A new large predator (Amphipoda, Eusiridae) hidden at hadal depths of the Atacama Trench

Abstract

The deep ocean is a vast reservoir of new species to science, and each discovery improves our ecological understanding of these remote ecosystems. One island-like ecosystem is the Atacama Trench (Southeast Pacific Ocean), where the hadal depths (>6000 m) host a distinctive endemic community. Unlike the communities of other hadal subduction trenches, predatory (non-scavenging) amphipods have not been documented or collected from the Atacama Trench. In this study, we applied an integrative taxonomic approach to describe a new predatory amphipod in the Eusiridae Stebbing, 1888 family collected from 7902 m during the 2023 IDOOS Expedition and provide an updated global Eusiridae key with the 14th genus. Morphology and DNA barcoding robustly supported raising a new genus separate from the systematically similar genera Dorotea. Dulcinea camanchaca gen. nov. sp. nov. is a large amphipod (holotype: 38.9 mm length) with diagnostic features that include: a smooth dorsal body, 12 spines on the outer maxilla 1 plate, subsimilar and strongly subchelate gnathopods with broad carpus lobes, the pereopods 3 and 4 dactyli are 0.45× of the respective propodus and pereopods 5 to 7 dactyli are 0.6×, a distal spiniform process on the peduncle of uropod 1, and an elongated but weakly cleft telson. Together, Dulcinea camanchaca gen. nov. sp. nov. is a novel predator and reinforces the eco-evolutionary distinctiveness of the Atacama Trench. http://zoobank.org/urn:lsid:zoobank.org:pub:95A6C497-AC8E-4C24-B451-C4B7F76CE687.