Amazing diversity of Nothria (Annelida, Onuphidae) in the Australian deep sea

The epibenthic onuphid genus Nothria Malmgren, 1867 presently comprises 21 accepted species. We are reporting here on specimens collected during six deep-sea expeditions of the RV Investigator from 2015–2018 to the Great Australian Bight (GAB) and off eastern Australia from Tasmania to Queensland, describing eight new species of Nothria. This is the first integrated study of the genus, sequencing the markers COI, 16S rDNA and 28S rDNA from 37 specimens and employing conventional and exploratory morphological characters as well as tube consistency and structure for identification. Molecular data provided strong support for recognition of the eight new species and the Nothria otsuchiensis Imajima, 1986 species complex. Since the analysis of morphology between the specimens of this complex has not revealed any obvious differences, it may represent a complex of cryptic species. Nothria digitata sp. nov. was collected at a depth of 400 m whilst the remaining seven new species are from depths of 980–2751 m. Nothria deltasigma sp. nov., N. digitata sp. nov. and N. minima sp. nov. were collected at a single station each, while N. josae sp. nov. and N. simplex sp. nov. were found at two stations. However, N. delta sp. nov. displayed the widest distribution, occurring at GAB, Tasmania and Jervis Bay Marine Park, NSW. Most stations yielded only one species, Jervis Bay Marine Park and south of Brians, Tasmania, harboured two, but an astounding example of sympatry was discovered at Huon Marine Park, Tasmania, where three species, N. delta sp. nov., N. lizae sp. nov. and N. orensanzi sp. nov. were collected together in one station.