The Pacific Oyster ( <i>Magallana gigas</i> ) as a Potential Natural Sampler for <i>Neoparamoeba perurans</i> Detection

Amoebic gill disease (AGD), caused by Neoparamoeba perurans , is a challenge for Atlantic salmon aquaculture. Research has, therefore, focused on detecting/monitoring N. perurans loads within/around fish pens. Recently, molecular methods to detect N. perurans have been used to reduce labour‐intensive sampling, inconsistency, and stress on stock while complementing gill scoring and histology methods for AGD assessment. Molecular detection depends on reliable and cost‐effective sample collection. Recent studies have demonstrated the potential for utilising naturally occurring filter‐feeding animals as a mechanism for collecting DNA from the environment (i.e., ‘natural samplers’) for use in downstream molecular assays. This opens the possibility of sampling with minimal training or expertise, offering the potential to easily integrate this sampling within normal farm operations. We evaluated, through aquarium‐based experiments, the utility of the Pacific oyster ( Magallana gigas ) to collect N. perurans DNA from the water column. In aquaria inoculated with N. perurans , total water column amoeba load decreased significantly over time in the presence of oysters. Despite this decrease, no correlation between the level of amoeba accumulation within oysters and the decrease in the water column was observed. N. perurans was detected in every oyster organ type tested (mantle, gill, palp, and digestive gland), though with high variation. The detection of N. perurans DNA within the digestive gland indicates that oysters ingested amoeba. Oysters were found to be viable environmental DNA (eDNA) samplers for N. perurans , providing a useful collection method.