Pseudotanais (Pseudotanais) artoo Błażewicz-Paszkowycz & Stępień, 2015

Jakiel, Aleksandra, Stępień, Anna, Jóźwiak, Piotr, Serigstad, Bjørn & Błażewicz-Paszkowycz, Magdalena, 2015, First record of Tanaidacea (Crustacea) from a deep-sea coral reef in the Gulf of Guinea, Zootaxa 3995 (1), pp. 203-228 : 221-224

Pseudotanais (Pseudotanais) artoo Błażewicz-Paszkowycz & Stępień sp. nov.

Figs 13–15

Material examined. Holotype— non-ovigerous female, length 1.1 mm (Cat. No. ZMBN 105692), Sta I BR, Gulf of Guinea, 4°45'40.7"N 3°09'10.8"W, depth 386 m, 17 November 2012.

Paratype— One female (dissected, length 2.0 mm) (Cat. No. ZMBN 105693); locality the same as holotype.

Diagnosis. Eyes absent. Pereonites 4–5 not longer than pereonites 1–3 combined. Antennule article-1 slender, six times as long as wide. Antenna articles 2–3 with distal simple setae. Molar of left mandible slender and acuminate. Article-2 of maxilliped palp with ventral spine. Cheliped carpus elongated, about 2.4 times as long as wide. Chela forcipate. Females with pleopods. Uropod exopod bisegmented, as long as half of endopod segment-1.

Etymology. The name is given for the company Artoo Marine Biology Consultants LLP founded by Roger Bamber and Roni Robbins, and which provided consultancy expertise for a long time off the coast of West Africa.

Description of female. Body ( Fig. 13 A–B) 3.6 times as long as wide, length 2 mm (holotype 1.1 mm). Cephalothorax trapezoidal, 1.3 times as long as wide, longer than any pereonite, naked; eyes absent. Pereonite-1 shortest, pereonite-2 twice as long as pereonite-1, pereonites 3 and 6 subequal, 1.4 times as long as pereonite-2, pereonite-4 3.6 times as long as pereonite-1, pereonite-5 longest, four times as long as pereonite-1 (all pereonites respectively 9.4, 4.8, 3.6, 2.5, 2.4, 3.5 times as wide as long). Pleonites narrower posteriorly, all pleonites subequal, Antennule ( Fig. 14 A) article-1 six times as long as wide, with midlength seta, two outer distal simple setae and inner distal seta as long as articles 2 and 3 combined; article-2 0.4 times as long as article-1, with inner distal seta; article-3 just shorter than article-2, with one simple and six distally trifurcate setae and aesthetasc.

Antenna ( Fig. 14 B) article-1 fused with body (not illustrated); article-2 1.4 times as long as wide, with fine outer distal seta; article-3 1.2 times as long as article-2, nearly twice as long as wide, with fine outer distal seta; article-4 5.3 times as long as wide, with four simple distal setae; article-5 half as long as article-4, with simple seta; article-6 minute, with four distal setae and aesthetasc.

Mouthparts. Right mandible ( Fig. 14 C) with serrated incisor, well developed. Left mandible ( Fig. 14 D) with blunt incisor, lacinia mobilis typical for the genus, molar slender, pointed. Maxillule endite ( Fig. 14 E) tipped by five thin setae; palp ( Fig. 14 F) with distal seta. Labium ( Fig. 14 G) naked with medial cleft.

Maxilliped ( Fig. 14 H, H’) endites fused, naked, each with shallow tubercle. Palp article-1 naked; article-2 with distomedial spine and inner seta; article-3 with five long and two short setae along inner margin; article-4 with five simple distal setae and subdistal seta on outer margin.

Epignath ( Fig. 14 I) naked, linguiform.

Cheliped ( Fig. 15 A) merus subtriangular, with single midventral seta; carpus 2.4 times as long as wide, with two midventral setae; chela forcipate, propodus as long as wide and 0.8 times as long as fixed finger, with ventral seta and seta near dactylus insertion; fixed finger cutting edge with three (one broken) setae; unguis and dactylus slender.

Pereopod-1 ( Fig. 15 B) slender; basis 5.5 times as long as wide, with seta proximally; ischium with simple seta; merus 0.25 times as long as basis with seta distally; carpus 1.5 times as long as merus, with simple seta distally; propodus 1.5 times as long as carpus, with two simple setae distally; unguis and dactylus combined 0.7 times as long as propodus.

Pereopod-2 ( Fig. 15 C) basis 5.3 times as long as wide, with penicillate seta on dorsal margin; ischium with simple seta; merus little longer than carpus, with seta and short spine distally, microtrichia present; carpus with ventrodistal blade-like seta half as long as propodus, simple seta and microtrichia on ventral margin, and simple seta dorsally; propodus 1.4 times as long as carpus, with ventrodistal spine and two setae dorsodistally, ventral margin covered with microtrichia; dactylus little longer than unguis.

Pereopod-3 ( Fig. 15 D) similar to pereopod-2, but basis with two penicillate setae at midlength on both margins, merus wider than in pereopod-2, without microtrichia.

Pereopod-4 ( Fig. 15 E) basis 3.3 times as long as wide, with dorsal penicillate seta, ischium naked, merus with seta, carpus with blade-like spine broken and with only simple seta, propodus similar to pereopod-5, with spine and two long simple setae distally.

Pereopod-5 ( Fig. 15 F) basis 3.4 times as long as wide, with two midventral penicillate setae and penicillate seta dorsally; ischium with ventral seta; merus naked; carpus about twice as long as merus, with blade-like seta on ventral margin and simple seta dorsodistally; propodus just longer than carpus, with simple ventrodistal seta and dorsodistal seta longer than dactylus and unguis combined.

Pereopod-6 ( Fig. 15 G) basis 5.8 times as long as wide, with ventrodistal seta; ischium naked; merus 0.2 times as long as basis, naked; carpus twice as long as merus, with three simple setae distally; propodus 0.8 times as long as carpus, with three simple setae distally; dactylus 0.5 times as long as propodus.

Pleopod ( Fig. 15 H) endopod with four distal setae; exopod with eight distal setae.

Uropod ( Fig. 15 I) basis naked, exopod half as long as endopod, segment-1 with simple seta and segment-2 with robust terminal seta; endopod bisegmented (segments fussed) with at least one subterminal seta.

Distribution. The species is known only from type locality at a depth of 386 m.

Remarks. The blind Pseudotanais artoo sp. nov. with a ‘forcipate’ chela belongs to the ‘ forcipatus ’ group defined by Bird & Holdich (1989). The new species can be distinguished from the other blind members of this group by a combination of characters. The presence of pleopods in females separates it from P. (P.) forcipatus ( Lilljeborg, 1864) and P. (P.) s oj a Błażewicz-Paszkowycz, Bamber & Jóźwiak, 2013 and the uropodal exopod is only half as long as the endopod, which is more than three quarters as long in P.(P.) falcicula Bird & Holdich, 1989 , P. (P.) mexikolpos Sieg & Heard, 1988 , P. inflatus Kudinova-Pasternak, 1973 , P. (P.) v i t j a z i Kudinova-Pasternak, 1966, and P. (P.) vulsella Bird & Holdich, 1989 . The cheliped carpus (2.5 times as long as wide) is more slender than in P. (P.) californiensis Dojiri & Sieg, 1997 and in P. soja (ca. 1.5 times longer than wide).

Overall, P. artoo appears to be most similar to P. (P.) abyssi Hansen, 1913 but has a much more robust bladelike seta on the carpus of pereopods 2–3. In addition, the exopod of the uropod of P. (P.) abyssi is almost two-thirds as long as the endopod. Rather than a key to distinguish the species of the ‘ forcipatus -group’, Table 1 summarises their principal morphological differences.

Figures

FIGURE 13. Pseudotanais (Pseudotanais) artoo sp. nov., holotype female. A, body lateral view; B, body dorsal view. Scale bar: 0.5 mm.

FIGURE 14. Pseudotanais (Pseudotanais) artoo sp. nov., female. A, antennule; B, antenna; C, right mandible; D, left mandible; E, maxillule, endite; F, maxillule, palp; G, labium; H, maxilliped endite; H’, maxilliped palp; I, epignath. Scale bar: a = 0.1 mm for A – B; b = 0.1 mm for C – I.

FIGURE 15. Pseudotanais (Pseudotanais) artoo sp. nov., female. A, cheliped; B, pereopod- 1; C, pereopod- 2; D, pereopod- 3; E, pereopod- 4; F, pereopod- 5; G, pereopod- 6; H, pleopod; I, uropod. Scale bars: 0.1 mm.