Tree inferred using the maximum likelihood method based on the 28S rDNA sequence data; only bootstrap values higher than 70 are indicated. The newly generated sequences of Derogenes varicus sensu stricto from Sweden, Northeast Atlantic are indicated by*. Other D. varicus sensu stricto are those of Krupenko et al. [30] from the Barents Sea and White Sea; and those of Bouguerche et al. [3] from Northeast Atlantic, off Sweden and Norway and from Svalbard, Norway, Arctic Ocean.