Depuration and transformation of PSP toxins in the South African abalone Haliotis midae

Abstract

Abalone were grown: on diets of 1) artificial feed, 2) kelp, their in situ food source, which contained saxitoxin (STX) derivatives, and 3) in filtered seawater without a food source, to investigate the depuration and transformation of toxins under feeding and starving conditions. The abalone were toxic at the start of each treatment (~160 µg STX eq 100 g-1 tissue). They depurated at a rate of 6.27 µg STX eq 100 g-1 tissue d-1 over the 2 week incubation period when fed artificial feed; however, no depuration was observed in starved or kelp-fed animals. Toxin transformations occurred in abalone for each treatment. Toxin derivatives decreased in organisms fed artificial feed, and no B1 was detected during this treatment. Toxin composition was not significantly different between starved and kelp-fed treatments. For these abalone, neoxanthin (NEO) and B1 derivatives increased, whereas gonyautoxin (GTX)-2+3 decreased. The need for including non-traditional vectors such as abalone in routine monitoring programs is clearly evident.