Accumulation and Elimination Profiles of Paralytic Shellfish Poison in the Short-necked Clam Tapes japonica Fed with the Toxic Dinoflagellate Gymnodinium catenatum

Abstract

The paralytic shellfish poison (PSP)-producing dinoflagellate Gymnodinium catenatum (Gc) was fed to the short-necked clam Tapes japonica, and the accumulation, transformation and elimination profiles of PSP were investigated by means of high-performance liquid chromatography with postcolumn fluorescence derivatization (HPLC-FLD). The short-necked clams ingested most of the Gc cells (4ῌ10 6 cells) supplied as a bolus at the beginning of the experiment, and accumulated a maximal amount of toxin (181 nmol/10 clams) after 12 hr. The rate of toxin accumulation at that time was 16῍, which rapidly decreased thereafter. During the rearing period, a variation in toxin composition, derived presumably from the transformation of toxin analogues in the clams, was observed, including a reversal of the ratio of C2 to C1, and the appearance of carbamate (gonyautoxin (GTX) 2, 3) and decarbamoyl (dc) derivatives (decarbamoylsaxitoxin (dcSTX) and dcGTX2, 3), which were undetectable in Gc cells. The total amount of toxin contained in clams and residue (remaining Gc cells and/or excrement in the rearing tank) gradually declined, and only about 1῍ of the supplied toxin was detected at the end of the experiment.

Identifying the Source Organisms Producing Paralytic Shellfish Toxins in a Subtropical Bay in the South China Sea

“…Previous studies always have tended to focus more on PST accumulation, distribution, and contamination status of shellfish. ,, Routine monitoring is necessary to understand the diversity of the causative toxigenic algae at the regional scale and to clarify their biogeography and distribution. The algal species producing PSTs have seldom been identified or simultaneously linked to the occurrence of PSTs in shellfish and phytoplankton.…”

Proposed Biotransformation Pathways for New Metabolites of Paralytic Shellfish Toxins Based on Field and Experimental Mussel Samples

“…Additionally, resting cysts of these dinoflagellates and some strains of freshwater cyanobacteria have also been demonstrated to synthesize these toxins. , The accumulation, transformation, and elimination of PSTs in bivalve mollusks have been evaluated in many previous studies. For example, oysters, , mussels, − scallops, , and clams − can accumulate PSTs through filter feeding on toxic dinoflagellates, such as Alexandrium tamarense, Alexandrium catenella, Alexandrium minutum, and Gymnodinium catenatum. PSTs can also be accumulated by crustaceans, such as paddle crabs (Ovalipes catharus) and lobsters (Panulirus stimpsoni), via trophic transfer. , As a result, human poisoning events occur frequently as a result of consumption of seafood contaminated by these algal toxins. , Even benthic mollusks have been contaminated by PSTs in the arctic and subarctic Chukchi and Bering seas .…”

“…Toxin accumulation and elimination in mussels are generally faster (on the order of weeks) than those in scallops, whereas removal of toxins by clams is comparatively slow as a result of strong binding of the siphon tissue with highly toxic STX. ,, PST profiles produced by microalgae are usually modified in bivalves as a result of biometabolism. Metabolic transformation pathways, including reduction, hydrolysis, and enzyme-catalyzed reactions, have been reported in previous studies. ,− Some natural reductants in shellfish, such as glutathione and cysteine, can mediate reductive reactions, including elimination of the hydroxyl group at the N-1 site and the O -sulfate group at the C-11 position. Additionally, some enzymes can catalyze the transformation of gonyautoxins-1, -2, -3, and -4 (GTX1–GTX4) and C toxins (C1/2).…”

Paralytic Shellfish Toxins (PST)-Transforming Enzymes: A Review

“…Inactivation of the toxins' transformations by heating the tissue homogenates confirmed the enzymatic nature of the reaction [41]. Decarbamoylation was also reported in the clam species Spisula solidissima [46], Paphies donacina [47] and Paphies subtriangulata [48], geoduck clam Panopea globosa [43], short-necked clam Tapes japonica [49,50] as well as in the aforementioned Pacific littleneck clam P. staminea [24,25,38]. Lower enzymatic activity was reported for sea scallop Placopecten magellanicus [26,46], quahog Mercenaria mercenaria [51], cockle Cerastoderma edule [52], peppery furrow shell Scrobicularia plana [41] and soft-shell clam Mya arenaria [24].…”