Perkinsus olseni and other parasites and abnormal tissue structures in New Zealand Greenshell™ mussels (Perna canaliculus) across different seasons

Abstract The New Zealand Greenshell™ mussel ( Perna canaliculus ) supports the largest aquaculture industry in country. However, summer mortality events and potential disease outbreaks may threaten growth of this industry. As an approach to gauging threats through seasons, a detailed histopathological examination was conducted on 256 adult cultured mussels collected from farm between April 2018 September 2019, which covered austral autumn, winter, spring seasons. Histological sections followed by confirmatory situ hybridization (ISH) resulted identification Perkinsus olseni at overall prevalence 56%. Other parasites pathogens were identified histology: apicomplexan parasite X (APX) (78%), copepods Pseudomyicola spinosus or Lichomolgus uncus (1%), Microsporidium rapuae intracellular microcolonies bacteria (IMCs) (2%) bacilli cocci (4%) gills, mantle, gonads, digestive epithelium tubules. There significant association P. APX infection mussels. This is first report seasonal variations mussel. seasons presence A positive brown material accumulation APX) haemocytosis infections recorded. health condition (healthy unhealthy) observed. Moreover, tubule deterioration (large lumen, with thin epithelial wall) noted. Therefore, study provides information regarding for time , their host-parasite interactions within commercial farm.