Fissarcturus BATHYWEDDELLENSIS 2007, SP. NOV.

FISSARCTURUS BATHYWEDDELLENSIS SP. NOV.

(FIGS 1–10)

Material examined: holotype, male (9 mm), station ANDEEP 133-3-E, 65°20.17′−20.08′S, 54°14.30′−34′W, 1121 m, north-western Weddell Sea, 7 February 2002, RV Polarstern (ZMH K−40890).

Paratype: female (7.8 mm), station ANDEEP 133-3, station data as holotype (ZMH K-40891); male (9 mm), station ANDEEP 41-3-E, 59°22.24′−22.57′S, 60°04.06′−34′W, 1121 m, off Elephant Island, 26 January 2002, RV Polarstern (ZMH K-40892); 5 manca I stages, station ANDEEP 46-7-E, 60°38.33′−06′S, 53°57.38′−51′W, 3894 m, 30 January 2002, RV Polarstern (ZMH K-40893).

Distribution: South Shetland Islands, Weddell Sea, Southern Ocean.

Etymology: The species name is derived from Latin bathy-, which means ‘deep’ and refers to the depth and location of the type locality in the Weddell Sea. The gender is masculine.

Diagnosis: Dorsal pereonal spination with elements in submedial, dorsolateral, lateral and coxal rows, dorsal spines smooth, anterior ones long, prominent, spines on posterior pereonites and on pleotelson shorter, blunt. Proximal last lateral pair of spines inserted almost at caudal tip, at 98% of the pleotelson length. Minute pleotelsonic apex.

Description of the holotype male: Body length 9 mm (Fig. 1). Eye large, oval. Eye 0.4 of lateral length of head. Preocular spine long, acuminating, blunt, almost as long as supraocular spine. Supraocular spine blunt, long, directed frontally, slightly more than twice as long as diameter of eye. Second cephalic spine broken off in male. Two lateral smaller spines on head in male. Body long, slender (Fig. 1), pereonites 1–4 of about same length, pereonites 1–3 widest. Pereonite 4 about as wide as pereonites 5–7. All pleonites fused with pleotelson. Pereonal spination comprising elements in submedial, dorsolateral, lateral and coxal rows. Submedial and dorsolateral spines present on pereonites 1–4, submedial spines on pereonites 5–7 similar to 1–4, but smaller than on 1–4. Submedial, dorsolateral and lateral spines present on pereonites 1–7, longer and more stout on pereonites 1–4, on pereonite 4 shorter than on 3, blunt, small and tubercularlike on 5–7. Coxa 1 with 3–4 marginal spines (sexually dimorphic). Four contiguous coxal spines present on pereonite 1, frontally directed. One spine on coxae 2– 7 each, longest on pereonites 2 and 3, in male tubercular-like. Ornamentation of coxae of pereonites 1–7 with tubercles, some spine-like. Six major submedial and sublateral spines on pleotelson and 4–5 lateral, last caudolateral one very prominent. Pleotelson length 0.25–0.3 times total body length. Pleotelson width 0.5 total pleotelson length. Position of most posterior lateral spines 98% of pleotelson length. Position of last lateral pair of spines on pleotelson apically. Pleotelson apex minute, convex.

A1 (Fig. 2) first peduncular article broadest and shorter than second, first and second both with medial and lateral feather-like setae, more laterally. Peduncular article 3 0.4 times length of article 2. Antenna 1 flagellum, aesthetascs seven groups of two, terminal simple setae and one short feather-like one.

A2 (Fig. 2) peduncle 0.58 body length, with strong lateral spines on articles 2–4. Peduncular articles 3–5 with lateral and medial short spinules. Antenna 2 flagellum broken off in male.

Mandibles (Fig. 2) without palp, asymmetrical. Pars incisiva of lMd with three teeth.

Mx1 (Fig. 2) of two endites, both slightly narrowing distally, lateral one distally curved medially, apex with 11 strong smooth spines. Medial endite shorter, but lost during dissection.

Mx2 (Fig. 2) consisting of three endites. Outer, lateral, endite with three long setulated setae, medial endite also with three setulated setae, inner endite with two rows of nine shorter setulated setae.

Mxp (Fig. 2) with long-oval epipod, strong endite and a five-segmented palp. Endite distodorsally with four spine-like setulated setae. One coupling hook in male. Third palpal article longest, first and last smallest, dense medial brush of long setae equipped with few setules, especially on third to fifth articles.

P1 (Fig. 3) basis slightly shorter than propodus, carpus trapezoidal, propodus subchelate and slender. Pereopod 1 propodus, length 0.5 times width. Dactylus shorter than propodus, with one long, strong distal claw. Propodus and dactylus densely setose. Ventral surface of propodus with few setae, most on medial part and on palm. Mediodorsal side of propodus forming a concave ‘spoon’, curved dorsolateral surface with long setae, arranged in six parallel transverse rows of combs, dorsal part of palm bearing many medially directed setae.

P2–4 (Fig. 3) similar. P2 shortest, P4 longest, many long setae on posteromedial margins, some long setae on anterolateral margins, especially on carpus and propodus. Dorsal ornamentation of basis with tuberculated spines, and small blunt spines scattered on ventral side of carpus and propodus of P3 and P4, ischium-carpus of P2–P4 dorsal margin with tuberculated spines. Eight, seven, eight setal groups on carpus. Seven, five, four setal groups on propodus. Pereopods 2–3 dactylus, length 0.5 propodus. Unguis as long or longer than dactylus. Pereopods 2–3, unguis, length 1 dactyus. Pereopod 4, dactylus, length 0.5 propodus. Pereopod 4, unguis, length 0.5 dactylus.

P5–7 (Fig. 4) similar in shape and setation and shorter and stouter than P2–P4, P7 smallest. Basis of P5 and P6 longest article, of P7 propodus longest. Basis with 1–2 feather-like setae. Merus, carpus and propodus with ventral strong setulated sensory setae, and some additional ventrolateral ones. Propodus dorsally with one feather-like seta and several simple setae. Dactyli all broken off in holotype.

Plp1 (Fig. 4) sympod 0.4 as long as rami, with seven coupling setae. Exopod length 0.9 length and 1 width of endopod. Male pleopod 1 exopod terminally and medially equipped with setae. Male pleopod 1 endopod, groove opening at 80% of length, and groove opening with row of small scales. Endopod with eight distal and 20 lateral setae.

Plp2 (Fig. 4) very similar to Plp1, but with much shorter sympod, about 0.2 as long as rami, without lateral spines, but with three medial coupling setae. Appendix masculina 1.2 length of endopod, simple.

Plp3 (not illustrated) with very short sympod, as following pleopods; exopod with shorter lateral plumose setae, endopod bare.

Plps 4 and 5 (Fig. 5) exopod with two and one plumose seta, respectively.

Urp (Fig. 5) endopod 0.7 length of exopod. Uropod endopod with three distal setae.

Female paratype (differences to holotype male) of 7.8 mm length: Preocular spines acute (Figs 6, 7). Second cephalic spine, longer and more robust than supraocular spine, acute in female, three other spines on head. Pereonites, pleonites and pleotelson of female with very similar pattern of spination if compared with male, but spines are generally slightly longer and more acute. Four erect coxal spines on pereonite 1. Antennula (Fig. 8) with two pairs of aesthetascs and fewer feather-like setae on lateral and medial margins. Antenna (Fig. 8), fifth article with few tubercles, flagellum of five articles. Maxilliped (Fig. 8) with long, distally acuminating epipod, strong endite and a fivesegmented palp. Endite distodorsally with seven spine-like setulated setae, medially with another three setae, no coupling hooks present. Medial brush of long setae equipped with few setules more dense than in male, especially on third to fifth articles. Pereopods (Figs 9, 10) all very similar, but ischium, merus and carpus of female with distal, blunt, spine-like projections. Endopodite of uropod (Fig. 10) with three setae.

Remarks: F. bathyweddellensis can easily be distinguished from other species of the genus by the spination on the dorsum of the body. It is similar to F. emarginatus Brandt, 1990, but has a longer and stouter second cephalic spine. In addition, its pereonal spination comprises elements in submedial, dorsolateral, lateral and coxal rows, whereas that of F. emarginatus only has submedial, dorsolateral and coxal rows. In contrast to the long and acute spines of F. emarginatus on the posterior pereonites and pleonites, those of F. bathyweddellensis are shorter, blunt and more tubercle-like on these body segments.