Species Identification and Tetrodotoxin Toxicology
Domain focus
This domain tests whether you can identify permitted fugu species and explain organ-specific tetrodotoxin (TTX) risk. The exam expects species-level caution, not a blanket “fugu is poisonous” answer.
Core rules
- TTX is a heat-stable, water-soluble marine toxin. Ordinary cooking, freezing, salting, or rinsing does not make a toxic organ safe.
- Identify species using several features together: body shape, skin pattern and spination, fin-ray counts, head and mouth form, and origin. A single color mark is not enough.
- TTX distribution differs by species, season, and individual. Liver and ovary are usually the highest-risk organs; intestine, skin, and eyes can also be toxic. Muscle is often low-risk in commonly handled species, but this must be confirmed against the prefectural permitted-species and edible-part list.
- The local list, not memory or rumor, decides which species and parts may be sold. If the species is not clearly permitted, do not process it.
Worked example
A trainee sees a striped back, calls the fish torafugu, and says the fillet is safe because the liver was removed. The correct reasoning is: confirm identity with fin rays, skin, and head shape; confirm torafugu is permitted locally; confirm the edible-part rule for muscle; then check that liver removal did not contaminate the fillet through knife, board, or hands. Removal alone does not prove safety.
Traps
Assuming all fugu muscle is safe; treating cooking as detoxification; identifying from one photo; ignoring species-specific organ rules; and using a prefectural rule from another region.