Rectarcturus kophameli

Rectarcturus kophameli (Ohlin, 1901)

Arcturus kophameli Ohlin, 1901: 272–273, fig. 5.

Antarcturus kophameli. – Stebbing, 1908: 53.

Microarcturus kophameli. – Nordenstam, 1933: 128.

Rectarcturus kophameli. – Schultz, 1981: 68, fig. 3A–G. – Park and Wägele, 1995: 71–75, figs 9–12. – Poore, 2003: 1843.

Types. Northern Argentina, 38°S, 56°W, 52 fm [95 m] depth, holotype, female, 11 mm, lost.

Material examined. Argentina, Beagle Channel (55°S, 68°W, 63 m, Nov 1994, A. Brandt (Victor Hansen stn 1213), NMV J47040 (two specimens).

Description. Male. Pereonites 2–4 swollen, taller and broader than more anterior and posterior segments, sparsely and microscopically pustulose between transverse ridges, 3 times as long as greatest width. Pleotelson 0.3 times total body length. Head with 2 pairs of broad, blunt submedian tubercles, followed by single medial tubercle.

Antennule flagellum article 1 with 3 pairs plus 1 aesthetascs, article 2 with 2 aesthetascs. Antenna, fused articles (1 + 2) short, stout, with ventrolateral flange; article 5 0.5 times length of article 4; flagellum of 3 articles, 0.7 times length of peduncle article 5.

Pereopod 1 propodus 1.9 times as long as wide. Pereopod 2 with tubercle on extensor margin of basis only; dactylus unguis 0.9 times length of dactylus body. Pereopod 4 dactylus body 0.9 times as long as propodus, unguis setiform, 0.4 times length of dactylus body. Pereopods 5–7 without tubercles on extensor margin. Pereopod 7 dactylus body 0.7 times as long as propodus, unguis stout, 0.4 times length of dactylus body.

Male pleopod 1 exopod more than 4 times as long as basal width; posterior face without erect lobes along groove; distomesial seta-bearing lamina well separated from apex by deep triangular notch and equalling it in length.

Uropodal exopod 0.5 times length of endopod.

Ovigerous female. See detailed description by Park and Wägele (1995). Oostegites 5 absent.

Distribution. Northern Argentina, 38°S, 95 m (type locality); Straits of Magellan, Argentina, 52°S, 10–12 m depth.

Remarks. Ohlin (1901) based his new species on an ovigerous female from off northern Argentina at 95 m depth. Schultz (1981) selected this as the type species of his new genus and redescribed it on the basis of new material, ovigerous females from off Isla de los Estados, southern Argentina, at 84–208 m depth. The holotype appears lost; it could not be found in the major museums in Stockholm, Hamburg or Berlin. Other authors transferred the species to other genera, Antarcturus and the nomen nudum, Microarcturus. The species is characterised by sharp submedian, sublateral and lateral longitudinal ridges on each pereonite, and sublateral ridges on pleonites 1 and 2. The lateral mid-length pleotelson marginal wings are weak. Ohlin commented on the ‘very small hairs’ over the whole body. Park and Wägele (1995) redescribed new material, taken at shallower depths in the Straits of Magellan, Argentina than the type locality. Their observations were confirmed by additional material from the same region (representatives of a larger collection at the Zoological Museum, Hamburg). W. Wägele (pers. comm.) observed the absence of oostegites 5 on the female described by Park and Wägele (1995) and now at Zoologisches Forschungsmuseum Alexander Koenig, Bonn, Germany.