Paralytic Shellfish Toxin accumulation in fast growing oysters

Phycotoxins can be accumulated by shellfish during harmful algal blooms, which then become unsafe for human consumption, resulting in shellfish harvesting closures that can strongly impact the aquaculture industry. Therefore,... [ view full abstract ]

Phycotoxins can be accumulated by shellfish during harmful algal blooms, which then become unsafe for human consumption, resulting in shellfish harvesting closures that can strongly impact the aquaculture industry. Therefore, understanding the factors influencing toxin accumulation in shellfish is an important public-health and socio-economical challenge.
Although ploidy modification and selective breeding are widely used in the oyster industry to obtain better performances, it is still unclear how the associated genetic and physiological characteristics can affect toxin accumulation in oyster tissues.

We compared paralytic shellfish toxin (PST) accumulation and profiles in triploid vs. diploid Pacific oysters Crassostrea gigas, and in Sydney Rock oysters Saccostrea glomerata selected for disease resistance and faster growth vs. wild Sydney Rock oysters, after experimental exposure to Alexandrium minutum at field-realistic concentrations.
Results indicate that triploid Pacific oysters accumulated twice as much PSTs than diploids after 4 days of exposure to A. minutum as well as after 7 days of depuration. On the contrary, the selectively bred Sydney Rock oyster lines were not more toxic than the wild type. However, the PST profiles of fast growing oysters suggest differential metabolization of certain PST analogues, which may be due to different metabolic activities.

As a conclusion, triploid Pacific oysters and certain lines of Sydney Rock oysters may present a higher risk during a bloom of PST-producing phytoplankton.