Periparatanais mergaxilla Bird 2019, n. sp.
Creators: name: Bird, Graham J.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Tanaidacea
Tanaididae
Periparatanais
Periparatanais mergaxilla

description: 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.
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.
description: Published as part of Bird, Graham J., 2019, Tanaidacea (Crustacea: Peracarida) from the Southern French Polynesia Expedition, 2014. I. Tanaidomorpha, pp. 1-75 in Zootaxa 4548 (1) on pages 35-40, DOI: 10.11646/zootaxa.4548.1.1, http://zenodo.org/record/2584426