To reveal the accumulation profile of tetrodotoxin (TTX) in pufferfish Takifugu rubripes juveniles, we compared the localization of TTX in various tissues among wild juveniles and hatchery-reared juveniles with or without TTX administration using immunohistochemical technique with anti-TTX monoclonal antibody. Immuno-positive reaction was observed in hepatic tissue, basal cell of skin and olfactory, olfactory epithelium, optic nerve and brain (optic tectum, cerebellum, medulla oblongata) of wild juveniles (body length: BL, 4.7-9.4 cm). TTX was detected in the same tissues as wild juveniles and epithelial cell layer of intestine of hatchery-reared juveniles (BL, 5.0-5.3 cm) to which TTX was orally administrated. No positive reaction was observed from the tissues of hatchery-reared juveniles without TTX administration. These results suggest that orally administrated TTX to the non-toxic cultured juveniles is accumulated in the same manner of wild juveniles. In addition, our study revealed that pufferfish accumulates TTX in the central nervous system.

We examined the effects of tetrodotoxin (TTX) administration to the artificially-raised tiger puffer Takifugu rubripes juveniles on the survival after release into a mesocosm with predators in order to clarify the ecological significance of TTX. Artificial pellets containing 3 different concentrations of TTX (0 as control, 7, 14 MU/g•diet) were fed to non-toxic artificially-raised T. rubripes juveniles for 10 days. TTX accumulation in the various tissues of fish was detected except for control diet group, and TTX administration did not affect survival or growth of the fish. Then, a hundred fish from each diet group were released together into a salt-pond mesocosm (2,650 m 2) with predators (Lateolabrax sp.) for 5 days. Survival after release was significantly higher in the fish fed with TTX both 7 MU/g•diet (62 %) and 14 MU/g•diet (74 %) than the control fish (32 %).