Mikrocytids Are a Broadly Distributed and Divergent Radiation of Parasites in Aquatic Invertebrates

• Published in: Current biology 2014-03, Vol.24 (7), p.807-812
• Main Authors: Hartikainen, Hanna, Stentiford, Grant D., Bateman, Kelly S., Berney, Cédric, Feist, Stephen W., Longshaw, Matt, Okamura, Beth, Stone, David, Ward, Georgia, Wood, Charlotte, Bass, David
• Format: Article
• Language: English
• Subjects: Animals; Aquaculture; Brachyura - parasitology; Decapoda; Genes, Protozoan; Introduced Species; Invertebrata; Mikrocytos; Mikrocytos mackini; Molecular Sequence Data; Ostreidae - parasitology; Phylogeny; Rhizaria - classification; Rhizaria - genetics; Rhizaria - isolation & purification; United Kingdom
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2014.02.033

Microcell parasites have independently evolved in several eukaryotic lineages and are increasingly recognized as important and emerging pathogens of diverse hosts, including species of economic importance subject to international legislation concerning the trading of aquatic animals [1–3]. The microcell Mikrocytos mackini causes Denman Island disease of oysters and represents one of the most genetically divergent eukaryotes known. Mikrocytos has remained an isolated lineage with a limited distribution. We investigated two emerging diseases of juvenile crabs and oysters from the UK using massively parallel sequencing and targeted primer approaches to reveal that their causative agents are highly divergent lineages related to M. mackini (Paramikrocytos canceri n. gen. et n. sp. and M. mimicus sp. nov., respectively). We demonstrate a major new globally distributed parasite radiation (Mikrocytida ord. nov.) with phylogenetic affinities to the commercially important haplosporidian parasites of invertebrates. Mikrocytids have eluded detection because of their small size, intracellular habit, and extreme sequence divergence. P. canceri was frequently detected in a range of shoreline invertebrates, demonstrating that these newly recognized parasites are in fact common, diverse, and widespread and should be considered when assessing the risks of aquaculture activities, invasive species spread, and movements of ballast water and sediments with associated invertebrates. [Display omitted] •Mikrocytids are some of the most divergent eukaryotes known•Mikrocytids are endoparasites of mollusk, crustacean, and possibly annelid hosts•Mikrocytids occur in marine, brackish, and freshwater habitats•Mikrocytids are sister to the haplosporidians in the supergroup Rhizaria Hartikainen et al. reveal previously unknown diversity in a highly divergent lineage of Rhizarian protists infecting farmed and wild aquatic invertebrates. Environmental sampling, ground-truthed with traditional approaches to disease investigation, demonstrates how the Mikrocytida occur widely in fresh, brackish, and marine waters around the globe.