Austrosignum glaciale Hodgson 1910

Austrosignum glaciale Hodgson, 1910

Figs 2–4

Austrosignum glaciale Hodgson, 1910:68, pl.X, fig.2; Menzies, 1962:50.

Austrosignum grande Hodgson, 1910:66, pl.X, fig.1; Menzies, 1962:50.

Munnogonium grande (Hodgson, 1910). — Bowman & Schultz, 1974:266.

Austrosignum grande Hodgson, 1910. — Kussakin, 1982:94 (senior synonym of A. glaciale) Austrosignum grande Hodgson, 1910. —Junior synonym of A. glaciale. Corrected synonymy, herein. Not Paramunna antarctica (Richardson, 1906) of Hale (1937). — Menzies, 1962:52

Type fixation. Lectotype, Ψ, NHM 1910.3.18.147. — Here designated

Material examined. Lectotype. Ovigerous Ψ, 2.1 mm, Winter Quarters, McMurdo Bay, Ross Island, Antarctica, 77°51'S 166°36'E, inside 20-fathom line [36.5 m], January 1902, 'Discovery' coll., NHM 1910.3.18.147.

Paralectotypes. 1 preparatory Ψ, 1 young Ψ, same data as lectotype, NHM 1910.3.18.148–149.

Other material. 1 large terminal ɗ (2.8 mm), 1 small ɗ, 1 preparatory Ψ, (syntypes of Austrosignum grande Hodgson, 1910), Winter Quarters, McMurdo Bay, Ross Island, Antarctica, 77° 51'S 166° 36'E, inside 20-fathom line [36.5 m], February and March 1902, 'Discovery' coll., NHM 1910.3.18.144–146. 1 specimen, North Bay off Cape Evans, McMurdo Sound, Ross Island, Antarctica, 77° 38.17'S, 166° 24.5'E, on sponge, 18 m, G.D. Wilson and T.E. DeLaca by hand on SCUBA, 20 December 1976, AM P64142. 12 ɗ, 1 Ψ, Davis Station, Antarctica, 68o 34.5'S, 77o 53'E, M. Tucker, site C, 25 January 1982, NMV J4765. 1 spent Ψ, Davis Station, Antarctica, 68o 34.5'S, 77o 7'E, M Tucker, site 9, 1 January 1982, NMV J4776. 1 spent Ψ, Davis Station, Antarctica, 68o 38'S, 77o 48'E, M. Tucker, site 9, 21 December 1981, NMV J4778.

Description. Body ovate; width 0.55 length in female, width 0.47–0.51 length in male (larger value - terminal male), widest at pereonites 3. Head longer in male than female, length 0.44–0.50 width (larger value subterminal male), length 0.42 width; length posterior to eyestalks 1.1 anterior length in female, 1.5 anterior length in male. Frontal margin without angular lateral margins adjacent to antennae, shallow convex, almost straight medially. Eyestalks in female length 4.0 width, male length 3.5–6.3 width (larger value terminal male), apex rounded, long axis angling forward at approximately 30° in female, 40° in male.

Pereonites 1–4 lateral margins not projecting, coxae visible in dorsal view (coxae II-IV not visible in adult females). Pereonite 1 of terminal male greatly enlarged. Pereonite 1 sagittal length in female 1.8 pereonites midline length, in male 1.9 pereonites midline length. Pereonite 1–7 lateral margin rounded.

Pleon length 1.90 width in female, 1.60 width in male (n=2). Pleonite 1 width 0.86–0.91 distance between uropods (largest non-terminal male, n=3), length 0.4 width. Pleotelson laterally rounded, lacking inflection between lateral and proximal margins; length in ventral view proximal to pleopod insertion 0.26 total pleotelson length; lateral margin with proximal neck before convex margin; lateral margins smooth; posterior margin forming 80° angle, evenly curving into lateral margin, apex more broadly rounded in terminal male.

Antennula articles 1–2 combined extending beyond eyestalk apex; article 1 shorter than 2, width subequal to 2, tubular; 4–6 of subequal length, shorter than 3 (3 nearly as long as 4–6 combined).

Antenna article 3 in ventral view tubular, width 0.44 length, 5 only slightly longer than article 4; flagellum with 6 articles, proximal article subequal to next article.

Pereopod I basis anterior margin smooth, length 2.6–3.5 width (largest value female); carpus distal width 0.72–0.96 posterior margin length (largest value terminal male), posterior margin robust setae shafts straight, posterior margin with single spine proximal to robust setae, with crenate ridges (cuticular combs) on square spine between main robust setae; propodus narrowing distally to insertion of dactylus, with crenate ridge on opposing margin.

Male pleopods I lateral lobes distinctly projecting from midlateral margin, width 0.4 distance to midline; distal projection length 0.31 pleopod total length, forming acute angle, with pointed apices. Female operculum ovoid, width 0.67 length.

Uropods dorsal and directly adjacent to lateral margin of pleotelson.

Size. Largest ɗ, 2.8 mm; largest Ψ, 2.2 mm.

Distribution. McMurdo Sound to Adelie Land, Antarctica. 18– ca. 36 m.

Remarks. The following reports with illustrations of Austrosignum glaciale and A. grande represent incorrect identifications. Austrosignum glaciale, Vanhöffen (1914): we have examined Vanhöffen’s material and have found that none of the specimens belong in Austrosignum. The bulk of the specimens represent an undescribed species that does not fit Cryosignum, either. A few specimens represent other undescribed species. A. glaciale, Monod (1931; not seen, see Cryosignum gen. nov. below), A. glaciale, Nordenstam (1933; see Cryosignum gen. nov. below), A. grande, Menzies (1962; see Cryosignum gen. nov. below); Menzies (1962, caption for his fig. 11) stated that the specimen illustrated by him is the holotype of Austrosignum grande. This is incorrect; the only specimen examined by Menzies was the male from southern Chile listed in his ‘Material examined’.