DAO prepress abstract  -  DOI: https://doi.org/10.3354/dao03175

Partial 18S rRNA sequences of Apicomplexan parasite 'X' (APX), associated with flat oysters Ostrea chilensis in New Zealand

Nguyen Thao Suong*, Stephen Webb, Jonathan Banks, Kevin C. Wakeman, Henry Lane, Andrew Jeffs, Cara Brosnahan, Brian Jones, Andrew Fidler

*Email: sngu189@aucklanduni.ac.nz

ABSTRACT: Apicomplexa is a large phylum of parasitic protists renowned for significant negative health impacts on humans and livestock health around the world. Despite the prevalence and negative impacts of apicomplexans across many metazoan (animal) groups, relatively little attention has been given to apicomplexan parasites of invertebrates, especially marine invertebrates. Previous work has reported an apicomplexan parasite – “X” (APX), a parasite that has been histologically and ultrastructurally identified from the commercially important flat oyster (Ostrea chilensis) in New Zealand. This apicomplexan may exacerbate host vulnerability to the infectious disease bonamiosis. In this study, we report 18S rRNA sequences amplified from APX infected O. chilensis tissues. Phylogenetic analyses clearly established that the 18S sequences were of apicomplexan origin, however, their detailed relationship to known apicomplexan groups is less resolved. Two specific probes, designed from the putative APX 18S rRNA sequence, co-localised with APX cells in in situ hybridisations, further supporting our hypothesis that the 18S sequences were from APX. These sequences will facilitate the future development of inexpensive and sensitive molecular diagnostic tests for APX thereby facilitating research focused on the biology and ecology of this organism and its role in morbidity and mortality of O. chilensis.