Cardiosporidium

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There is one known species in this genus: Cardiosporidium cionae. It appears to be related to the genera Babesia, Cytauxzoon and Theileria.

The parasite infects the pericardial body of the host. Like other members of this phylum it possesses apicoplasts, rhoptry and subpellicular microtubules. This Apicomplexan parasite is occasionally itself "parasitised" by an alphaproteobacteria from the order Rickettsiales. The symbiont is termed a "parasite" only as a shorthand convenience. Technically speaking, it may actually act more as a mutualist-symbiont or a commensal-symbiont rather than a parasitic-symbiont. It synthesizes the essential metabolites lysine and lipoic acid, which likely benefits the holobiont: These apicomplexan hosts bearing this endo-symbiotic bacterium may benefit from the supply of extra nutrients. A similar apicomplexan from the genus Nephromyces has also been described. They are found in Narraganset Bay Rhode Island and in the Gulf of Naples.