Change in tetrodotoxin content of the puffer fish Takifugu rubripes during seed production from fertilized eggs to juveniles.

Changes in tetrodotoxin (TTX) content of the puffer fish Takifugu rubripes during seed production were examined. Two mature female puffer fish T. rubripes (samples 1 and 2) that contained TTX were used. The toxic eggs were artificially fertilized, and hatchlings were reared in an indoor tank for 50 days and then in a netcage at sea for an additional 48 or 38 days. The TTX content of the fertilized eggs of sample 1 was initially 13.0 microg TTX/g, transiently increased to 67.6 microg TTX/g at 4 days after hatching, and then gradually decreased to 0.28 microg TTX/g at 98 days. In contrast, the total TTX content in an individual was 0.016 microg TTX at the fertilization stage and 0.01-0.03 microg TTX at the larval stage until 30 days after hatching. Thereafter, the total TTX content increased remarkably during culture in the netcage at sea, reaching 4.80 microg TTX at 98 days. Change in the TTX content of sample 2 showed a similar tendency to that of sample 1. The present study showed that the TTX content per gram of puffer fish body weight decreased during progression from fertilized eggs to juveniles, whereas the total TTX content increased.