Pseudotanais (Pseudotanais) artoo Blazewicz-Paszkowycz & Stepien, sp. nov.

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.