Two new deep-water species of Ampharetidae (Annelida: Polychaeta) from the eastern Australian continental margin

Two new species, Melinnopsis gardelli sp. nov. and Melinnopsis chadwicki sp. nov. (Annelida, Ampharetidae, Melinninae), are described from deep waters off the east coast of Australia. One hundred and 11 specimens were collected during RV Investigator voyage IN2017_V03 in May–June 2017 using a beam trawl at lower bathyal depths (1000–2500 m). This is the first record of Melinnopsis from the eastern Australian coast. The two new species are morphologically similar, but differ by methyl blue staining pattern, shape of thoracic uncini and pigmented glandular bands above the nuchal slits. Melinnopsis gardelli sp. nov. has a conspicuous stained band on the dorsum ending between chaetigers 9 and 10, uncini with three teeth above the rostral tooth and lacks glandular bands, while M. chadwicki sp. nov. has a faint stained band on the dorsum ending at chaetiger 5, uncini with two teeth above the rostral tooth and possesses glandular bands. They also show differences in bathymetric distribution as M. gardelli sp. nov. was collected around 2500 m and M. chadwicki sp. nov. around 1000 m depth. Phylogenetic relationships among the new species and other members of the family Ampharetidae were assessed using the nuclear 18S and the mitochondrial 16S and cytochrome oxidase subunit I (COI) gene fragments. The results revealed that M. gardelli sp. nov. and M. chadwicki sp. nov. form a monophyletic clade and are genetically distinct from each other and all other analysed species. This is the first time molecular data have been used to describe a species in the genus Melinnopsis.