**Question:** Which of the following toxin is responsible for manifestations of puffer fish poisoning?

**Core Concept:** Puffer fish poisoning is caused by the ingestion of fang toxin, which is a potent neurotoxin.

**Why the Correct Answer is Right:** The correct answer, tetrodotoxin (TTX), is a potent neurotoxin produced by the puffer fish and other marine organisms. TTX blocks voltage-gated sodium channels in the nervous system, leading to the characteristic clinical manifestations of puffer fish poisoning.

**Why Each Wrong Option is Incorrect:**

A. TTX is not responsible for puffer fish poisoning, as mentioned above, it is the fang toxin that causes the poisoning.
B. This option refers to a different toxin (tetrodotoxin-like) that is not the primary toxin responsible for puffer fish poisoning.
C. This option refers to another toxin (paralytic shellfish poisoning toxin) that is not responsible for puffer fish poisoning.
D. This option refers to another toxin (scopolamine) that is not related to puffer fish poisoning but rather a parasympathetic antagonist.

**Clinical Pearl / High-Yield Fact:** Puffer fish poisoning is a clinical emergency that requires immediate medical attention. Symptoms include flaccid paralysis, respiratory failure, and cardiac arrhythmias. Antidotes are currently not available, so supportive care is crucial in managing the poisoning.

**Correct Answer:** D. Scopolamine