Coulmannia rossensis, Choudhury, Madhumita, Doti, Brenda L. & Brandt, Angelika, 2011

Choudhury, Madhumita, Doti, Brenda L. & Brandt, Angelika, 2011, Coulmannia rossensis sp. n. (Isopoda, Asellota, Paramunnidae) from the Ross Sea, Southern Ocean, ZooKeys 82, pp. 45-57 : 47-51

Coulmannia rossensis sp. n. Figs 14

Material examined.

Ross Sea, RV Italica.

Holotype: Adult male 1.7 mm (ZMH 42000-718); station H out 2, 72°17.5'S, 170°29.4'E, 353 m depth, 11 Feb 2004.

Paratypes, same locality as holotype: 5 males (1.3-1.4 mm), 4 brooding females (1.6-1.7 mm), 2 females (1.2, 1.3 mm) and 2 juveniles (0.9, 1 mm); (ZMH 42000-719).

Additional material: Station H in 3, 72°17.0'S, 170°13.1'E, 316 m depth, 16 Feb 2004: 5 males, 2 brooding females, 1 female and 2 juveniles. Station H in 4, 72°17.1'S, 170°14.0'E, 196 m depth, 16 Feb 2004: 7 males, 3 females and 2 juveniles. Station H in 2, 72°16.9'S, 170°12.2'E, 391 m depth, 10 Feb 2004: 4 males and 1 female. Station SMN, 74°43.2'S, 164°13.1'E, 366 m depth, 20 Feb 2004: 2 males and 2 juveniles. Station H out 1, 72°15.7'S, 170°24.8'E, 458 m depth, 9 Feb 2004: 2 males, 1 female and 2 juveniles. Station H out 4, 72°18.5'S, 170°26.8'E, 235 m depth, 12 Feb 2004: 4 males and 2 females. Station A 4, 71°18.4'S, 170°28.9'E, 230 m depth, 14 Feb 2004: 1 female. Station C 1, 73°24.5'S, 170°23.2'E, 474 m depth, 18 Feb 2004: 1 brooding female. Station C 2, 73°22.7'S, 170°06.9'E, 410 m depth, 18 Feb 2004: 2 males, 3 brooding females, 6 females and 3 juveniles.

Diagnosis.

Males with dorsal sculpture formed by a pair of granulate humps on pereonites 1-6, and a single granulate hump on pereonite 7 and free pleonite. Females with single granulate hump on all pereonites and free pleonite; hump on pereonite 1 widest and shallowest, following humps gradually becoming narrower and higher towards distal end. Lateral margins of pereonites 1 and 5-7 rounded, those of pereonites 2-4 produced into single process. Coxae rounded, visible dorsally on pereonites 5-7 only.

Description of adult male

(body description based on the holotype male, description of appendages based on a paratype male).Body (Fig. 1a, b) total length 1.7 mm; width 0.6 length, widest at pereonite 3. Cephalon width 1.9 length (Fig. 1c), anterior margin broadly rounded. Eyestalks prominent, width 0.6 length, with 5 ommatidia. Pereonites 1-6 with two granulate humps mid-dorsally, pereonite 7 and free pleonite with a single granulate hump each. Lateral margins of pereonites 1 and 5-7 rounded, those of pereonites 2-4 produced into a single process. Coxae rounded, visible in dorsal view on pereonites 5-7 only. Pleotelson and free pleonite together 1.7 as long as last 3 pereonites combined. Pleotelson oval, lateral margins smooth and convex, apex pointed. Uropods inserted at about 2/3 of pleotelson length in posterolateral indentations.

Antennula (Fig. 2a), articles 1-3 longer than wide; first article not extending beyond apex of eyestalk, with 1 penicillate and 4 simple setae; second article largest, with 4 penicillate and 5 simple setae; article 3 shorter than article 2, with 1 simple seta; article 4 shortest, with 1 penicillate seta, article 5 slightly longer than article 6, without setation; article 6 with 5 simple setae, 1 penicillate seta and 1 aesthetasc.

Antenna (Fig. 2b), article 1 broken off during dissection, without setation (see Fig. 1c); article 2 with 1 simple seta; article 3 shorter than article 5, with 5 simple setae; article 4 shortest, with 2 simple setae; article 5 with 3 simple setae; article 6 longest, with 5 penicillate and 5 simple setae; flagellum with 7 articles, each article with numerous simple setae.

Left mandible (Fig. 2c) stout, without palp; incisor process with 5 blunt cusps; spine row with 1 serrate and 2 simple setae; lacina mobilis 4-cusped; molar process cylindrical, transversely truncated, with lower margin of apex toothed. Right mandible (Fig. 2d) as left one, except for: spine row with 3 serrate and 1 simple setae; lacinia mobilis absent.

Maxillula (Fig. 2e), lateral lobe with 10 stout cuspidate setae distally and 1 simple seta near distal margin; medial lobe with 2 simple and 2 setulate setae distally.

Maxilla (Fig. 2f), lateral and medial lobes with 2 simple and 2 pectinate setae, distomedial margin with single acute projection finely setose; inner lobe with 5 simple, 2 pectinate and 2 setulate setae on distomedial margin, 4 simple slender setae on medial margin.

Maxilliped (Fig. 2g), endite reaching half-length of palp article 3, with 2 coupling hooks, distal margin with 4 setulate setae (see detail), ventral surface with 1 setulate and 2 fan setae, dorsal with 3 setulate setae; epipod ovate, width 0.5 length, reaching dorsal margin of palp article 2. Palp, article 1 with 1 tooth on lateral margin, relative lengths of articles 1.0:1.4:1.4:1.7:1.0.

Pereopod I (Fig. 3a) stoutest. Basis longest article, with 4 simple setae. Ischium with 4 simple setae. Merus with 1 robust and 1 simple setae distodorsally, ventral margin with 4 simple setae. Carpus triangular, length 0.88 ischium length, ventral margin with 2 robust and 4 simple setae and 2 cuticular combs, distodorsal margin with 1 simple seta. Propodus oval, ventral and dorsal margins with 4 simple setae each, anterior surface with 1 simple seta and cuticular combs. Dactylus with 4 simple setae near distal margin and 2 simple setae between unguis and ventral claw, unguis slightly longer than dactylus, ventral claw shorter than unguis, approximately 0.5 unguis length.

Pereopods II–VII (Figs 3 b–f, 4a) subequal in shape and length. Meri distodorsally with 1 robust seta on pereopods II–IV and 2 robust setae on pereopods V–VII; distoventrally with 1 robust seta on pereopods III–VI and 2 robust setae on pereopod VII. Carpi and propodi with 1 distodorsal penicillate seta each; ventral margin with 4 robust setae and 3 robust setae, respectively. Ungues 1.6-1.9 dactyli length, ventral claws 0.35 ungues length.

Pleopod I (Fig. 4b, c), lateral lobes at level of 2/3 of its length, each lobe with 8 simple setae; ventral surface with 8 simple setae; distal margin with 8 simple setae.

Pleopod II (Fig. 4d), sympod lateral margin rounded and setose; endopod stylet-like, curved to the apex of the sympod, relative lengths endopod: sympod, 1.0:1.3; exopod distally concave, without setae.

Pleopod III (Fig. 4e), endopod width 0.6 length, with 3 plumose setae distally; exopod with 2 articles, distal one with 1 simple seta apically, extending beyond tips of endopod setae.

Pleopod IV (Fig. 4f), endopod width 0.54 length, exopod reaching half length of endopod.

Pleopod V (Fig. 4g) width 0.5 length.

Uropod (Fig. 4h) biramous; exopod 0.4 endopod length, distally with 2 simple setae (broken in the specimen drawn); endopod with 5 penicillate and 3 simple setae.

Description of adult female

(Figs 1d, e; 4i). As male in body shape, except for: dorsal sculpture with a single granulate hump on all pereonites and free pleonite; hump on pereonite 1 widest and shallowest, following humps gradually becoming narrower and higher towards distal end. Operculum width 0.74 length, margins finely setose, ventral surface with 6 simple setae. Remaining appendages as those of the male.

Distribution.

Only known from type locality (Fig. 5).

Etymology.

The species name refers to the type locality, the Ross Sea.

Remarks.

Because of the dorsal ornamentation and the lateral margins of the pereonites Coulmannia rossensis sp. n. is most similar to Coulmannia ramosae Castelló, 2004. The main differences between these two species are (characters found in Coulmannia ramosae in parentheses): two granulate humps on pereonites 1-6, single granulate hump on pereonite 7 and free pleonite (two granulate humps on pereonites 1 and 2, single granulate humps on remaining segments); pleotelson width 0.76 length (width 0.51 length, apex of pleotelson more produced); basis of pereopods with simple setae only (with simple and robust setae); propodi of pereopods II–IV with 3 robust setae (with 4 robust setae).