New bathyal amphipod species (Amphipoda: Eusiridae: Rhachotropis) from southwestern Pacific through integrative taxonomy

Within the hyper-diverse group of the amphipods, little is known about deep-sea benthic species that still represent an unknown reservoir of species to be discovered, particularly in remote regions of the southwestern Pacific. Herein, we are describing three new deep-sea species of Rhachotropis from Papua New Guinea, Solomon archipelago, and Vanuatu using an integrative taxonomy approach, combining morphological and molecular characters with biological and ecological information. Nomenclatural comments and a key to Rhachotropis species occurring in the bathyal provinces from the southwestern Pacific are also provided. Comments on the sex ratio and fecundity of the genus are also discussed. The biogeography and distribution of the newly described species as well as congeneric species occurring in the area are discussed, and new DNA data are shedding new light on the global phylogenetic relationships (geography, depth range) of the deep-sea genus Rhachotropis.