Paranarthrurella voeringi G.O. Sars 1877

Paranarthrurella voeringi (G.O. Sars, 1877)

(Figures 1–5)

Tanais voringi: G.O. Sars, 1877: 2, 347–370.

Cryptocope voringii: G.O. Sars, 1882: 7, 50–51; G.O.Sars, 1885: 6, 74–78, pl. VII; Hansen, 1913: 3, 109–110, pl. X. Strongyrula arctophylax: Norman & Stebbing, 1886: 12, 110, 116–117, pl. 24 Fig. III. Cryptocope arctophylax: Hansen, 1913: 3, 106, 110–113, pl. 11 Fig. 2 a–k. Leptognathia arctophylax: Sieg, 1983: 317, Lang,1971b: 403.

Tanais voeringi: Sieg, 1980: 537, 11–12.

Leptognathia voeringi: Sieg, 1983: 356.

Biarticulata voeringi: Larsen & Shimomura, 2007: 19.

Material examined: Cryptocope voringii lectotype female, ((NHMO F1691a), sta. 31, 124, 240, 63°10.2' N, 4°59.6' E, depth 760 m; paralectotypes: two males, ((NHMO F1691b), sta. 31, 124, 240, 63°10.2' N, 4°59.6' E, depth 760 m; Strongylura arctophylax, type, (NHM 1903.5.20.8), 56°24'N, 11°19'W (between Ireland and Rockall) 2524 m.

Additional material: four females, PS72/137–5, sta. HG I, 79°7.75' N, 6°7.46' E, depth 1237 m; ten females and one male, PS66/103–1, sta. HGI, 79° 8.97' N, 5° 56.35' E, depth 1300 m.

Diagnosis female: body robust, 5.2 times as long as wide; antennule article 1 little longer than article 4; mandibular molar with a few (seven or less) flat setae terminally; cheliped carpus as long as wide; pleonites 2, 3 and 4 with hyposphenia. Male: swimming type; antennule with seven articles; articles 4–6 with numerous aesthetascs; mouthparts reduced; maxilliped as in females, but endites three times as long as wide, setae on palp articles 2–4 much longer than in female; cheliped and pereopods similar to female, inner side of palm with 17 setae; pleopod rami elongated with setulated setae distally; uropod endopod with three, exopod with two articles.

Description of female: Body (Figs 1 A, B) 5.0 mm long; 5.2 times as long as wide. Carapace 17% of body length, narrowing proximally. Pereonites rounded; pereonite 1 0.4 times as long as wide; pereonite 2 little longer, equal in length to pereonites 3 and 6; pereonites 4 and 5 little longer than pereonite 2; pleon 23% of body length, pleonites 1–5 equal, pleonites 2, 3, and 4 with ventral hyposphenia (Figs 1 C, D); pleotelson wider than pleonites, 0.3 times as long as wide, with few simple setae distally.

Antennule (Fig. 2 A): 5-articled. Article 1 two times as long as wide, with one distal seta on inner margin and one simple and seven bipinnate setae on outer margin. Article 2 over 0.4 times as long as article 1, with two simple and two bipinnate setae distally. Article 3 about half as long as article 2, with one simple and one bipinnate seta distally. Article 4 three times as long as article 3, terminated by one simple and one bippinate seta. Article 5 vestigial, with five setae.

Antenna (Fig. 2 B): 6-articled; article 1 short, wider than long. Article 2 and article 3 each with simple distal seta. First three articles with microtrichia. Article 4 longest almost twice as long as article 5, with three simple and five bipinnate setae distally. Article 5 two times as long as article 4, with one serrated seta. Last article very short, with two short, simple and three serrated setae terminally.

Mouthparts: Labrum (Fig. 2 C) long with numerous short setae distally. Mandibles (Figs 2 D-E) with proximal inner margin covered by numerous minute setae; molar process short, broad and rounded, distally with six or seven short, massive setae (broken on Fig. 2 D); lacinia mobilis well-developed, as long as incisor, strongly crenulated; incisor of left mandible with dorsal row of small denticles. Maxillule (Fig. 2 F) with eleven strong spines terminally; outer margin with simple setae; inner margin with rows of minute setae; palp with two setulated setae. Labium (Fig. 2 G) bilobed; inner lobe with numerous, short setae along distal and outer margin, inner surface strongly crenulated and calcified; outer lobe, vestigial, each with small tubercle. Maxilliped (Fig. 2 H) bases with minute seta distally; endites distally with two simple and two short, flat setae, numerous minute setae on disto-inner margin; palp article 1 naked; article 2 with simple seta on outer margin and long simple and two short setulated setae on inner margin; article 3 with four setulated setae on inner margin and some microtrichia; article 4 with one outer, simple seta, rows of minute setae on inner margin and four setulated setae terminally.

Cheliped (Fig. 3 A): basis wide, naked; merus 0.7 times as long as carpus, with one simple seta ventrally; carpus 1.3 times as long as propodus, with two simple setae on dorsal and ventral margins. Propodus with row of eleven simple setae on inner surface near dactylus insertion and with numerous minute spines; fixed finger with strong claw, two simple setae ventrally; inner margin with teeth and 3 simple setae (Fig. 3 A’). Dactylus with simple seta in middle.

Pereopod 1 (Fig. 3 B): coxa with seta; basis 6.5 times as long as wide, about 4.3 times as long as merus, naked; ischium with simple seta ventrally; merus 0.5 times as long as carpus, with two simple setae on distoventral margin; carpus subequal in length to propodus, with five simple setae subdistally; propodus as long as combined length of dactylus and unguis, with three simple setae on distal margin and one long seta on inner face; unguis 1.7 times as long as dactylus.

Pereopod 2 (Fig. 3 C): similar to pereopod 1, but basis with two bipinnate setae dorsally, carpus with three serrated setae distally and propodus with row of short, simple setae distally.

Pereopod 3 (Fig. 3 D): similar to pereopod 1, but carpus with four serrated setae distally and propodus with row of short, simple setae distally.

Pereopod 4 (Fig. 3 E): basis 3.6 times as long as merus, with two bipinnate setae ventrally; ischium with two simple setae distoventrally; merus 0.7 times as long as carpus, with two serrated setae on distoventral margin; carpus 0.7 times as long as propodus, with four serrated and one simple setae distally; propodus more slender than carpus, with bipinnate seta and two spines dorsally, three serrated and two short setae; dactylus little longer than unguis; both as long as carpus.

Pereopod 5 (Fig. 3 F): similar to pereopod 4, but basis with additional bipinnate seta on dorsal margin; merus (Fig. 3 F’) with doubly-serrated seta and some microtrichia; propodus (Fig. 3 F’’) with doubly-serrated seta and spine on dorsodistal margin.

Pereopod 6 (Fig. 3 G): similar to pereopod 4, but basis naked; propodus with five serrated setae distally and with some microtrichia.

Pleopod (Fig. 3 H): basal article about 1.5 times as long as wide; both endopod and exopod with only rudimentary setation (3 short setae terminally).

Uropod (Fig. 3 I): basal article about as long as wide. Exopod 2-articled; article 1 with one simple seta, article 2 with two simple setae terminally. Endopod 2-articled; article 1 as long as exopod with 2 bippinate setae, article 2 with five simple and two bipinnate setae terminally.

Description of male: Body (Figs 4 A, B) 4.1 mm long; 6.2 times as long as wide. Carapace about 22% of total body length, tapering distally. Pereonites wider than long, width: length ratios are 2.4, 2.3, 2.4, 1.9, 1.4, 2.0 respectively. Pleon relatively long, 35% of total body length; pleonites equal, 2.2 times as wide as long; pleotelson almost 1.2 times as wide as long, terminating in long and narrow apex; apex bears two simple distal setae.

Antennule (Fig. 5 A): 7-articled, about 1.5 as long as carapace. Article 1 with two simple and seven bipinnate setae distally and subdistally. Article 2 1.2 times as wide as long with two simple (one long) and three bipinnate setae distally. Article 3 0.4 as long as article 2, with two simple and one bipinnate setae. Articles 4–6 width: length ratios are 2.3, 1.0 and 0.4 respectively; all with dense row of long, simple setae distally. Last article 4.8 times as long as wide, with one bipinnate and six simple setae terminally.

Maxilliped (Fig. 5 B) bases about as long as wide, with simple, short seta distally. Endites narrow and elongated, three times as long as wide, with two simple and two flat setae terminally. Palp article 1 naked; article 2, with three simple setae on inner margin; article 3 with four setae distoventrally; last article terminated by one short and five long, simple setae.

Cheliped (Fig. 5 C): basis with wide sclerite, bearing one simple subdistal seta. Merus triangular, with one ventral seta. Carpus tapering distally, about 1.5 times as long as wide, with two inner and one outer setae; distally with small tubercle. Propodus about as long as wide, with seventeen simple setae (increasing in length) near dactylus insertion. Fixed finger with two setae ventrally and three on inner margin; inner margin well calcified. Dactylus with one simple seta proximally and process on inner margin near unguis insertion; unguis over one third as long as dactylus.

Pereopods 1–6 similar to those of female.

Pleopod (Fig. 5 D): basal article about 1.5 times as long as wide, naked. Both rami elongate, equal in length. Endopod with thirteen setulated setae (outer setae shorter), proximal seta separated from remainder by gap. Exopod terminating in sixteen setulated setae.

Uropod (Fig. 5 E): basal article naked. Endopod 3-articled; article 1 with seven bipinnate setae; article 2 with two bipinnate setae; article 3 with five simple and two bipinnate terminal setae. Exopod 2-articled, about 0.6 times as long as endopod; article 1 with distal, simple seta; article 2 little longer than article 1, with two simple terminal setae (one long).

Distribution: The recently collected material is from the Fram Strait (north west of the Svalbard Archipelago) from a depth of 1300 m. Previously the species was known from west of Norway from a depth range 630 to 1825 m.

Remarks: Of the three species now classified in the genus, Paranarthrurella voeringi is distinguished by its relatively short body, about 5.2 as long as wide, and the well developed hyposphenia on pleonites 2–4. In P. dissimilis and P. caudata the length:width body ratio equals 9.5 and 6.2 respectively while hyposphenia are absent. The first article of the antennule of P. voeringi is relatively short (length:width ratio is 1.6) and it is little longer than the length of the fourth article. The length to width ratio of this article in P. caudata and P. dissimilis is 2.8 and 3.4 respectively. Moreover, P. v o e r i n g i has seven simple, flat setae on the mandible molar and eleven simple setae on the inner surface of the cheliped propodus, while in P. dissimilis the molar has eleven short, flat setae and the propodus of the cheliped has only eight setulated setae.