Tanaidacea (Crustacea: Peracarida) from the Southern French Polynesia Expedition, 2014. I. Tanaidomorpha Author Bird, Graham J. text Zootaxa 2019 2019-01-22 4548 1 1 75 journal article 28526 10.11646/zootaxa.4548.1.1 d03d8191-e882-4de4-943c-2b9b59d7570a 1175-5326 2584426 4C6DB448-DE0B-41E1-BAB1-4ACAE95F756F Periparatanais mergaxilla n. sp. ( Figs 16–18 ) Diagnosis . Monotypic; see genus diagnosis above. Etymology . Conjunction of Latin merga ‘two-pronged pitchfork’ and axilla ‘armpit’, alluding to the spinose apophysis on the posterior margin of the coxae of pereopods 4–5, as noun in apposition. Material examined . Holotype —non-ov. ♀ , 1.8 mm , P. 102328 , Stn 64-2, Morane, rubble, 19 m , 12 October 2014 , coll. A. Berthelsen, A. Reid, S.J. Keable, and C. Bedford. Paratypes —MORANE: two non-ov. ♀♀ P. 102329 , one non-ov. ♀ dissected on two microslides P.102330.001, Stn 64-2. GAMBIER ISLANDS: one non-ov. ♀ P. 102331 , Stn 66-A; two non-ov. ♀♀ MA73585, Stn 66-4. Description . Holotype non-ovigerous female , 1.8 mm (P. 102328 ). Habitus ( Fig. 16A–B ) slender, 8.9 times ltb (extended, ca . 6.5 times ltb contracted). Cephalothorax ( Fig. 16A–B, D ) 1.3 times ltb, just longer than pereonites 1–2 combined (contracted), with single anterolateral setae posterior to eyes. Pereon with all pereonites shorter than broad, pereonite-1 shortest, pereonites 2–3 and 6 subequal, pereonites 4–5 subequal, longest; pereonite-1 with four anterodorsal setae, other pereonites with two, pereonites 4–6 with two posterolateral setae. Pleon 1.34 times ltb, about 19% of body length (contracted), pleonites equal in length, with slightly raised sternites. Pleotelson ( Fig. 16C ) shorter than pleonites 4–5 combined, with two posterolateral setae, two posterodistal setae and two PSS, two apical setae, and two deflected ventro-apical setae. Paratype non-ovigerous female , 2.2 mm (P.102330.001). Antennule ( Fig. 16E ) 0.9 times length of cephalothorax, 4.3 times ltb; article-1 1.3 times longer than articles 2–3 combined, 2.4 times ltb, with one distomesial seta, lateral margin with group of three PSS , a simple seta and at least two PSS and distal group of one simple seta and three PSS ; article-2 shorter than broad, with lateral and mesial single setae; article-3 five times length of article-2, 4.5 times ltb, with apical spur, without distinct cap-like segment, with five simple setae, one aesthetasc and one PSS . Antenna ( Fig. 16F ) article-1 shorter than broad, naked; article-2 slightly inflated, with ventral ridge, 1.2 times ltb, twice length of article-3, with dorsodistal seta, distolateral seta, and small ventral seta; article-3 just longer than broad, with acute dorsodistal fused spine; article-4 just shorter than article-2, 2.7 times ltb, with one simple seta and three PSS ; article-5 half length of article-4, 2.4 times ltb, with distal seta; article-6 caplike, with one short and four long setae . Mouthparts. Labrum ( Fig. 17A ) distally setulate, hood-like. Mandibles robust, right incisor not observed; left mandible ( Fig. 17B ) distally setulate, incisor weakly crenate, lacinia broad, weakly flared and distally crenate, molar cylindrical with rosette of apical spines. Labium not observed. Maxillule ( Fig. 17C ) with at least eight terminal spines, three of which are larger than others and weakly hooked. Maxilla not observed. Maxillipeds ( Fig. 17D–E ) typical paratanaidin, basis with seta about length of endite. Endites with distomedial tubercles longer than broad, incisor-like, medial seta length of endite. Palp article-1 as long as broad, naked; article-2 lateral seta short, mesial margin with two unequal simple setae, and pectinate seta; article-3 with mesial apophysis bearing three serrulate setae, with one inner (oral) small simple seta; article-4 with proximomesial setules, one small superior seta and five distal serrulate setae. Epignath not observed. Cheliped ( Figs 16D ; 17F–G ) with coxal sclerite extending to posterior margin of cephalothorax ( Fig. 16D ); basis 1.4 times ltb, posterior lobe length of anterior mass, latter with dorsodistal seta; merus typical, with ventrodistal seta; carpus 1.8 times ltb, with two dorsal and two ventral setae. Chela just longer than, but narrower than carpus, propodus 2.1 times ltb, palm 1.9 times longer than fixed finger; palm with two ventrodistal setae, slender spine near articulation with dactylus, and one dorsomesial pectinate spine ( Fig. 17G ); fixed finger with tricuspid incisive margin and three setae, middle longest, terminal spine narrow; dactylus strong, with one flat spine on incisive margin and proximomesial spine. Pereopod-1 ( Fig. 18A ) coxa with seta on slight apophysis; basis arcuate, 3.5 times ltb, with superoproximal seta; ischium with small seta; merus twice length of broad, with two small inferodistal setae; carpus 0.9 times length of merus, 1.8 times ltb, with two superodistal setae and two small inferodistal setae; propodus 1.6 times longer than carpus, 3.4 times ltb, with one superodistal seta and one inferodistal seta; dactylus about one third length of unguis, with accessory seta; unguis together with dactylus 0.8 times length of propodus. Pereopod-2 ( Fig. 18B ) coxa with seta; basis broader than pereopod-1, 2.6 times ltb, with superoproximal seta; ischium with seta; merus short, length of broad, with inferodistal spine and seta (mesial); carpus 1.3 times longer than merus, 1.2 times ltb, with superodistal crotchet, and two unequal inferodistal crotchets; propodus length of merus and carpus combined, 2.3 times ltb, with two unequal superodistal setae and one inferodistal seta; dactylus with accessory seta, 0.4 times length of unguis; unguis together with dactylus about 0.9 times length of propodus. Pereopod-3 ( Fig. 18C ) like pereopod-2 but slightly shorter overall; propodus with one superodistal seta. Pereopod-4 ( Fig. 18D ) coxa broad with posterior apophysis (see genus diagnosis); basis broader than in pereopods 2–3, 1.6 times ltb, with longitudinal groove on superodistal margin, inferior margin with two PSS; ischium with two unequal setae; merus sub-geniculate, longer than broad, with two unequal inferodistal crotchets, and spinulate inferior margin; carpus about length of merus, 1.1 times ltb, distally wider, with superodistal seta, three unequal distal crotchets, inferior margin with paired spinulate ridges; propodus just longer than carpus, 1.9 times ltb, widest at midlength with superior PSS, with superodistal slender spine and two highly unequal inferodistal crotchets; dactylus and unguis claw-like, unguis half length of dactylus, together 0.6 times length of propodus. Pereopod-5 ( Fig. 18E–F ) like pereopod-4 but basis with one inferodistal PSS. Pereopod-6 ( Figure 18G–H ) as pereopods 4–5, including coxa ( Fig. 18H ) but basis naked; propodus without superior PSS and with one thick and two slender superodistal spines. FIGURE 16. Periparatanais mergaxilla n. sp. non-ovigerous female holotype (P.102328). A, habitus, actual; B, habitus, drawn as if pereon contracted; C, pleotelson; D, cephalothorax and pereonite-1, lateral. Non-ovigerous female paratype (P.102330.001). E, antennule; F, antenna; G, uropod. Scale bars: habitus 1 mm, others 0.1 mm. FIGURE 17. Periparatanais mergaxilla non-ovigerous female paratype (P.102330.001). A, labrum; B, left mandible; C, maxillule; D, maxilliped, lateral; E, maxilliped endites; F, right cheliped; G, left chela palm distomesial spine. Scale bars: 0.1 mm. FIGURE 18. Periparatanais mergaxilla non-ovigerous female paratype (P.102330.001). A–E, pereopods 1–5 respectively: F, pereonite-5 coxal spines; G, pereopod-6; H, pereopod-6 coxal spines, inner view; I, pleopod. Scale bars: 0.05 mm, except H 0.025 mm. Pleopod ( Fig. 18I ) peduncle just longer than broad; rami unequal in length and proportion; endopod 2.5 times ltb, with distomesial seta, proximolateral plumose seta separated by gap from fringe of seven distolateral plumose setae, distalmost whip-like; exopod longer and wider than endopod, 2.3 times longer than broad, with proximal plumose seta, and distal fringe of 13 lateral plumose setae. Uropod ( Fig. 16G ) just shorter than pleotelson, peduncle 1.1 times ltb; endopod two-segmented, 1.3 times longer than peduncle, segment-1 about as long as segment-2, with distal seta and two PSS, segment-2 with four setae and one PSS; exopod one-segmented, half length of peduncle, 0.7 times length of endopod segment-1, with subdistal seta and two apical setae. Intraspecific variation . Body length 1.3–2.2 mm (n=6). Distribution and habitat . Taravai (Gambier Islands) and Morane; 10–19 m , from (coral?) rubble. Remarks . This paratanaid is easily distinguished from the other known paratanaidin from French Polynesia (see below) by its antennule configuration and the spinose coxa of pereopods 4–6.