Shallow-water Asellota (Isopoda) from the Beagle Channel: an approach to diversity and faunistic affinities.

DOTI, B.L.; ROCCATAGLIATA, D.; ZELAYA, D.G.

Ushuaia

Simposio; IBMANT/ANDEEP International Symposium and Workshop, 2003; 2003

CADIC, Alfred Wegener Institut (AWI), Hamburg University

The shallow-water Asellota from the Beagle Channel are poorly known, with only six species previously recorded. In order to increase our knowledge of this faunule four localities along the Beagle Channel were sampled between 2001-2002. The material studied was collected with a small dredge on Gable Island, Moat Mount, San Pío Cape and  Sloggett Bay, at 30 m depth. Among the 3,085 specimens sorted, 23 species and 2 “species complex” were identified. These species belong to the following six families: Paramunnidae, Janiridae, Joeropsidae, Munnidae, Acanthaspidiidae and Santiidae. The Paramunnidae showed the highest diversity and abundance (Fig. 1). The species included in this family belong to the following genera: Allorostrata (2 species), Antennulosignum (1 species), Austrosignum (2 species), Paramunna (4 species, 1 “species complex”) and Pleurosignum (1 species). Until now, Allorostrata was only known for a single species from the Magellan Strait; a second species of this genus is reported in the present study. Additional specimens of Antennulosignum, a genus only known for a single species from the Malvinas Islands, is herein mentioned for the Beagle Channel. For Austrosignum two new species are reported. The Paramunna material contains four distinctive species as well as many specimens of questionable taxonomic position, some of which are provisionally identified as P. kerguelensis and P. menziesi. The Janiridae comprises the genera Austrofilius (2 species), Caecianiropsis (1 species), Ianiropsis (2 species), Notasellus (1 species)  and Neojaera (1 species). For the genus Caecianiropsis the first record for the Magellan Region is provided. The remaining four families, Joeropsidae, Munnidae, Acanthaspidiidae and Santiidae, are represented each by a single genus: Joeropsis (3 species), Munna (1 species, 1 “species complex”), Ianthopsis (1 species) and Santia (1 species), respectively. After combining our data and those compiled from literature the following biogeographic patterns arise: (1) The Beagle Channel and the Magellan Strait have the same number of shallow-water Asellota (<100 m depth): for each area 28 species have been recorded; (2) In both areas the family Paramunnidae totals almost half of the Asellota; (3) Besides being well represented in the Magellan Region (39.1% of the Asellota reported), the Paramunnidae is also common in the Antarctic Peninsula and Weddell Sea (32.3%), but remarkably scarce in the Scotia Arc Islands (13.8%). Further samples are required to confirm if the low number of Paramunnidae known from the Scotia Arc is a reliable figure.