Toxicity of pufferfish Takifugu rubripes cultured in netcages at sea or aquaria on land☆

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Abstract

Marine pufferfish (family Tetraodontidae) are believed to accumulate tetrodotoxin (TTX) mainly in liver and ovary through the food chain by ingesting TTX-bearing organisms such as starfish, gastropods, crustacean, flatworms, ribbonworms, etc. Consequently, it is hypothesized that non-toxic pufferfish can be produced if they are cultured with TTX-free diets in netcages at sea or aquaria on land, where the invasion of TTX-bearing organisms is completely shut off. To confirm this hypothesis, more than 5000 specimens of the pufferfish (“torafugu”, Takifugu rubripes) cultured in such manners for 1–3 years were collected from several locations in Japan during 2001–2004, and toxicity of their livers and some other parts was examined according to the Japanese official mouse assay method for TTX. In addition, typical specimens were submitted to LC/MS analysis. The results showed that all the livers and other parts tested were ‘non-toxic’ in both of the mouse assay (less than 2 MU/g) and LC/MS analysis (less than 0.1 MU/g). Thus, it is undoubtedly confirmed that pufferfish are intoxicated through the food chain, and non-toxic pufferfish can be successfully produced by netcage or land culture. The livers from these fish can be used with safety as a Japanese traditional food “fugu-kimo” (puffer liver).

Introduction

Many years of studies on puffer toxin, tetrodotoxin (TTX), have demonstrated that (1) toxicity of pufferfish shows remarkable individual and regional variations (Miyazawa and Noguchi, 2001), (2) pufferfish become non-toxic when they are artificially reared with non-toxic diets after hatching (Matsui et al., 1982, Saito et al., 1984), (3) non-toxic pufferfish like (2) become toxic when administered orally with TTX (Matsui et al., 1981, Yamamori et al., 2004, Honda et al., 2005a), (4) TTX is distributed over many organisms including food animals of pufferfish such as starfish, gastropods, crustacean, flatworms, ribbonworms, etc. (Miyazawa and Noguchi, 2001), and (5) marine bacteria originally produce TTX (Noguchi et al., 1986, Hashimoto et al., 1990). These facts strongly suggest that pufferfish do not synthesize TTX by themselves, but accumulate it through the food chain that starts from marine bacteria.

Recently, Nagashima et al. (2003) reported that liver tissue slices of pufferfish accumulated considerable amount of TTX in vitro, when incubated with a medium containing TTX. This phenomenon was not observed in general non-toxic fishes, suggesting the presence of specific mechanism whereby the puffer liver actively accumulates TTX. In this connection, it is also known that TTX binding proteins exist in the blood plasma of pufferfish, which may possibly be implicated in the transportation of TTX in puffer body (Matsui et al., 2000, Yotsu-Yamashita et al., 2001). However, detailed mechanisms of uptake, accumulation, metabolism and excretion of TTX in pufferfish remain to be elucidated.

Regarding the biological significance of TTX in TTX-bearing animals, the function as a defensive agent has been pointed out, based on the facts that eggs usually contain much amounts of TTX (Miyazawa and Noguchi, 2001), and that pufferfish and newts have TTX-secreting glands or cells in their skin (Tanu et al., 2002, Tsuruda et al., 2002, Mahmud et al., 2003a, Mahmud et al., 2003b) and release a considerable amount TTX by external stimuli (Kodama et al., 1985, Saito et al., 1985, Tsuruda et al., 2002). In this connection, we found very recently that immunity of cultured pufferfish was significantly activated when they reared with TTX-containing diets, although the mechanism is unclear (Honda et al., 2005b).

During the course of these studies to elucidate the accumulation mechanism and biological function of TTX in pufferfish, we were interested in the toxicity of cultured pufferfish. If the TTX of pufferfish actually comes from the food chain as mentioned above, non-toxic pufferfish can be produced when they are cultured with TTX-free diets in netcages at sea or aquaria on land where the invasion of TTX-bearing organisms is completely shut off. To confirm this hypothesis, the present study was conducted.

Section snippets

Materials

From 2001 to 2003, a total of 4133 specimens of the pufferfish Takifugu rubripes (juveniles to 3 years old fish) cultured in netcages (usually 10 m long × 10 m wide × 4 m deep; more than 10 m apart from the sea bottom) were collected from Nagasaki, Kumamoto, Ehime, Kagoshima, Wakayama and Shizuoka Prefectures (Fig. 1). Liver of all the specimens, and muscle, skin, gonads and other viscera of 26 specimens out of them were submitted to the toxicity assay using mice. In addition, livers of 20 typical

Results and discussion

Toxicity of the livers of cultured pufferfish is shown in Table 1. All specimens assayed (4133 specimens from netcage culture and 910 specimens from land culture) showed no toxicity against mice (less than 2 MU/g). Muscle, skin, gonads and other viscera of 26 specimens from netcage culture, and ovary of 14 specimens from land culture also exhibited no toxicity at all (Table 2). The collection places of these specimens cover most of the main puffer-culturing areas in Japan, and sample

Acknowledgements

The authors express their sincere gratitude to Mr. Kiyofumi Kikuno, Mr. Masamitsu Terada and Mr. Manabu Naito, Graduate school of Science and Technology, Nagasaki University, and Ms. Yoshimi Himemiya, Faculty of Fisheries, Nagasaki University for their excellent assistance in toxicity assay. The authors also acknowledge to Kanmonkai Co., Takashima-Aou Fisheries Cooperative, Ogawa Fisheries Co., Kinashi-Fugu Kyushu Store Co., Manbou Co., Inc., and Numazu Culture Fisheries Cooperative for their

References (23)

  • M. Kodama et al.

    External secretion of tetrodotoxin from puffer fishes stimulated by electric shock

    Mar. Biol.

    (1985)

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    ☆

    This paper was presented at the TODAI International Symposium on Functional Genomics of Pufferfish Recent Advances and Perspective, The University of Tokyo, Yayoi Auditorium, Tokyo, Japan, 3rd–6th Nov 2004.

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