Macrostylis cerrita Vey & Brix, 2009

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 : 189-190

Macrostylis cerrita Vey & Brix, 2009

urn:lsid:zoobank.org:act:3644D8D7-30A9-462E-9DC1-8D19C948EC9C Macrostylis cerrita Vey & Brix, 2009 ; pp. 356–370, Figs 1–6 .

Modified diagnosis. Body cuticular setules absent. Pereonite 3 posterolateral margins not produced posteriorly. Pereonite 3–4 ventral spines absent. Pereonite 4 lateral margins convex in collum region, concave posteriorly; posterolateral margins not produced posteriorly. Pereonite 7 ventral spine prominent. Pleotelson narrowing evenly towards uropod insertions, lateral margins straight, waist present; posterior apex posteriorly convex, length 0.14 pleotelson length. Pereopod III ischium dorsal lobe tapering, recurved with no apical seta. Pereopod V ischium distodorsally without seta. Operculum elongate, distally tapering, apical width subequal or smaller 0.5 operculum width, lateral fringe of setae distinctly separate from apical row of setae.

Remarks. The original illustration of the habitus (Vey & Brix 2009; Fig. 1 B) shows a conspicuous spine laterally on the pleotelson. This spine was not mentioned in the original description text though. The inspection of the holotype revealed that it does not exist.

The pereopod III ischium dorsal lobe ( Fig. 4 E) is of remarkable shape and setation. It is tapering, recurved and an apical seta is lacking. A similar ischium is present in M. balayevi Mezhov, 1989 M. quadratura Birstein, 1970 and M. tumulosa Mezhov, 1989 where the dorsal lobe is tapering and without apical seta. The recurved apical lobe found in M. cerrita , however, might represent a more derived condition. In other species of the genus, the ischium has a convergently similar, hook-shaped appearance. Instead of a recurved dorsal lobe, however, a hook-shaped apical spine-like seta ( Fig. 22 O) is present on the dorsal lobe apex. This is the case e.g. in Macrostylis carinifera Mezhov, 1988 , M. dorsaetosa Riehl et al., 2012 , M. papillata Riehl et al. 2012 , M. spinifera Sars, 1864 .

Vey and Brix (2009) noticed the lateral mandibular setae and interpreted this character as autapomorphy for M. cerrita . However, the mandibular lateral setae have been recognized already before, e.g. in M. sarsi (Brandt 1992; Fig. 14 ) and M. magnifica Wolff, 1962 (Mezhov 2000) , and are present in all species described since and all type material checked (Riehl, unpublished data). Possibly, those setae are apomorphic for the whole family Macrostylidae .

In accordance with the gender agreement stated in Article 31.2 of the ICZN, the species-group name is changed to be feminine.

Figures

FIGURE 1. Type localities of Macrostylidae from the Southern Ocean. 1) Macrostylis antennamagna Riehl & Brandt, 2010. 2) M. setulosa Mezhov, 1992. 3) M. uniformis Riehl & Brandt, 2010. 4) M. vinogradovae Mezhov, 1992. 5) M. cerrita Ve y & Brix, 2009. 6) M. gerdesi (Brandt, 2002). 7) M. sarsi Brandt, 1992; M. obscura (Brandt, 1992). 8) M. matildae n. sp.; M. scotti n. sp. 9) M. roaldi Riehl & Kaiser, 2012.

FIGURE 2. Macrostylis scotti n. sp. A – E, holotype adult male (ZMH K- 42990), with ciliate epibionts, photoplate. A, dorsal habitus. B, ventral fossosoma. C, ventral pleotelson. D, ventral cephalothorax. E, ciliate epibionts on right lateral margins of tergites 4 – 5. Scales: A = 0.5 mm, B – D = 0.2 mm, E = 0.1 mm.

FIGURE 3. Macrostylis scotti n. sp. A – E, holotype adult male (ZMH K- 42990), with ciliate epibionts. A, lateral habitus, ornamentation omitted, setae simplified, uropods partially omitted. B, dorsal habitus, ornamentation omitted, setae simplified, areas free of imbricate ornamentation indicated by thin dashed lines on pereonites 6 – 7. C, pereopod III, ischium dorsal apex proximal prominent seta damaged. D, ciliate epibiont. E, ventral pleotelson, left setal ridge and ventral setation on left pleopod II omitted. Scales: A, B, E = 0.5 mm, C = 0.3 mm, D = 0.1 mm.

FIGURE 4. Macrostylis scotti n. sp. A – H, paratype non-ovigerous female (ZMH K- 42992). A, dorsal habitus, impricate ornamentation (IO) omitted. B, antennula and antenna, in situ. C, ventral pleotelson, IO omitted. D, lateral habitus, IO omitted, setae simplified. E, ventral pleopod V. F, ventral pleopod IV. G, ventral pleopod III. H, ventral pleopod II (operculum). Scales: A, C, D = 0.5 mm, B = 0.2 mm, E – H = 0.3 mm.

FIGURE 5. Macrostylis scotti n. sp. A – C, paratype non-ovigerous female (ZMH K- 42992). A, pereopod II. B, pereopod IV. C, pereopod III. Scale: A – C = 0.3 mm.

FIGURE 6. Macrostylis scotti n. sp. A – C, paratype non-ovigerous female (ZMH K- 42992). A, pereopod V. B, pereopod VI. C, pereopod VII. Scale: A – C = 0.3 mm.

FIGURE 14. Macrostylis matildae n. sp. A – H, paratype non-ovigerous female (ZMH K- 43003). A, left mandible, dorsal, molar process damaged. B, left mandible incisor process and lacinia mobilis, medial. C, right mandible incisor process and lacinia mobilis, medial. D, right mandible, dorsal, molar process damaged, lateral seta missing. E, antennula and antenna, in situ. F, maxillula, damaged. G, maxilliped, ventral. H, maxilla. Scales: A – H = 0.1 mm.

FIGURE 22. Illustrations for identification key to the Macrostylidae of the Southern Ocean. A, pleotelson of Macrostylis cerrita Vey & Brix, 2009, dorsal view, evenly narrowing towards uropodal insertions, lateral margins straight, waist absent. B, pleotelson of M. matildae n. sp., dorsal view, evenly narrowing towards uropodal insertions, lateral margins straight, waist present. C, pleotelson of M. gerdesi (Brandt, 2002), dorsal view, lateral margins straight, subparallel. D, pleotelson of Macrostylis setulosa Mezhov, 1992, lateral margins convex, waist present. E, pleotelson of M. antennamagna Riehl & Brandt, 2010, dorsal view, lateral margins convex, waist present, posterior apex concave. F, ventral spines of M. matildae with pereonites 3 and 4 spines present, pereonite 7 spine small. G, ventral spines of M. roaldi Riehl & Kaiser (2012) with pereonites 3 and 4 spines present, pereonite 7 spine prominent. H, ventral spines of M. scotti n. sp. with pereonites 3 and 4 spines absent, pereonite 7 spine small. I, M. matildae pereonite 3 posterolateral margin spine-like setae absent, pereonite 4 lateral margin curved, posterolateral margin produced posteriorly, rounded, spine-like setae present. J, M. scotti pereonite 3 posterolateral margin spine-like setae absent, pereonite 4 lateral margin convex, posterolateral margin not produced posteriorly, rounded, spine-like setae absent. K, M. roaldi pereonite 3 posterolateral margin spine-like setae present, pereonite 4 lateral margin curved, posterolateral margin produced posteriorly, pointed, spine-like setae present. L, M. matildae operculum, elongate, distally tapering, with lateral fringe of setae distinctly separate from apical row of pappose setae. M, M. scotti operculum, elongate, ovoid, with fluent transition between lateral fringe of setae and apical row of pappose setae. N, M. roaldi operculum, stout, ovoid, with lateral fringe of setae distinctly separate from apical row of pappose setae. O, M. cerrita pereopod III ischium with tapering dorsal apex and 1 spine-like prominent seta. P, M. roaldi pereopod III ischium with triangular dorsal apex and 1 prominent spine-like seta. Q, M. scotti pereopod III ischium with dorsal apex tapering and 2 prominent, spine-like setae.