Macrostylis setulosa Mezhov, 1992

Riehl, Torben & Brandt, Angelika, 2013, Southern Ocean Macrostylidae reviewed with a key to the species and new descriptions from Maud Rise, Zootaxa 3692 (1), pp. 160-203: 191-193

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Macrostylis setulosa Mezhov, 1992


Macrostylis setulosa Mezhov, 1992 8 C 216677 -AD 60 - 4 F 8 B-B 55 B- 34627 ABB 7479 Macrostylis setulosa Mezhov, 1992  ; pp. 83–87, Fig. 1 View Figure .

Type fixation. Holotype: non-ovigerous female, 3.2 mm, Mc- 1274, by original designation.

Type material. Holotype: non-ovigerous female, Mc- 1274, with 3 stage III mancae; paratype: non-ovigerous female, 2.8 mm, Mc- 1275. All material deposited at the Zoological Museum of the Moscow State University.

Type locality. Southern Ocean, Scotia Arc, South Sandwich Islands with R/V Akademik Kurchatov, cruise 11, station 880, 57° 07.4’ S, 26 ° 40 ’ W; 757 m depth; by means of the bottom sampler "Okean".

Type material - Remarks. The paratype material collected at stations R/V Akademik Kurchatov 927 originate from a very different locality and depth. Type material was not available for comparison but there is a possibility that they are different species. Because of that, the information given by Mezhov about male characters were excluded here and corresponding stations are listed below as further records instead of type locality. The type locality is hence restricted to the locality of the holotype.

Further records. R/V Akademik Kurchatov, cruise 11, station 927, 56° 08.4’ S, 52 ° 40 ’ W; 1,660 m depth.

R/V Dm. Mendeleev, cruise 43, station 4084 -I, 70 ° 40.6 ’ S, 15 ° 47.8 ’ W; 4,335 m depth.

R/V Dm. Mendeleev, cruise 43, station 4084 -II, 70 ° 53.17 ’ S, 15 ° 04.51’ W; 2,925 m depth.

R/V Dm. Mendeleev, cruise 43, station 4085, 60° 33.35 ’S, 35 ° 37.1 ’ W; 2,705 m depth.

Modified diagnosis. Pereonite 3 posterolateral margins produced posteriorly, ventral spine present, small. Pereonite 4 lateral margins convex, ventral spine absent. Pleotelson ovoid. Pereopod III ischium dorsal lobe triangular. Operculum elongate, distally tapering, apical width smaller 0.50 operculum width.

Description of non-ovigerous female. Body. Length 2.8–3.2 mm, 4.1 width, subcylindrical; with furry cuticular setules, mainly laterally on tergites V–VII and covering whole pleotelson. Ventral spines. Pereonite 1 spine acute, prominent. Pereonite 3 spine acute, small, placed medially on midline. Pereonite 4 spine absent. Pereonite 5 spine acute, small, closer to posterior segment border. Pereonite 6 spine acute, prominent, closer to posterior segment border. Pereonite 7 spine prominent.

Cephalothorax. Frons straight, frontal furrow present, convex, almost straight, anterior to antennal articulations; posterolateral margins acute. Fossosome. Length 0.82 width, 0.21 body length. Lateral tergite margins confluent, ventral surface without keel; sternite articulations present in rudimental condition. Pereonite 1. Anterior margin concave. Pereonite 3. Posterolateral margin produced posteriorly, tapering, with lateral constriction anteriorly to seta articulations; posterolateral setae bifid, robust, spine-like. Pereonites 4–7. Posterolateral margins produced posteriorly, tapering. Posterolateral setae bifid, robust, spine-like. Pereonite 4. Width 1.1 pereonite 5 width, length 0.33 width; pereonal collum present. Lateral margins simple concave. Pereonite 5. Length 0.48 width, 1.3 pereonite 4 length. Pereonite 6. Length 0.56 width, 1.2 pereonite 5 length. Pereonite 7. Length 0.50 width.

Pleotelson. Length 0.23 body length, 1.4 width, narrower than pereonite 7; ovoid, setal ridges visible, waist present. Width maximum anterior to waist. Statocysts present, dorsal slot-like apertures transverse across longitudinal axis, convex. Posterior apex length 0.15 pleotelson length, concave at uropod insertions, posteriorly convex, evenly rounded.

Labrum. Anterior margin concave. Antennula  . Length 0.23 antenna length, width 0.60 antenna width. Articles decreasing in size from proximal to distal. Articles 1–4 distinctly longer than wide, cylindrical. Article 1 longest and widest, with 3 setae: 2 simple, 1 broom. Article 2 with 5 setae: 2 simple, 3 broom. Article 3 with 1 simple seta. Article 5 minute, squat, with 2 setae: 1 simple, 1 aesthetasc. Antenna. Article 1 squat. Article 2 elongate, longer than article 1. Article 3 elongate, longer than article 1. Article 4 about as long as articles 1–3 together, distally with 2 simple setae. Article 5 shorter than article 4, distally with 2 broom setae. Flagellum with 6 articles.

Mandibles. Left and right mandible incisor processes multidentate with dorsal and ventral subdistal teeth that partly enclose lacinia. Maxilliped. Basis length 2.9 width; epipod length 3.0 width, 1.0 basis length; palp wider than endite, article 2 wider than articles 1 and 3, article 1 longer than article 3.

Pereopod I. Ischium dorsal margin with 3 submarginal setae. Merus dorsally with 5 setae: 4 in submarginal row, 1 bifurcate distally; ventral margin with 2 setae. Carpus dorsally with 1 seta. Dactylus distally with 3 sensillae. Pereopod III. Ischium dorsal lobe triangular; proximally with 4 setae; apex with 1 prominent seta; apical seta robust, bifurcate, recurved, flexibly articulated; distally with 4 setae. Merus dorsally with 11 setae: 4 thin, long, 6 more robust, bifurcate, long, 1 short, spine-like; ventrally with 4 setae. Carpus dorsally with 5 setae, 4 long, bifurcate, 1 broom, ventrally with 5 setae: 4 potentially distally sensillate, 1 short, bifurcate. Dactylus with 3 sensillae. Pereopod IV. Carpus subcylindrical.

Operculum. Elongate, length 1.7 width; apical width 0.47 operculum width; distally tapering; with lateral fringe consisting of 9 setae, distinctly separate from apical row of setae; with 16 pappose setae on apex. Uropod. Length 0.94 pleotelson length; protopod length 8.3 width, 0.69 pleotelson length, protopod distal margin blunt, endopod insertion terminally; endopod length 6.0 width, 0.36 protopod length, width at articulation clearly narrower than protopod.