Polychaete-parasitizing copepods from the deep-sea Kuril–Kamchatka Trench (Pacific Ocean), with the description of a new Ophelicola species and comments on the currently known annelidicolous copepods

The annelid associated copepods, collectively called annelidicolous, were placed in 21 families. Some genera, such as Ophelicola, are considered phylogenetically isolated and are placed into the order Cyclopoida as incertae sedis. In this paper, we describe Ophelicola kurambia, the second species recorded for the genus and the first for the Pacific Ocean. The single known specimen, a female, was found during the German–Russian deep-sea expedition KuramBio at the deep-sea Kuril–Kamchatka Trench. The new species differs from Ophelicola drachi (known from the Gulf of Biscay, Atlantic Ocean) in being attached to the host through the mandibles instead of maxillae and, specially, in the formula of the antennular armature. The study of the new species contributes to clarify the diagnosis of the genus, which clearly differs from Notomasticola (another incertae sedis genus), and resembles both the most modified clausiids (in the mandibular shape and antennular segmentation) and the clausidiids (in the shape of maxilla). However, it does not contribute to clarify the position of Ophelicola within the order Cyclopoida. The paper includes a list of the known annelidicolous copepods (excluding Monstrilloidae) and summarises the main trends shown in terms of diversity, distribution and relationships. Currently, 168 species of copepods from to 74 genera and 22 families and 7 incertae sedis (excluding Monstrilloida) are known to be involved in 235 parasitic relationships (mostly ectoparasitic) with polychaetes. Host polychaetes include 156 species belonging to 104 genera from 22 families (plus 14 unknown). About 50% of these relationships are known from European waters, mainly from shallow depths.