Occurrence of paralytic shellfish toxins in Cambodian Mekong pufferfish Tetraodon turgidus: Selective toxin accumulation in the skin

Abstract

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.

Toxins of Pufferfish—Distribution, Accumulation Mechanism, and Physiologic Functions

“…Each fish was intramuscularly administered 0.1 ml (50 MU) of either purified or crude TTX solution and immediately returned to the tank. Then, 5 fish from each group were randomly collected at 1,4,8,12,24,72,120, and 168 h after toxin administration and the toxin amount of each tissue was quantified by enzymelinked immunosorbent assay (ELISA) for TTX (Kawatsu et al 1997;Ngy et al 2008).…”

“…The methyl group on carbamoyl moiety appears to prevent the toxin molecules from converting into fluorescent purine derivatives (Quilliam and Janecek 1993) on post-column oxidation in HPLC-FLD analysis, although the mechanisms underlying there remain to be elucidated. (Ngy et al 2008) Wild specimens of the Mekong pufferfish Tetraodon turgidus (n = 72) and Tetraodon sp. (n = 15) were collected from several lakes in Kandal and Phnom Penh, Cambodia, respectively, from April 2005 to January 2006.…”

“…In the United States, Floridian Sphoeroides pufferfish caused 28 cases of food poisonings during 2002 to 2004, whose main toxic principle was subsequently identified not as TTX, but as paralytic shellfish poison (PSP) (Landsberg et al 2006). As described later, poisonings due to PSP-bearing freshwater pufferfish sometimes occur in Southeast Asian countries (Kungsuwan et al 1997;Ngy et al 2008;Zaman et al 1997). Since 1990, a series of poisonings due to ingesting boxfish, a family of pufferfish, have occurred in western Japan, involving 13 patients and 1 death (Taniyama et al 2009b).…”

Tetrodotoxin – Distribution and Accumulation in Aquatic Organisms, and Cases of Human Intoxication

“…The toxin of brackish water species was identified as TTX [27,28], but in the freshwater species, saxitoxins (STXs), toxins that belong to the paralytic shellfish poison (PSP) family, were detected as the main toxic principles [29,30]. Freshwater pufferfish, Colomesus asellus from Brazil [31] and T. turgidus from Cambodia [32], also possess PSP. Recently, some marine pufferfish (Arothron spp.)…”

“…Small-sized brackish water and freshwater pufferfish have also occasionally caused food poisoning incidents, including fatal cases in Asian countries such as Thai, Bangladesh, and Cambodia [32,106,107], though the causative toxin is PSP or palytoxin-like toxin in freshwater species.…”