Traditionally, many small-sized copepod species are considered to be widespread, bipolar or cosmopolitan. However, these large-scale distribution patterns need to be re-examined in view of increasing evidence of cryptic and pseudo-cryptic speciation in

The present study investigated whether the cyclopoid copepod Oithona similis Claus 1866 is a cosmopolitan or a conglomerate of cryptic species. Adult and subadult females (C5 stages) of O. similis were closely examined morphologically and via DNA-barcoding

Climate change is likely to have major impacts on global ecosystems, and this is especially the case in the rapidly warming Arctic regions1,2. Warmer sea temperatures and a longer open water season create new opportunities for sub-Arctic and boreal species