The myxospore is released from the fish host. It has a pair of polar capsules, each formed by a separate cell. It has a binucleate sporoplasm which is inoculated into the aquatic annelid host.
The actinospore, also known as a triactinomyxon (TAM) is released from the aquaticannelid host. It has three polar capsules, and a multinucleate sporoplasm, which is inoculated into the fish host.