Paragathotanais vikingus Bird, 2010, sp. nov.

Paragathotanais vikingus sp. nov.

Figs 3–6

Diagnosis. Paragathotanais with cephalothorax longer than pereonites 1–2 combined; pereonites all shorter than long, with lateral crenulations; antenna article-2 without spinules; pereopods 4–6 dactylus with two equal distal spines; uropod with slight exopod process.

Material examined. Holotype: neuter (non-ovigerous female?), BIOICE Stn 2849, Iceland Basin, IMNH.3307. Allotype: male, BIOICE Stn 3069, Iceland Basin, IMNH.3311. Paratypes: One preparatory male, two neuters/non-ovigerous females BIOFAR Stn 264; one neuter, BIOICE Stn 2332, IMNH.3309; one neuter, BIOICE Stn 2849, IMNH.3307; one neuter (dissected on microslide, IMNH.3967), one male (IMNH.3304), BIOICE Stn 3069; two neuters, one male, BIOICE Stn 3280, IMNH.3308; one neuter, BIOICE Stn 3539, IMNH.3305; one neuter, BIOICE Stn 3543, IMNH.3310; two neuters, one early preparatory male, BIOFAR Stn 264. See Appendix A for details of these stations.

Description. Neuter (non-ovigerous female). Cuticle shiny. Body (Fig. 3 A) slender or fairly slender, 6.7–7.4 times as long as broad; overall length 1.63–2.20 mm (or 1.46–2.05 mm fully contracted). Cephalothorax (Fig. 4 A) elongate, 1.6–1.8 times longer than broad (mean =1.65, n = 8) and longer than pereonites 1–2; sclerites proximal to chelipeds fused ventrally (but with faint internal suture) with narrow gap and acute anterior process. Pereonites 1– 6 0.56, 0.83, 0.83, 0.80, 0.75 and 0.53 times as long as broad respectively; pereonites 1-5 with finely crenulate lateral margins. Pleon longer than pereonite-6; pleonite-5 with lateral simple seta. Pleotelson (Fig. 3 B) as long as three preceding pleonites, conical in dorsal view, with deflexed acuminate process.

Antennule (Fig. 3 C) 0.6 times as long as cephalothorax; article-1 about half of total length; setation as figured. Antenna (Fig. 3 D) article-2 larger than article-3, both without setae or spinules; other setation as figured.

Labrum (Fig. 4 B) conical, distally setose. Labium not recovered. Mandibles (Fig. 4 C-D) small with reflexed molar process blunt-tipped; left mandible with bifid incisor process and small lacinia mobilis. Maxillule (Fig. 4 E) endite very slender, with ten unequal terminal spines. Maxilliped (Fig. 4 F) bases with distinct ‘waist’ and small seta near each palp attachment; endites with two setae and weakly sculpted distal margin; palps typical of genus.

Cheliped (Fig. 4 G) typical of genus; basis about as long as broad; merus subtriangular with one ventral seta; carpus 1.7 times as long as broad, with two ventral setae and two dorsal setae (proximal and distal); propodus as long as carpus, palm with two unequal medial spines; fixed finger with one ventral seta, three blunt-tipped outer setae, and three low teeth on incisive margin; dactylus and terminal spine thick, with one medial seta.

Pereopod-1 (Fig. 5 A) coxa with seta; basis longer than next three articles; ischium with seta; merus with spine and seta; carpus subrectangular, as long as merus, with three spines; propodus slender, 4.5 times as long as broad and longer than carpus, with two distal spines; dactylus and unguis 0.7 times as long as propodus, dactylus with proximal seta and unguis with spatulate tip (spinning pore?).

Pereopods 2-3 (Figs 5 B–C) similar to pereopod-1 but propodus progressively shorter, with only one distal spine; pereopod-3 basis with pinnate seta.

Pereopod-4 (Fig. 5 D) coxa small; basis distally wider than that of pereopods 1-3, with one pinnate seta; ischium with two unequal setae; merus shorter and more bent than that of pereopods 1–3, with two spines; carpus longer than merus, subrectangular, 2.9 times as long as broad, with three pectinate spines and one seta; propodus about as long as carpus, with one dorsal and two ventro-distal spines; dactylus and unguis together as long as propodus, dactylus grooved, with spinules on inferior margins, with two longer distal spines; unguis shorter than dactylus.

Pereopods 5-6 (Fig. 5 E–G) similar to pereopod-4 but basis with two pinnate setae, pereopod-6 with additional dorso-distal propodal spine.

Pleopods absent.

Uropod (Fig. 4 H) very stout, not projecting out from pleotelson; exopod slight; setation as figured.

Preparatory male. Essentially similar to neuter but with pleopods lacking terminal setae; overall length 1.6 mm.

Male. Body (Fig. 3 E) essentially similar to neuter, but pereonites proportionately slightly shorter, antennule thicker and pleopods (Fig. 3 F) present, in tent-like configuration, with short terminal setae. Overall length 1.6–1.86 mm (1.56–1.74 mm contracted).

Type locality. Bathyal zone of northern Iceland Basin.

Etymology. Latin vikingus alludes to the historical predominance of Viking settlement, culture and trade in the region from where this new species has been recorded.

Distribution records from the AFEN, BIOFAR & BIOICE surveys. So far, in spite of the extensive sampling effort between the Reykjanes Ridge to the southern Bay of Biscay, this species has been recorded in only a very few samples (Fig.6) from the bathyal zone of the Iceland Basin (n = 5) and southern flank of the Iceland- Faroes Rise (n = 1), at 550–1693 m and in mean benthic temperatures of 3–5o C (mode 4o C).

Remarks. The elongate carapace distinguishes P. vikingus from other agathotanaids in this region of the North Atlantic, although Paranarthrura borealis could be confused with it at first sight. P. vikingus is very similar to P. macrocephalus Kudinova-Pasternak, 1986 from the Indian Ocean and P. spinosus Larsen, 2005 from the Gulf of Mexico, but the former’s cheliped basis and carpus are more equal in proportion, its antenna article-2 bears setae and the uropod exopod is more developed. Among other differences, P. s p i n o s u s has a somewhat shorter cephalothorax, longer pereonites 3–6 (without lateral crenulations), longer pereopod spines and one long distal spine on the dactylus of pereopods 4–6.