Morphological and molecular characterisation of cardiovascular flukes (Digenea: Spirorchiidae) from marine turtles in Moreton Bay, Queensland.

Spirorchiid flukes inhabit the cardiovascular systems of endangered marine turtles and contribute to strandings and mortalities worldwide. Few studies have explored spirorchiid species assemblages, host-parasite relationships and species-specific pathogenicity. Spirorchiid eggs, rather than adults, are the cause of most significant pathology. Morphological identification of eggs beyond genus level is generally not possible due to inherent similarities, therefore it is difficult to attribute pathogenic effects of eggs to a particular species. This study aims to expand the currently very limited genetic database for spirorchiids to provide a means for identifying spirorchiid eggs to species level. This in turn allows the proper investigation of relative pathogenicity of individual species, leading to development of targeted diagnostics for surveillance and control purposes, as well as improving understanding of spirorchiid diversity and host-parasite relationships in Queensland. Stranded or recently deceased turtles were obtained from government or rehabilitation organisations and adult flukes and eggs collected during detailed necropsies. Adult flukes were stained and mounted for morphological identification after initial examination and categorisation. Portions of adult worms were removed to provide genetic material prior to staining, or additional corresponding whole adults were used. The 28S (partial) and ITS2 nuclear ribosomal genes were amplified by PCR using custom primers and sequenced. The resulting sequences, once matched to morphological identifications and sequences stored in Genbank (where available), were then matched with sequences obtained from eggs to determine species and subsequently identify relationships between species and significant pathology. It is envisioned that the results of this study will lead to the development of a diagnostic test for the surveillance of pathogenic spirorchiids in endangered marine turtles in the Moreton Bay region.