Transfer of Paralytic Shellfish Toxins via Marine Food Chains:A Simulated Experiment

Objective To study the transfer of paralytic shellfish toxins （PST） using four simulated marine food chains： dinoflagellate Alexandrium tamarense→Artemia Artemia salina→Mysid shrimp Neomysis awatschensis; A. tamarense→N. awatschensis; A. tamarense→A, salina→Perch Lateolabrax japonicus; and A. tamarense→L, japonicus. Methods The ingestion of A. tamarense, a producer of PST, by L. japonicus, N. awatschensis, and A. salina was first confirmed by microscopic observation of A. tamarense cells in the intestine samples of the three different organisms, and by the analysis of Chl.a levels in the samples. Toxin accumulation in L. japonicus and N. awatschensis directly from the feeding on A. tamarense or indirectly through the vector of A. salina was then studied, The toxicity of samples was measured using the AOAC mouse bioassay method, and the toxin content and profile of A. tamarense were analyzed by the HPLC method. Results Both A. salina and N. awatschensis could ingest A. tamarense cells. However, the ingestion capability of A. salina exceeded that of N. awatschensis. After the exposure to the culture of A. tamarense （2 000 cells·mL^-1） for 70 minutes, the content of Chl.a in A. salina and N. awatschensis reached 0.87 and 0.024 μg.mg^-1, respectively. Besides, A. tamarense cells existed in the intestines of L. japonicus, N. awatschensis and A. salina by microscopic observation. Therefore, the three organisms could ingest A. tamarense cells directly. A. salina could accumulate high content of PST, and the toxicity of A. salina in samples collected on days 1, 4, and 5 of the experiment was 2.18, 2.6, and 2.1 MU.g^-1, respectively. All extracts from the samples could lead to death of tested mice within 7 minutes, and the toxin content in anemia sample collected on the 1st day was estimated to be 1.65×10 ^5 μg STX equal/individual. Toxin accumulation in L japonicus and N. awatschensis directly from the feeding on A. tamarense or indirectly from the vector ofA. salina was also studied. The mice injected with extracts from L japonicus and N. awatschensis samples that accumulated PST either directly or indirectly showed PST intoxication symptoms, indicating that low levels of PST existed in these samples. Conclusion Paralytic shellfish toxins can be transferred to L. japonicus, N. awatschensis, and A. salina from A. tamarense directly or indirectly via the food chains.

Comparative study on in vitro transformation of paralytic shellfish poisoning (PSP) toxins in different shellfish tissues

Dissected tissues of three shellfish species, the Chinese scallop, Chlamys farreri, Manila clam, Ruditapes philippinarurn, and Razor shell, Solen strictu were evaluated for in vitro transformation of paralytic shellfish poisoning （PSP） toxins. Tissue homogenates were incubated with extraction from toxic algae Alexandriurn rninutura to determine toxin conversion. The effects of heating and addition of a natural reductant （glutathione） on toxin conversion were also assessed. The toxin profile was investigated through high performance liquid chromatography with fluorescence detection （HPLC-FLD）. The evident variations in the toxin content were observed only in Chinese scallop viscera homogenates. The concentration of GTX4 was reduced by 45% （approximately 0.8 μmol/dm^3） and 25% （approximately 1 μmol/dm^3） for GTX1, while GTX2 and GTX3 increased by six times （approximately 1 μmol/dm^3） and 3 times （approximately 0.3μmol/dm^3） respectively. Simultaneously, the total toxicity decreased by 38% during the 48 h incubation period, the final toxicity was 20.4 nmol STXeq/g. Furthermore, heated Chinese scallop viscera homogenates samples were compared with non-heated samples. The concentration of the GTX4 and GTX1 was clearly 28% （approximately 0.53 μmol/dm^3） and 17% （approximately 0.69μmol/dm^3） higher in heated samples, GTX2 and GTX3 were four times （0.66 μmol/dm^3） and two times （0.187 μmol/dm^3） lower respectively. GSH （＋） Chinese scallop viscera homogenates samples were compared with GSH （-） samples, the concentration in the GTX4 and GTX1 was 9% （approximately 0.12 μmol/dm^3） and 11% （approximately 0.36 μmol/dm^3） lower respectively, GTX2 and GTX3 was 17% （approximately 0.14 μmol/dm^3） and 19% （approximately 0.006 μmol/dm^3） higher respectively. In contrast,there was a little change in the concentration of PSP toxins of Manila clam and Razor shell tissue ho- mogenates. These observations on three shellfish tissues confirmed that there were species-specific differences in PSP toxins transformation. PSP toxins transformation was more pronounced in viscera tissue than in muscle tissue. PSP toxins was possibly interfered by some carbamoylase enzyme, and the activity in Chinese scallop viscera tissue is more remarkable than in the other two species.