Abstract
The polychaetes of the family Cirratulidae (Annelida) are common inhabitants in offshore benthic sediments and considered as an important group in environmental monitoring. Amongst them, the genus Chaetozone is the most species-diverse worldwide. Seven species of Chaetozone have been recorded in Norway, although these records should be considered cautiously as species delineation is challenging with morphological means. In order to determinate the number of species present in Norway and their distribution, 306 specimens from Norwegian and adjacent waters were DNA sequenced (the universal mitochondrial barcoding region COI, and D1-D2 regions of the nuclear 28S rDNA) and datasets investigated after phylogenetic and species delimitation analyses such as ABGD, mPTP and GMYC. These molecular analyses were used as a frame to re-examine the morphological diagnostic features of each of the species.
Over 130 new COI barcodes are obtained, and a total of 16 species are recovered in the analyses. This includes sequences from specimens of the type locality of the type species of the genus, Chaetozone setosa, and its distribution was confirmed to be limited (in Norway) to Arctic waters. The morphology and nomenclature of all species are discussed.
This is a first molecular approach to resolve the species delineation, evolutionary relationships and geographic structure of members of Chaetozone, a genus which taxonomy has proven to be difficult. It provides a tool for both molecular and morphological identification and demonstrates the considerable underestimation of the diversity of Chaetozone, in the North East Atlantic. This also gives a taste of what is to be expected for the rest of the elusive systematics of the family Cirratulidae.
