Dubinectes Malyutina & Brandt, 2006

Malyutina, Marina & Brandt, Angelika, 2011, Dubinectes infirmus, a new species of deep-water Munnopsidae (Crustacea, Isopoda, Asellota) from the Argentine Basin, South Atlantic Ocean, ZooKeys 144, pp. 1-19 : 2-3

Genus Dubinectes Malyutina & Brandt, 2006

Dubinectes Malyutina & Brandt, 2006: 4.

Composition.

Dubinectes acutitelson (Menzies, 1962) type species; Dubinectes nodosus (Menzies, 1962); Dubinectes acutirostrum Malyutina & Brandt, 2006; Dubinectes intermedius Malyutina & Brandt, 2006; Dubinectes infirmus sp. n.

Key to the species of Dubinectes (see Fig. 1).

Modified generic diagnosis.

Pleotelson posterior margin surrounded with rim, running perpendicular to margin. Uropod protopod bent at midlength, both margins angled: concave lateral inflexion and projected medial corner, bearing long setae. Body deepest at head. Rostrum of head longer than antennula article 1, with 2 robust distal setae. Distomedial lobe of antennula article 1 reduced, shorter than distolateral projection. Head and pereonites 1-4 subequal in width, pereonite 1 longest, pereonite 4 nearly third of length of pereonite 1, pereonite 7 not longer than pereonite 6. Mandible with high sharp ridge between short spine row and broad molar; condyle longer than molar. Pereopods 1-4 subequal in length. Male pleopod 1 distolateral and distomedial lobes well separated from each other by broad notch, distolateral lobes produced, not narrower than distomedial lobes. Male pleopod 2 protopod distal margin truncated; exopod inserting close to distal margin and emerging posteriorly; endopod basal article twice as broad as stylet; stylet subequal or longer than protopod.

Remarks.

Before finding the Dubinectes infirmus sp. n.the key characters which helped to easily determine known species of Dubinectes without dissection were the strongly calcified integument of the body and the special shape of the pleotelson rim which is well projected ventrally and rises over the dorsal surface. These external features are only weakly pronounced in the new species.Nevertheless, it possesses these characters as well as the main set of diagnostic characters of Dubinectes . The new species has a rim of a pleotelson even if it is narrow, a rostrum which is longer than antennula article 1, a reduced distomedial lobe of the antennula article 1. The head and the ambulosome of the new species are of equal width, the pereonites are progressively shorter from 1 to 4; the coxa of pereopod 4 is broadest in lateral view; the mandible possesses a high sharp ridge between a short spine row and a broad molar; the condyle is longer than the molar; the distal margin of the male pleopod 2 protopod is truncated and the exopod is inserted close to the distal margin and emerged posteriorly. There are some characters which differ the new species from others. These are the shape of the distal margin of male pleopod 1, the length of the stylet of male pleopod 2, the length of the antennula article 3 as well as the length of uropod exopod. These characters in different states were suggested earlier as generic, but seem to bejust specific characters. Therefore, the description of Dubinectes infirmus sp. n. allows to revise the diagnosis of the genus.

Distribution of the genus Dubinectes (Fig.10).

The genus Dubinectes occurs in the Southern hemisphere only in the South Atlantic Ocean. Species of the genus were known from the southeast Atlantic and the Weddell Sea, Southern Ocean, from depths ranging between 1121 and 4960 m. New records the DIVA 3 expedition from the abyss of the Argentine Basin expand the geographical range for the genus to the southwest Atlantic until 27° S latitude in the north. Geographically, Dubinectes nodosus is the most widely distributed species of the genus. It is most eurybathic and has been sampled between 1121 to 4976 m. It was collected in the Weddell Sea at almost every station during the ANDEEP expeditions ( Malyutina and Brandt 2007), but it was much less abundant in the DIVA collections. All other species were recorded only from abyssal depths between 4586 to 4976 m. Dubinectes acutirostrum and Dubinectes infirmus sp. n. are known only from their type localities.