•Saxitoxin (STX) is a potent marine biotoxin
•STX and its analogs are synthesized in both marine and freshwater environments by dinoflagellates of the genus Alexandrium
•Saxitoxin enters the water column as a by-product of massive dinoflagellate proliferation and aggregation
•Saxitoxin is an inhibitory neurotoxin that induces flaccid paralysis by actively suppressing excitation of neuronal impulses