The effects of depth, distance, and the Mid-Atlantic Ridge on genetic differentiation of abyssal and hadal isopods (Macrostylidae)

The largest habitat on Earth, the abyssal oceans below 3500 m depth, is commonly assumed to represent a continuous environment due to homogeneity of environmental factors and the lack of physical barriers. Yet, the presence of bathymetric features, such as Mid-Ocean Ridges, and hadal trenches provide a discontinuation. During the Vema-TRANSIT expedition in 2014/2015 to the tropical North Atlantic, a transatlantic transect was studied following the full extent of the Vema Fracture Zone in an east-west direction and including the Puerto Rico Trench (PRT). The aim of this study was to test whether large bathymetric features represent barriers to dispersal and may lead to differentiation and eventually speciation. In this study, these potential barriers included the Mid-Atlantic Ridge (MAR) and the transition (similar to 3000 m) from the hadal PRT to the adjacent abyss. Genetic differentiation and differences in community structure (species composition) from east and west of the MAR, as well as abyssal and hadal depth zones were tested for using the poor dispersers Macrostylidae (Crustacea, Isopoda) as a model Distribution patterns showed that certain macrostylid species have ranges extending more than 2000 km, in some cases across oceanic ridges and trench-abyss transitions. Contrastingly, there was a clear signal for geographic population structure coinciding with the east-west division of the Atlantic by the MAR as well as with the abyss-hadal zonation. These results support the hypotheses that depth gradients as well as oceanic ridges reduce dispersal even though barriers may not be absolute. Additionally, positive correlation between genetic- and geographic distances showed that the vast size of the deep sea itself is a factor responsible for creating diversity

Hylarana Raniceps (White-lipped Frog). Predation

We relate herein an observation of the predation of a Hylarana raniceps metamorph by a spider. H. raniceps is a common species in the lowlands of Bornean dipterocarp forests. In March 2007, we observed a “fishing spider” of the species Thalassius cf. albocinctus (Doleschall, 1859) at a alluvial pond off Headhunters’ Trail, near Camp 5 (04.139056°N, 114.899944°E), Gunung Mulu National Park, Sarawak, East Malaysia (Borneo), with a metamorph of H. raniceps as prey

Discovery of widely available abyssal rock patches reveals overlooked habitat type and prompts rethinking deep-sea biodiversity

Habitat heterogeneity and species diversity are often linked. On the deep seafloor, sediment variability and hard-substrate availability influence geographic patterns of species richness and turnover. The assumption of a generally homogeneous, sedimented abyssal seafloor is at odds with the fact that the faunal diversity in some abyssal regions exceeds that of shallow-water environments. Here we show, using a ground-truthed analysis of multibeam sonar data, that the deep seafloor may be much rockier than previously assumed. A combination of bathymetry data, ruggedness, and backscatter from a trans-Atlantic corridor along the Vema Fracture Zone, covering crustal ages from 0 to 100 Ma, show rock exposures occurring at all crustal ages. Extrapolating to the whole Atlantic, over 260,000 km2 of rock habitats potentially occur along Atlantic fracture zones alone, significantly increasing our knowledge about abyssal habitat heterogeneity. This implies that sampling campaigns need to be considerably more sophisticated than at present to capture the full deep-sea habitat heterogeneity and biodiversity

Marine lebensspuren: improving the classification of seafloor traces from underwater imagery and observations

Project PID2019-104625RB-100 funded by MCIN/AEI/10.13039/50110001103

Ocean Species Discoveries 1–12 — A primer for accelerating marine invertebrate taxonomy

Discoveries of new species often depend on one or a few specimens, leading to delays as researchers wait for additional context, sometimes for decades. There is currently little professional incentive for a single expert to publish a stand-alone species description. Additionally, while many journals accept taxonomic descriptions, even specialist journals expect insights beyond the descriptive work itself. The combination of these factors exacerbates the issue that only a small fraction of marine species are known and new discoveries are described at a slow pace, while they face increasing threats from accelerating global change. To tackle this challenge, this first compilation of Ocean Species Discoveries (OSD) presents a new collaborative framework to accelerate the description and naming of marine invertebrate taxa that can be extended across all phyla. Through a mode of publication that can be speedy, taxonomy-focused and generate higher citation rates, OSD aims to create an attractive home for single species descriptions. This Senckenberg Ocean Species Alliance (SOSA) approach emphasises thorough, but compact species descriptions and diagnoses, with supporting illustrations and with molecular data when available. Even basic species descriptions carry key data for distributions and ecological interactions (e.g., host-parasite relationships) besides universally valid species names; these are essential for downstream uses, such as conservation assessments and communicating biodiversity to the broader public

Macrostylis antennamagna Riehl & Brandt 2010

Macrostylis antennamagna Riehl & Brandt, 2010 urn:lsid:zoobank.org:act: 5 B09C 3 B 7-6291 - 458 D-BC 5 E- 975 BCBD 39 D 80 Macrostylis antennamagna Riehl & Brandt, 2010; pp. 29–43; Figs 9–18. Modified diagnosis. Body hirsute. Female pleotelson narrowing evenly towards uropod insertions, lateral margins straight, posterior apex slightly concave, posterior apex length 0.15 pleotelson length. Male pleotelson of hourglass-like shape, posterior apex clearly concave. Female pereonite 4 posterolateral margins produced posteriorly, rounded. Male pereonite 4 posterolateral margins not produced posteriorly. Female pereonite 6 shorter pereonite 5, vice versa in male. Female pereonite 3–4 ventral spines present, small, both absent in male. Female and male pereonite 7 ventral spine small. Pereopod III ischium dorsal lobe triangular.Published as part of Riehl, Torben & Brandt, Angelika, 2013, Southern Ocean Macrostylidae reviewed with a key to the species and new descriptions from Maud Rise, pp. 160-203 in Zootaxa 3692 (1) on page 189, DOI: 10.11646/zootaxa.3692.1.10, http://zenodo.org/record/22061

Macrostylis obscura Brandt 1992

Macrostylis obscura (Brandt, 1992) nom. dub. Desmostylis obscura Brandt, 1992; p. 70, Figs 11–13; Macrostylis obscura (Brandt, 1992); Riehl & Brandt (2010); pp. 43–44; Fig. 19. Remarks. This species and the genus Desmostylis Brandt, 1992 were based on a single damaged manca. Both were subsequently transferred to Macrostylis Sars, 1864 (Riehl & Brandt 2010). The species was collected from the same box corer sample as M. sarsi Brandt, 1992, which is represented by a single subadult female specimen. Both species share several similarities, such as dorsal and lateral setation of the body. Quantitative samples such as boxcorer samples often show an aggregated distribution of single species, so the possibility remains that these specimens are conspecific. Unfortunately, much of each type specimen is missing owing to dissection and subsequent damage and loss at the NHM London. So the types cannot be fully compared to decide whether they are conspecific or not. Another consequence of the manca stage of the only known representative of M. obscura is that information suitable and available for comparison with other species of the family is very limited. M. obscura is therefore not included in the key presented below and is henceforward regarded nomen dubium. In accordance with the gender agreement stated in Article 31.2 of the ICZN, the species-group name is changed to be feminine.Published as part of Riehl, Torben & Brandt, Angelika, 2013, Southern Ocean Macrostylidae reviewed with a key to the species and new descriptions from Maud Rise, pp. 160-203 in Zootaxa 3692 (1) on page 190, DOI: 10.11646/zootaxa.3692.1.10, http://zenodo.org/record/22061

Macrostylis roaldi Riehl & Kaiser 2012

Macrostylis roaldi Riehl & Kaiser, 2012 urn:lsid:zoobank.org:act: 5 ABAAC 9 D- 3925 - 4 A 67 -A009- 84 EA 398 C 88 AA Modified diagnosis. Pereonite 3 posterolateral margins produced posteriorly, tapering; posterolateral setae spinelike. Pereonite 3–4 ventral spines present, prominent. Pereonite 4 lateral margins concave in collum region, medially convex with greatest width, constricted anterior to posterolateral margin. Female pleotelson ovoid, waist present. Male pleotelson trapezoid, widening towards uropod insertions, lateral margins straight. Pereopod III ischium dorsal lobe triangular with 1 prominent, spine-like, bifid apical seta. Operculum stout, ovoid, apical width greater 0.5 operculum width, lateral fringe of setae distinctly separate from apical row of setae.Published as part of Riehl, Torben & Brandt, Angelika, 2013, Southern Ocean Macrostylidae reviewed with a key to the species and new descriptions from Maud Rise, pp. 160-203 in Zootaxa 3692 (1) on page 191, DOI: 10.11646/zootaxa.3692.1.10, http://zenodo.org/record/22061

Macrostylis matildae Riehl & Brandt, 2013, n. sp.

Macrostylis matildae n. sp. (Figs 11–20) urn:lsid:zoobank.org:act:CBDDFFA 0-5539 - 4540 -B04E-AA 9 CA 1 D 695 A 5 Etymology. The name “ matildae ” is the latinized genitive case of “Matilda”, an Old German given name meaning “powerful battler”. It is derived from “Maud”, another variant of the same name, as in Maud Queen consort of Norway (1869–1938), spouse of King Haakon VII. This name is ment to reflect on the type locality seamount Maud Rise and the adjacent Norwegian claim of Antarctica, Queen Maud Land (Norwegian: Dronning Maud Land). Type fixation. Holotype (Fig. 11): non-ovigerous female, 1.7 mm, ZMH K- 43000, designated here. Type material examined. Holotype: non-ovigerous female used for habitus illustrations, 1.7 mm, ZMH K- 43000. Paratypes (all from same sample as holotype): 1 ovigerous female with eggs used for habitus illustrations, 2.0 mm, ZMH K- 43002; 1 non-ovigerous female dissected for illustrations, 1.9 mm, ZMH K- 43003; 1 nonovigerous female used for SEM, ZMH K- 43005; 1 adult male, dissected for illustrations, ZMH K- 43004; 1 manca male, dissected for illustration ZMH K- 43001; 29 specimens from the type locality: 6 ovigerous females with no eggs; 14 non-ovigerous females; 1 female manca ZMH; 1 manca male ZMH K- 43006. Type locality. Collected 04th January 2008 from the slope of the seamount Maud Rise. This is located off Queen Maud Land on the Antarctic continental slope. Samples were taken during the ANDEEP-SYSTCO project with R/V Polarstern, station ANTXXIV- 2 039– 17: start trawl at 64 ° 28.77 ’ S, 2 ° 52.69 ’ E; 2,152 m depth; end trawl at 64 ° 28.66 ’ S, 2 ° 53.14 ’ E; 2,153 m depth. Diagnosis. Body and all external appendages covered with furry coat of cuticular setules. Pereonites 3–4 ventral spines present. Pereonite 4 posterolateral margins produced posteriorly, rounded. Female pereonite 6 length clearly larger pereonite 5 length. Pereonite 7 ventral spine small; posterolateral margins similar in female and male. Pleotelson shape similar in both sexes, narrowing evenly towards uropod insertions, lateral margins straight, waist present; posterior apex convex, apex length about 0.13 pleotelson length. Pereopod III ischium dorsal lobe triangular, apex with 1 prominent recurved seta. Operculum stout. Uropods and pleotelson respectively of similar length in adult male and female. Description of non-ovigerous female. Body (Figs 11 A,B, 12 A, 13 A,B). Length 1.7–1.9 mm, 3.8 –4.0 width, subcylindrical, tergite surfaces hirsute, densely covered with cuticular setules on all body parts, incl. pereopods and operculum. Ventral spines. All spines acute. Pereonite 1 spine prominent. Pereonite 3 spine prominent, closer to anterior segment border. Pereonite 4 spine directed posteriorly, small, closer to posterior segment border. Pereonite 5–6 spines prominent, closer to posterior segment border. Pereonite 7 spine small. Imbricate ornamentation (IO). Cephalothorax IO dorsally and laterally; pereonite 1 –pleotelson IO on all tergites and sternites. Cephalothorax. Length 0.73–0.84 width, 0.16–0.18 body length; frons convex, with wrinkles, frontal furrow present, slightly convex; dorsal surface with array of setae, in symmetrical arrangement: each side with 3 setae in a transversal row along frontal furrow, 1 seta posteromedially to antennal insertions, 2 setae along posterolateral ridge. Posterolateral setae present, robust, flexibly articulated. Posterolateral margins acute. Fossosome. Length 0.84–0.95 width, 0.22–0.24 body length. Lateral tergite margins confluent, ventral surface without keel; sternite articulations present, fully expressed, clearly reaching tergal margin. Pereonite 1. Anterior margin concave; posterolateral setae simple. Pereonite 2–3. Posterolateral setae simple, flexibly articulated. Pereonite 4. Width 1.1 pereonite 5 width, length 0.34–0.41 width; pereonal collum present. Lateral margins curved, narrow in pereonal collum, widest in the middle and slightly concave anterior of posterolateral angles. Posterior tergite margin with 4 simple, thin, flexibly articulated setae; setae extending beyond posterior margin. Posterolateral margins produced posteriorly, rounded. Posterolateral setae bifid, robust, spine-like. Pereonites 5–7. Posterolateral margins produced posteriorly, rounded. Posterolateral setae bifid, robust, spinelike. Pereonite 5. Length 0.42–0.43 width, 0.86–0.94 pereonite 4 length. Posterior tergite margin with 6 simple, flexibly-articulated setae; setae not extending beyond posterolateral margin. Pereonite 6. Length 0.50–0.52 width, 1.1–1.2 pereonite 5 length. Posterior tergite margin with 10 simple, flexibly articulated setae; setae extending beyond posterolateral angles. Pereonite 7. Length 0.44–0.51 width. Posterior tergite margin with 11–15 simple, flexibly articulated setae; setae extending beyond posterolateral margin. Pleonite 1. Sternal articulation with pleotelson absent. Pleotelson (Figs 11 A,D, 13 B). Narrowing evenly towards uropod insertions, lateral margins straight, waist present, setal ridges visible in dorsal view, dorsal length 0.22–0.23 body length, 1.4–1.6 width, narrower than pereonite 7; statocysts present, dorsal slot-like apertures present, diagonal across longitudinal axis, concave. Posterior apex slightly concave at uropod insertions, posteriorly convex, length 0.13 pleotelson length. Posterior apex with 10 pappose setae, positioned on and around apex. Pleopodal cavity width 0.75–0.78 pleotelson width, pre-anal trough width 0.38–0.42 pleotelson width. Anal opening terminally, parallel to frontal plane. Labrum. Anterior margin convex. Antennula (Fig. 14 E). Length 0.38 head width, 0.22 antenna length, width 0.69 antenna width. Articles decreasing in width from proximal to distal. Articles 1–4 distinctly longer than wide, cylindrical. Article 1 with 1 broom seta. Article 2 longer than article 1, with 2 broom setae. Article 3 with 1 broom seta. Article 5 squat, with 2 setae: 1 simple, 1 aesthetasc with intermediate belt of constrictions. Antenna (Fig. 14 E). Length 0.36 body length. Article 1 squat. Articles 2–3 elongate, longer than article 1. Article 4 longer than articles 1–3 together, distally with 1 simple seta. Article 5 length subequal article 4 length, distally with 3 broom setae. Flagellum with 7 articles. Mandibles (Fig. 14 A–D). In medial view strongly narrowing from proximal to distal; left and right mandible incisor processes multidentate with dorsal and ventral subdistal teeth that partly enclose lacinia, left incisor with 4 cusps, lacinia mobilis grinding, with 4 cusps; right mandible incisior with 3 cusps, lacinia mobilis grinding, clearly smaller than left lacinia, with 4 cusps. Maxillula (Fig. 14 F). Lateral lobe with 12 robust setae. Maxilla (Fig. 14 H). Lateral lobe with 3 setae terminally; middle endite with 4 setae terminally; inner endite with 8 setae terminally. Maxilliped (Fig. 14 G). Basis length 3.3 width, medioventrally with seta present; epipod length 2.7 width, 0.99 basis-endite length; palp wider than endite, article 2 wider than articles 1 and 3, article 1 shorter than article 3. Pereopod I (Fig. 15 A). Length 0.45 body length. Ischium dorsal margin with 5 setae: 1 small proximally, 4 long, thin submarginally. Merus dorsal margin with 4 submarginal setae: 3 long thin, 1 short, bifurcate; ventral margin with 2 medially serrate, distally f ringe-like sensillae. Carpus dorsally with 2 long, thin setae. Dactylus distally with 3 sensillae. Pereopod II (Fig. 15 B). Length 0.47 body length. Ischium dorsally with 3 submarginal setae: 1 small proximally, 2 long, thin distally. Merus dorsally with 4 submarginal setae: 3 long and thin, and 1 short, bifurcate; ventrally with 3 medially serrate, distally fringe-like sensillae. Carpus dorsally with 3 long, thin setae; ventrally with 5 setae: 4 medially serrate, distally fringe-like sensillae, 1 short bifurcate. Dactylus distally with 3 sensillae. Pereopod III (Figs 11 C, 12 D, 15 C). Length 0.47 body length. Ischium dorsal lobe triangular; proximally with 2–3 setae; apex with 1 prominent seta; apical seta robust, bifid, bent towards proximal, spine-like; distally with 1–2 setae. Merus dorsally with 4–6 setae: 1–2 long, thin and 2–4 long, bifurcate; ventrally with 3 medially serrate, distally fringe-like sensillae. Carpus dorsally with 5–6 setae: 4–5 long, bifurcate, 1 broom; ventrally with 4–5 setae: 3–4 medially serrate, distally fringe-like sensillae, 1 short bifurcate. Dactylus distally with 3 sensillae. Pereopod IV (Figs 12 C, 15 D). Length 0.25 body length, carpus cylindrical. Pereopod V (Fig. 16 A). Length 0.40 body length. Ischium middorsally with 2 setae; distodorsally without seta; midventrally with 1 seta; distoventrally with 3 setae. Merus distodorsally with 4 setae: 2 bifurcate, 2 simple; midventrally with 1 seta; distoventrally with 2 setae: 1 simple, 1 bifurcate. Carpus distodorsally with 1 seta; distoventrally with 3 bifurcate setae. Pereopod VI (Fig. 16 B). Length 0.51 body length. Ischium dorsally with 2 setae; midventrally with 4 setae, arranged in bundle; distoventrally with 2 setae. Merus middorsally without seta; distodorsally with 6 setae; midventrally with 2 bifurcate setae, arranged in bundle; distoventrally with 2 setae: 1 long, 1 bifurcate. Distodorsally with 3 setae: 1 broom, and 2 bifurcate; midventrally with 2 bifurcate setae; distoventrally with 4 bifurcate setae. Pereopod VII (Fig. 16 C). Length 0.35 body length; basis length 3.8 width, dorsal margin with row of 14 elongate setae, exceeding beyond proximal half of article; setae longer basis width; ventral margin with 2 setae; setae shorter basis width. Ischium length 2.3 width, middorsally with 2 setae, midventrally and distoventrally with 1 seta respectively. Merus length 2.3 width; distodorsally with 3 setae; midventrally and distoventrally with 1 seta respectively. Carpus length 4.7 width, distodorsally with 4, midventrally with 1, distoventrally with 3 bifurcate setae respectively. Propodus length 5.5 width. Dactylus length 4 width. Operculum (Figs 11 D, 13 C). Elongate, length 1.6 width, 0.83 pleotelson dorsal length; apical width 0.52 operculum width; distally tapering, not reaching anus; without keel. With lateral fringes of 7–10 setae, distinctly separate from apical row of setae. With 10 pappose setae on apex, completely covering anal opening. Pleopod III (Fig. 13 D). Length 2.8 width; protopod length 2.3 width, 0.56 pleopod III length; exopod with fringe of fine setae; setae longer than pleopod III exopod width, length 0.64 pleopod III length, seta subterminally present. Pleopod V (Fig. 13 F). Present. Uropod (Figs 11 A, 12 A, 13 B). Inserting on pleotelson posterior margin; length 1.0– 1.1 pleotelson length; protopod length 8.8 –10.0 width, 0.77–0.88 pleotelson length, protopod distal margin blunt, endopod insertion terminal; endopod length 4.5 width, 0.26–0.30 protopod length, width at articulation narrower than protopod. Description of adult male. Body (Fig. 17 A,B). Length 2.6 mm, 4.2 width. Cephalothorax. Length 0.77 width, 0.14 body length. Fossosome. Not keeled. Pereonites 1-3. With 2, 3, 6–7 long, thin posterolateral setae respectively. Pereonite 4. Length 0.52 width. Pereonal collum present, medially convex. Posterolateral margins produced posteriorly. Pereonite 5. Length 0.59 width. Pereonite 6. Length 0.55 width, 0.90 pereonite 5 length. Pereonite 7. Posterior tergite margin with 15 simple, asetulate, flexibly articulated setae; setae not extending beyond posterolateral margin. Pleonite 1. Sternal articulation with pleotelson present. Pleotelson (Fig. 17 B,C). Similar to female. Posterior apex length 0.10 pleotelson length, pleopodal cavity width 0.67 pleotelson width, pre-anal trough width 0.33 pleotelson width. Antennula (Fig. 17 D). Length 0.39 head width, width 1.3 antenna width. Article 1 elongate, longest and widest, with 1 broom seta. Article 2 elongate, with 3 distally fringe-like sensillae. Article 3 squat, with 2 simple setae. Article 4 squat, with 6 aesthetascs. Article 5 squat, with 6 setae: 1 simple, 5 aesthetascs. Aesthetascs with intermediate belt of constrictions. Antenna (Fig. 17 D). Damaged. Article 1 squat. Article 2 squat, longer than article 1. Article 3 elongate, longer than article 1. Pereopod I (Fig. 18 A,B). Length 0.36 body length. Ischium dorsally with 4 setae. Carpus dorsally with 2 setae: 1 broom, 1 simple; ventrally with 3 setae: 2 medially serrate, distally fringe-like sensillae, 1 small simple. Pereopod II (Fig. 18 C). Length/body-length ratio smaller than in female: length 0.41 body length. Ischium dorsally with 5 long, thin setae. Merus dorsally with 3 setae; ventrally with 3 medially serrate, distally fringe-like sensillae. Carpus dorsally with 3 setae: 2 long, thin, 1 broom; ventrally with 5 setae: 4 medially serrate, distally fringe-like sensillae, 1 small, simple. Pereopod III (Fig. 18 D,E). Length 0.44 body length. Ischium dorsal lobe triangular, proximally with 3 simple setae; apex with 1 prominent, robust, spine-like, bifid seta; distally with 3 simple setae. Merus dorsally with 7 setae: 1 long, thin, simple, 6 bifurcate; ventrally with 3 medially serrate, distally fringe-like sensillae. Carpus dorsally with 5 setae: 4 bifurcate, 1 broom; ventrally with 4 setae: 3 medially serrate, distally fringe-like sensillae, 1 short bifurcate. Pereopod IV (Fig. 18 F,G). Length 0.23 body length. Pereopod V (Fig. 19 A,B). Ischium middorsally with 1 seta, distodorsally with 2 bifurcate setae; midventrally with 3 setae in bundle; distoventrally with 2 setae. Merus distodorsally with 3 setae: 1 long, slim, 2 short, bifurcate; midventrally with 1 bifurcate seta; distoventrally with 3 setae: 1 bifurcate, 1 simple. Carpus distodorsally with 2 setae: 1 broom, 1 simple; distoventrally with 4 short, bifurcate setae. Pereopod VI (Fig. 19 C). Length 0.36 body length. Ischium setation as in female: dorsally with 2 setae; midventrally with 4 setae in bundle; distoventrally with 3 setae. Merus distodorsally with 4 setae: 1 short, bifurcate, 3 simple; midventrally with 1 bifurcate seta; distoventrally with 2 setae: 1 bifurcate, 1 long, simple. Carpus middorsally with 1 bifurcate seta; distodorsally with 4 setae: 1 broom, 3 bifurcate; midventrally with 2 bifurcate setae; distoventrally with 3 bifurcate setae. Pereopod VII (Fig. 19 D). Shorter pereopod VI; basis length 3.0 width; dorsal margin with row of 19 elongate setae exceeding proximal half of article; setae longer basis width; ventral margin with 3 setae; setae shorter basis width; ischium length 3.0 width; middorsally with 2 setae; midventrally with 3 setae; distoventrally with 3 setae. Merus length 2.8 width, setation as in female; carpus length 9.0 width; distodorsally with 4 setae: 1 broom, 3 bifurcate; midventrally with 3 bifurcate setae; distoventrally with 2 bifurcate setae. Propodus length 8.5 width. Dactylus length 5.0 width. Pleopod I (Fig. 17 E). Length 0.66 pleotelson length, lateral horns not extending distally beyond medial lobes; distally with 8–9 sensillae, ventral setae present. Pleopod II (Fig. 17 F). Protopod apex rounded, with 15 setae on proximolateral margin; with 7 pappose setae distally. Endopod distance of insertion from protopod distal margin 0.37 protopod length. Stylet weakly curved, not extending to distal margin of protopod, length 0.40 protopod length. Uropod (Fig. 17 B). Length 0.97 pleotelson length; protopod length 9.2 width; endopod length 0.22 protopod length, less than in female, length 5.0 width. Remarks. The pleotelson of the best intact adult male specimen available is strongly damaged. This might have affected the measurements related to the pleotelson width. The most distinct character state of this species is the dense coat of cuticular setules covering all body parts and external appendages. Different from other species of which both adult sexes have been described, no dimorphism can be found in the shape and size ratios of the pleotelson and uropods. Setal microstructures might have been overlooked in several instances due to the small size of the specimens. There are some indications for several pereopodal setae for which not further attributes were described to be mono- or bisetulate. Macrostylis matildae n. sp. can be regarded closely related to several species from the Southern and Indian Oceans: M. expolita Mezhov, 2003 b, M. latiuscula Mezhov, 2003 b, M. medioxima Mezhov, 2003 a, M. sarsi Brandt, 1992, M. setulosa Mezhov, 1992, and M. vinogradovae Mezhov, 1992. This is due to the similar body shape and ventral spination; body covered with cuticular setules; pereonite 3 posterolateral spine-like setae absent (not in M. setulosa); pereonite 4 posterolateral spine-like setae present; operculum distally narrowing with lateral fringe of setae distinctly separate from apical row of setae.Published as part of Riehl, Torben & Brandt, Angelika, 2013, Southern Ocean Macrostylidae reviewed with a key to the species and new descriptions from Maud Rise, pp. 160-203 in Zootaxa 3692 (1) on pages 178-189, DOI: 10.11646/zootaxa.3692.1.10, http://zenodo.org/record/22061

Macrostylis uniformis Riehl & Brandt 2010

Macrostylis uniformis Riehl & Brandt, 2010 urn:lsid:zoobank.org:act: 5105 DA 6 E-E 793 - 42 B 6 -A 5 D 7 -A 4 D 9 F 8 C 5933 A Macrostylis uniformis Riehl & Brandt, 2010; pp. 19–29, Figs 3–8. Modified diagnosis. Body heavily calcified, cuticular setules absent. Pereonite 4 width subequal pereonite 5 width, lateral margins convex, posterolateral margins not produced posteriorly, posterolateral setae absent. Pleotelson ovoid, waist absent, posterior apex length about 0.20 pleotelson length. Antenna article 2 elongate, longer than article 1. Mandible incisors simplified, monodentate, bluntly rounded. Pereopod III ischium dorsal lobe tapering, with 2 prominent apical setae. Pereopod V ischium distodorsally with setae present. Operculum ovoid, lateral fringe of setae with fluent transition to apical row of setae. Uropod protopod distal margin slightly extending laterally, endopod articulation subterminally.Published as part of Riehl, Torben & Brandt, Angelika, 2013, Southern Ocean Macrostylidae reviewed with a key to the species and new descriptions from Maud Rise, pp. 160-203 in Zootaxa 3692 (1) on page 193, DOI: 10.11646/zootaxa.3692.1.10, http://zenodo.org/record/22061