PARALYTIC SHELLFISH POISONING TOXIN ACCUMULATION IN THE ABALONE HALIOTIS MIDAE

Paralytic shellfish poisoning (PSP) is a foodborne illness associated with the consumption of seafood products contaminated with the neurotoxins known collectively as saxitoxins (STXs). Much is known about the toxin sources,... [ view full abstract ]

Paralytic shellfish poisoning (PSP) is a foodborne illness associated with the consumption of seafood products contaminated with the neurotoxins known collectively as saxitoxins (STXs). Much is known about the toxin sources, primarily certain dinoflagellate species, and there is extensive information on toxin transfer to filter-feeding molluscan bivalves, known as the traditional vectors of these toxins. However considerable uncertainty exists as to the source and transfer of these toxins in non-traditional vectors such as abalone. Saxitoxins in the South African abalone Haliotis midae were first detected in 1999 and linked to the presence of the dinoflagellate Alexandrium catenella. Our study aimed to reassess the presence and seasonality of saxitoxins in farmed and wild abalone on the South African coast, to further investigate the anatomical distribution of toxins and to establish rates of depuration of toxins from abalone. Results show toxins to be more prevalent in both farmed and wild abalone to the west of Cape Point (34°21'19.40"S, 18°29'34.64"E) with no indication of seasonal variability. Toxins were found predominantly in the epipodial fringe and to a lesser extent in the muscle and viscera. Abalone size classes showed no significant difference in toxin content. Depuration experiments run over 6 months showed significant fluctuations in toxin concentrations without significant depuration. These fluctuations in the absence of Alexandrium catenella indicate an alternate source of toxin. Future research will investigate cellular localization of the toxins, and bacteria as a possible source of toxins in abalone.