, Viatape, Bora Bora, Society Islands, showing five groups of scales on the ventroproximal side of the head. Scale lines for H represent 200 µm.