Paralytic shellfish poisoning is caused by which toxin?

• A. Aflatoxin
• B. Saxitoxin
• C. Tetrodotoxin
• D. Mercury

Answer: (B)

Paralytic shellfish poisoning is caused by a potent neurotoxin called saxitoxin. This toxin is produced by certain dinoflagellates and can accumulate in shellfish through their filter-feeding. Saxitoxin works by blocking voltage-gated sodium channels on nerve and muscle cells, which stops the propagation of electrical signals. The result is numbness, tingling, dizziness, weakness, and in severe cases, respiratory failure. Among the listed substances, saxitoxin is the one specifically associated with PSP in shellfish, whereas aflatoxin is a mold-derived liver carcinogen, mercury is a heavy metal with broad neurotoxic effects, and tetrodotoxin, while also a strong sodium channel blocker, is linked to pufferfish poisoning rather than PSP from shellfish.