Cryptic speciation in the giant Antarctic isopod Glyptonotus antarcticus (Isopoda, Valvifera, Chaetiliidae)

The genus Glyptonotus is most commonly regarded as monospecific, with Glyptonotus antarcticus Eights 1852 being its only constituent. Two more forms (G. acutus, G. antarcticus var. obtusus) that had been described based on morphological evidence have received little attention in the literature, though no formal attempt to evaluate their taxonomic status has been undertaken. In a survey of within-species genetic diversity, 23 specimens of the benthic Antarctic isopod Glyptonotus antarcticus from three sampling areas around the Antarctic had a high genetic variability in their mitochondrial LSU (16S) gene. Eleven unique mitochondrial haplotypes were found, two at the Antarctic Peninsula (AP), two in the Ross Sea (RS) and seven in the Eastern Weddell Sea (EWS). Average haplotype variation within sampling areas (AP, RS, EWS) was one order of magnitude less than between sampling areas. In the EWS, however, two highly differentiated haplotypes co-exist. These four groups of haplotypes may represent cryptic, but reproductively isolated species rather than a single species. En una investigación sobre diversidad genética intra-específica se registró variabilidad en el gen mitocondrial LSU (16S) de 23 especímenes del isópodo bentónico antártico Glyptonotus antarcticus de tres áreas antárticas. Se encontraron once haplotipos mitocondriales únicos, dos en la Península Antártica (AP), dos en el Mar de Ross (RS) y siete en el Mar de Weddell (EWS). La variación media de los haplotipos dentro de las áreas (AP, RS, EWS) fue un orden de magnitud menor que entre ellas. Sin embargo, en el EWS coexisten dos haplotipos altamente diferenciados. Estos cuatro grupos de haplotipos pueden representar especies crípticas reproductivamente aisladas, más que una única especie como se asumía anteriormente.