Parasites, pathogens, and other symbionts of copepods.

There is a large diversity of eukaryotic symbionts of copepods, dominated by epizootic protists such as ciliates, and metazoan parasites. Eukaryotic endoparasites, copepod-associated bacteria, and viruses are less well known, partly due to technical limitations. However, new molecular techniques, combined with a range of other approaches, provide a complementary toolkit for understanding the complete symbiome of copepods and how the symbiome relates to their ecological roles, relationships with other biota, and responses to environmental change. In this review we provide the most complete overview of the copepod symbiome to date, including microeukaryotes, metazoan parasites, bacteria, and viruses, and provide extensive literature databases to inform future studies. Copepods are vectors of pathogens of other aquatic organisms, including commercially harvested species and those used for aquaculture. Extensive supplementary materials are provided, referencing copepod-associated eukaryotes, bacteria, and viruses. Phylogenetic analyses of dinoflagellate and microsporidian parasites of copepods show a wide phylogenetic distribution of parasitic lineages, with some copepod-infecting specialists and evolutionary radiations. The review provides an overview of recent high-throughput sequencing (microbiome, symbiome) studies of copepods and their physiological implications for marine ecosystems. Synthesizing the relationship between host, environment, and symbiome/pathobiome is important for understanding copepod health and population dynamics, and also the contribution of the copepod holobiont to biogeochemical cycling. [ABSTRACT FROM AUTHOR]