Two new species of Atopobathynella (Parabathynellidae, Bathynellacea) from the Pilbara region, Australia

Abstract

Fifteen species of the Gondwanan genus Atopobathynella have been described so far from four countries. The position of the genus within the family Parabathynellidae and its species relationships are controversial due to the different characters and species considered by different authors, however most of the phylogenetic reconstructions are based solely on morphological characters. In the past few decades, the arid zones of Western Australia, including the Pilbara region, have been recognized as a hotspot for subterranean fauna. Material is constantly collected to produce Environmental Impact Assessments to protect and manage the subterranean environment. In 2009 the Cleaverville Iron Formation, in the Pilbara region, northern Western Australia, was proposed to be mined, therefore subterranean fauna sampling was conducted as per legislation. Preliminary molecular studies of stygofauna identified two distinct Parabathynellidae lineages from two ridges, however no morphological descriptions were carried out at that time. In this study, we describe two new species from Yarrie and Callawa ridges, respectively: Atopobathynella yarriensis sp. nov. and A. degreyensis sp. nov.. The new species show differences in male antennal organ, ventral tooth of mandible, number of teeth on distal endite of maxillula, absence or presence of epipod of thoracopod I, number of setae on article 4 of thoracopod II, length of distal external seta of exopod of all thoracopods, outer lobe of male thoracopod VIII, number of spines on uropodal sympod and furcal rami, length of the external dorsal plumose seta of the furcal rami. Additionally, we integrated the morphological data with sequences of three genetic loci, Cytochrome Oxidase c Subunit I (COI), 12S rRNA (12S), and nuclear 18S rRNA (18S), calculating p-distances and constructing a multigene molecular phylogeny to support morphology, and explore the monophyletic status of the genus and the relationship amongst its species. The two new species were well supported in our phylogeny, however they appear distantly related.