Taxonomy and species distribution of the genus Manganonema Bussau, 1993 (Nematoda : Monhysterida)

Different deep-sea sites are frequently characterized by a high number of species belonging to the same genus. In addition, some deep-sea genera (e.g. Acantholaimus, Monhystera, Halalaimus) seem to be dominant and present worldwide. The genus Manganonema is present in all oceans in low to medium densities (< 2%) and, apparently, restricted to the deep sea (600 m and deeper). The present study deals with a revision of the genus Manganonema based upon known species and nine new species, where only 5 were named due to the lack of males (M. media sp. nov., M. pitilica sp. nov., M. robustus sp. nov., M. antarctica sp. nov., M. bussauensis sp. nov.). For the species identification, important characters are summarized in a pictorial key. The material studied was collected from six different sites: two in the North Atlantic (Europe), two in the Southern Ocean (Antarctic), one in the South-western Atlantic (Brazil), and one in Western Indian Ocean (Kenya). The species distribution suggests a high turnover of species between sites. Only one Manganonema species is recorded from two different sites in the Atlantic Ocean. These results suggest a high degree of endemism of species within the genus.