| Résumé | Bivalve molluscs can acquire diarrhetic shellfish poisoning (DSP) toxins via ingestion of toxigenic dinoflagellates. The dynamics and fate of DSP toxins were investigated in the bay scallop Argopecten irradians exposed to cells of the epibenthic dinoflagellate Prorocentrum lima, a known producer of DSP toxins, in controlled laboratory microcosms. Toxin parameters determined were uptake and detoxification rates, and anatomical compartmentalization. Toxins in tissue and algal extracts were analyzed by liquid chromatography-mass spectrometry (LC-MS). No mortalities occurred and feeding inhibition was not observed for juvenile and adult bay scallops during the 2 wk exposure to P, lima cells. Clearance rates were similar for scallops exposed to equivalent biovolume cell concentrations of toxigenic P. lima and the non-toxic diatom Thalassiosira weissflogii; however, absorption efficiency of organic matter was significantly lower with a diet of P. Lima than T. weissflogii, Although DSP toxin concentrations in viscera of bay scallop exceeded commonly accepted regulatory levels (0.2 mug g(-1) whole tissue) within 24 h of exposure to P. lima, after 2 wk of exposure total DSP toxin retained in scallop tissues was <1 % of the total toxin ingested over the same period. Most of the total toxin body burden was in the viscera (76 %); however, in adult scallops a significant portion was associated with gonadal tissue (12 %). Toxin levels were relatively low in gill, mantle and adductor tissue (< 12% of total toxin body burden). During the depuration period, rapid release of DSP toxins from scallops indicated that toxins were poorly bound to all tissues, with the exception of the viscera. Detoxification of viscera consisted of a rapid loss of weakly bound toxin components within the initial 3 d of depuration, followed by a much slower release of the remaining toxin at a rate of 8.4 % d(-1). |
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