Natatolana obtusata ( Vanhöffen, 1914 )

Keable, Stephen J., 2006, Taxonomic Revision of Natatolana (Crustacea: Isopoda: Cirolanidae), Records of the Australian Museum 58 (2), pp. 133-244 : 209

Natatolana obtusata ( Vanhöffen, 1914)

Cirolana obtusata Vanhöffen, 1914: 496 , fig. 34.– Tattersall 1921: 205.–? Stephensen, 1947: 496, fig. 8.

Natatolana obtusata .– Bruce, 1981: 958.– 1986: 222.– Brandt, 1988: 120, figs. 56–60.– Brusca et al., 1995: 82.

Type material. Lectotype designated by Brandt (1988): 3, 38 mm, originally ZMG but now in SIF ZMG 262 (not examined) . Paralectotypes: 3, 27 mm, 5♀♀, 19 mm, 20 mm, 27 mm, 28 mm, 30 mm, SIF ZMG 263 ; 233, ZMUC CRU155 ; 2♀♀, ZMUC CRU156 —apparently part of original syntype series from the type locality donated by the Zoological Museum , Berlin , in 1926 (examined). Other possible paralectotypes are: 3♀♀, ZMB 17605; 2♀♀, ZMB 17607—all from type locality ( Brandt, 1988) (not examined). Type locality: off Gauss Station, Posadowsky Bay, Antarctica, 66°2.9'S 89°38.5'E, 385 m, [Deutsche Sudpolarexpedition 1901–1903] .

Diagnosis. Eyes: well developed; elongate, length c. 2× height. Interocular furrow: moderately developed, distinct but not extending across the cephalon. Frontal lamina: lateral margins straight, parallel. Antenna: c. 0.3× as long as body, reaching to posterior of pereonite 3. Coxal plates: furrows strongly developed, on all coxae. Pleonite 4: apex rounded. Pleotelson: broad, length 0.75× basal width; anterodorsal depression absent; anterolateral margins almost straight and angling posteriorly toward the midline; posterolateral margins straight, markedly angled to anterolateral margins and meeting at an obtuse angle; apex produced into a small point; with 10–14 RS. Pereopod 2: propodus with 3–5 RS on palm. Pereopod 3: propodus with 4 RS on palm. Pereopod 7: basis of medium breadth, width 0.49× length; distance between anterior margin and medial carina less than between posterior margin and medial carina; posterior margin with setae along entire length. Penes: present. Pleopod 2 appendix masculina: extending subequal with tip of endopod or just shorter than endopod, 0.9–1× length of endopod; twisted; broad; apex bent laterally slightly, bluntly rounded. Uropods: exopod subequal to endopod, 1× the length of the endopod.

Sexual dimorphism. Females may be larger than males.

Size. Females to 37 mm, males to 27 mm.

Remarks. Natatolana obtusata and N. nitida are the only species of Natatolana in which males have an excavate medial margin on the endopod of pleopod 2 and a distinctly twisted appendix masculina. Natatolana obtusata most noticeably differs from N. nitida in having the anteroventral corner of coxa 2 rounded, not produced into an acute tooth, and in having the posterodorsal margin of pleonite 4 sinuate, not concave. Natatolana intermedia is also similar but has a concave posterodorsal margin on pleonite 4.

Distribution and ecology. Antarctica: Gauss Station, Posadowsky Bay, 385 m; Visikoi, S. Sandwich 10–17 m;

Bridgeman, S. Sandwich, Antarctic Peninsula, Weddell Sea, 750 m ( Brandt, 1988). Scavenger. The anatomy and ultrastructure of the digestive system of this species has been studied by Storch et al. (2002).