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Abstract

Two new species of desmosomatid isopods, Eugerdella margaretae sp. n. and Eugerdella celata sp. n. are described from Admiralty Bay, King George Island, South Shetlands. Information is added to the original description of Eugerdella falklandica (Nordenstam, 1933) based on re−examination of the holotype. Both new species are similar to E. falklandica, for example by the body shape, the shape of pleotelson and presence of rows of four horn−like spines on the head. They are distinguished from E. falklandica by the number of setae on pereopod articles. Eugerdella celata sp. n. is distinguished by the presence of ventral spines on pereonites 1–4
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Abstract

The eurybathic isopod species Chelator insignis shows a wide distribution south of Iceland. We analysed 51 specimens from shelf (213–305 m depth), slope (885–891 m and 1380–1390 m depth) and deep−sea habitats (2750 m) south of Iceland with different DNA markers. A fragment of the mitochondrial cytochrome c oxidase subunit I gene (COI) was studied for 47 specimens, 16S was studied for 36 specimens, and a fragment for the 18S rRNA gene could be amplified for 11 specimens. For the COI data, specimens clustered into five distinct lineages each separated by ³ 20% uncorrected pairwise distances. Both the mitochondrial 16S and the nuclear 18S sequence data further support this deep divergence, suggesting the presence of overlooked species inside the nominal C. insignis . Populations on the shelf occurring east and west of the Reykjanes Ridge were genetically identical suggesting that this ridge is not a barrier to gene flow. However, populations from different depth ranges differed substantially. Our multi−gene analysis suggests that the newly found species likely have more narrow vertical distribution ranges and highlights a possible role of bathymetry in speciation processes.
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