Use of the Pacific oyster (Magallana gigas) as a natural sampler for the detection of Neoparamoeba perurans

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 complimenting gill scoring and histology methods for AGD assessment. Molecular detection depends on reliable and simple sample collection, opening the possibility of using natural samplers (organisms that collect/accumulate DNA through feeding/foraging) for aquatic eDNA collection. 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 eDNA samplers for N. perurans, providing a useful, simplified collection method.