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The toxicity of two species of wild Cambodian freshwater pufferfish of the genus Tetraodon, T. turgidus and Tetraodon sp., was investigated. Tetraodon sp. was non-toxic.The toxicity of T. turgidus localized mainly in the skin and ovary. Paralytic shellfish toxins (PSTs), comprising saxitoxin (STX) and decarbamoylsaxitoxin (dcSTX) account for 85% of the total toxicity. Artificially-reared specimens of the same species were non-toxic. When PST (dcSTX, 50 MU/individual) was administered intramuscularly into cultured specimens, toxins transferred via the blood from the muscle into other body tissues, especially the skin. The majority (92.8%) of the toxin remaining in the body accumulated in the skin within 48 h. When the same dosage of TTX was similarly administered, all specimens died within 3 to 4 h, suggesting that this species is not resistant to TTX. Toxin analysis in the dead specimens revealed that more than half of the administered TTX remained in the muscle and a small amount was transferred into the skin. The presence of both toxic and non-toxic wild specimens in the same species indicates that PSTs of T. turgidus are derived from an exogenous origin, and are selectively transferred via the blood into the skin, where the toxins accumulate.

In Cambodia, fatal food poisonings associated with the consumption of pu#erfish have occurred for decades, but the causative species or toxins have never been documented. Herein, we investigated the toxicity of three pu#erfish species of the genus Lagocephalus collected from the coastal waters of Sihanouk Ville, one of the main regions where poisonings have occurred. L. wheeleri and L. spadiceus were non-toxic, whereas L. lunaris was toxic and all of its body tissues exhibited toxicity levels exceeding the safety limit for human consumption (10 mouse units/g). Tetrodotoxin (TTX) was identified as the main toxin in this species; no paralytic shellfish poison(s) were detected. Consequently, we can confirm pu#erfish to be a hazardous reservoir of TTX in Sihanouk Ville. It is likely that L. lunaris is one of the causative species of past pu#erfish poisonings that have occurred in Cambodia.

A rapid and simple detection method for tetrodotoxin (TTX) in urine and plasma of patients with puffer fish poisoning was developed using commercially pre-packed solid-phase extraction (SPE) cartridges (C18 and weak cation exchange columns) and subsequent analyses by HPLC with UV detection. The detection limit of the standard TTX, TTX-spiked urine and plasma samples were all 10 ng/ml and the average TTX recovery in urine and plasma samples after SPE were 90.3 +/- 4.0 and 87.1 +/- 2.9%, respectively. It was noticed that the creatinine-adjusted urinary TTX levels obtained within the first 24 h of presentation apparently correlated much better with the severity of poisoning than the urinary TTX concentration without adjusting for variations in concomitant creatinine excretion.

A rapid and highly specific fluorescence polarization immunoassay (FPIA) was developed for the detection of a widely used herbicide in rice cultivation, butachlor, in various polluted water samples. Three fluorescent tracers with different spacer arms and structures were synthesized to enhance the FPIA sensitivity. The effects of different fluorescent tracer structure and organic solvent concentration on the performance of the FPIA were investigated. The results showed that the fluorescent tracer 3-( 2) demonstrated the best FPIA sensitivity at pH 8.0, which remained at up to 20% methanol in a tolerance study. The IC 50 (50% inhibition concentration) of the FPIA was 207.0 ng mL À1 with the detection of butachlor ranging from 32.0 to 1218.0 ng mL À1 (at 20%-80% inhibition concentration), and the limit of detection (at 10% inhibition concentration) was 11.0 ng mL À1 . Recoveries, measured in spiked water samples, ranged from 75.1% to 134.5%. This newly developed FPIA was characterized by high specificity and reproducibility, allowing a rapid, low-cost, and sensitive determination of butachlor in polluted waters.

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