New species of Laetmonice (Aphroditidae, Annelida) from bathyal and abyssal depths around Australia

Research voyages on board RV ‘Investigator’ between 2015 and 2022 sampled benthic communities of Australia’s Eastern and Southern continental margins from the slope down to abyssal depths (463–5000 m) as well as the seamounts off the Indian Ocean Australian Territories (IOT) that include Christmas Island and Cocos (Keeling) Islands. Over 500 specimens of the annelid family Aphroditidae were collected during the voyages. Some of the most common aphroditids collected during these voyages belonged to the large-bodied members of the genus Laetmonice. We used fragments of COI and 16S genes to investigate the diversity of the genus. Phylogenetic studies revealed the presence of at least nine distinct mitochondrial genetic lineages within Laetmonice, four of which have been described here as Laetmonice hutchingsae sp. nov., L. murrayae sp. nov., L. mensahaedorum sp. nov. and L. paxtonae sp. nov. The new taxa are clearly structured by their bathymetric distributions. These results argue against eurybathic distribution within the genus Laetmonice and demonstrate the existence of genetically divergent taxa isolated by bathymetric environmental gradients.