Physiological Impacts of a Newly Discovered Trematode Parasite on Its Host, the Bay Scallop (Argopecten irradians)

Parasites have the potential to impact aquaculture by degrading product quality, increasing mortality, and reducing fecundity. Previous research has identified a novel trematode parasite, Saccularina sp., infecting the gills of wild and cultured populations of bay scallops, Argopecten irradians, that inhabit the North Carolina coast and the Gulf Coast of Florida. However, the physiological impacts of Saccularina sp. on its scallop host are currently unknown. We quantified the effects of Saccularina sp. infection on clearance rate (an indicator of feeding potential), condition, and reproduction. Visually (to the naked eye) infected bay scallops exhibited lower clearance rates, had smaller muscle and gonad weights relative to shell size, and showed reduced fecundity compared to their visually uninfected counterparts. However, when scallops spawned successfully, there was no significant difference between visually infected and visually uninfected scallops in the proportion of embryos developing into D-stage larvae. Overall, this study shows that Saccularina sp. reduces the metabolic energy available to A. irradians, resulting in decreased size, meat yield, and fecundity, with negative implications for aquaculture and presently-depleted wild populations of bay scallops.