Microcell parasites of oysters: Recent insights and future trends

Our understanding of the microcell oyster parasites of the genera Bonamia and Mikrocwos has expanded 111 recent years with the application of ultrastru ctural and espec ially molecular biological research approaches. Molecular phylogenetic analyses of SSU rRNA genes have united three species, Bonamia ostreae, Bonamia exitiosa, and Mikrocytos (now Bonamia) roughleyi, in a microcell clade within the Haplosporidia, supporting both early and recent ultrastructural observations. Ult rastructural and molecular phylogenetic ev idence has emerged that Mikrocytos mackini, on the other hand, is a unique proti st with unusual adaptations for a parasitic existence. DNA probes and polymerase chain reaction (PCR) assays promise new insights into the life cycles, tran smi ssion, and diversity of these organ isms. The development of Ostrea eclulis lines selected for B. ostreae resistance wi ll increase the viability of aquaculture industries for this species and, combined with rapidly developing biotechnological approaches for studying host defenses and host-parasite interactions, will allow greater insight into the nature of phenomena such as resistance and tol erance to disease in oysters