New Macrostylidae (Isopoda) from the Northwest Pacific Basin described by means of integrative taxonomy with reference to geographic barriers in the abyss. Three new species of Macrostylidae from the Northwest Pacific Basin

During the KuramBio expedition in 2012, previously unknown Macrostylidae (Crustacea, Isopoda) were collected from the Northwest Pacific Basin near the Kuril-Kamchatka Trench. Three of these species are described herein combining morphological and molecular-genetic approaches. The use of Confocal Laser Scanning Microscopy was evaluated and found a valuable, non-destructive method to visualize precious type material as opposed to Scanning Electron Microscopy which renders material useless for other purposes.In the KuramBio samples two species (Macrostylis sabinae n. sp., M. amaliae n. sp.) were numerically dominating this family. Moreover, their females are morphologically indistinguishable and have thus been delineated by means of DNA data. The adult males, however, are distinguishable by their antennula and the type of aesthetascs. This is the first time that a new type of aesthetasc was assigned to this family. For these two species evidence for a sexual size dimorphism, in which the females are significantly larger than the males, was found.M. sabinae n. sp. was widely distributed, so a biogeographic approach was followed and the dispersibility of benthic infaunal isopods across deep-sea trenches in the abyssal deep sea is discussed.