Pseudidothea scutata (Stephensen)

Poore And T, Gary C. B., 2004, Pseudidotheidae (Crustacea: Isopoda: Valvifera) reviewed with description of a new species, first from Australia, Memoirs of Museum Victoria 61 (1), pp. 75-83 : 82-83

Pseudidothea scutata (Stephensen)

Microarcturus scutatus Stephensen, 1947: 15–17 , figs 5, 6. Pseudidothea scutatus Sheppard, 1957: 176–180 , figs 15, 16. Pseudidothea scutatas .— Brandt and Wägele, 1990: 97–105, figs

1–3 (lapsus)

Material examined. Antarctica, Western Weddell Sea , A. Brandt on RV Polarstern, Jan–Feb 2002 ( ANDEEP stns): 61°09.82'S, 54°33.40'W, 302–306 m, NMV J47401 (1 male); 61°11.94'S, 54°37.37'W, 302–306 m, NMV J47402 (1 male); 61°20.51'S, 55°28.66'W, 159– 117 m, NMV J47403 (1 female); 61°44.88'S, 58°1.54'W, 256–295 m, NMV J47404 (1 male); 59°52.21'S, 59°58.75'W), 3643– 3622 m, NMV J47405 (1 specimen) .

Diagnosis. Head smooth, pereonites with large, high, flat tubercles: pereonite 1 with 1 pair of dorsal tubercles and 3 pairs of shorter lateral processes; pereonites 2–4 with 1 pair of dorsal and 1 pair of lateral tubercles and 1 or 2 pairs of shorter dorsolateral processes; pereonites 5–7 with 1 pair each of dorsal, dorsolateral and lateral tubercles. Pleotelson with subacute anterolateral processes, 3 pairs of mediodorsal spines and shorter and more irregular processes, apically acute and bent dorsally. Male antenna 1 flagellum with about 25 clusters of aesthetascs. Antenna 2 and pereopods 2 and 3 with tubercles. Antenna 2 peduncle with long, fine setae on articles 3–5. Male pleopod 1 endopod about as long as peduncle with plumose setae laterally and apically; exopod longer than endopod, with diagonal groove, apically tapering, bent outwards and terminating in an acute tooth, proximal half of lateral margin with short setae, distal half with longer, plumose setae. Male pleopod 2 appendix masculina apically acute, about twice as long as rami ( Stephensen, 1947). Uropodal exopod about two-thirds as long as endopod, each ramus with single seta ( Sheppard, 1957). Oostegite present on pereopod 5.

Distribution. South Shetland Islands, Antarctic Peninsula, 159–3622 m depth.

Remarks. Sheppard (1957) included Stephensen’s Microarcturus scutatus in the synonymy of what she called “ Pseudidothea scutatus sp. n. ”. She admitted that Stephensen’s “species appears to be identical with my specimens” and that she received Stephensen’s paper after making her own descriptions and figures. Her intention would appear to have been be to make a new combination rather than a new species.

The species differs from all other species of Pseudidothea in the presence of well developed oostegites on pereopods 5 (Sheppard’s 1947 observation confirmed in new material). Although the pair of fifth oostegites meet in the middle, they are flat and do not help in enclosing the eggs.

The dorsal and lateral pereonal tubercles of the holotype, a 20-mm long male, are separated by gaps smaller than the tubercle diameters. In the same-sized female described by Brandt and Wägele (1990) the tubercles are relatively smaller and separated by gaps equal to their diameters. The uropodal rami of the two specimens also differ: the endopod of the male being shorter and narrower than the exopod while the two are subequal in the female. In the absence of other material, we assume these differences are sexual rather than specific. The new material collected during the 2002 ANDEEP cruise is typical of this well-described species. The individual dredged from 3643– 3622 m depth, much deeper than the usual depths of a few hundred metres, could not be distinguished from the rest.