The pufferfish (Arothron hispidus) is one of the most poisonous animals on earth because of an amine called tetrodotoxin that is present primarily in its liver and ovaries.  The structure of the tetrodotoxin molecule is shown in the insert.

Source:  Wikimedia Commons, Author: Brocken Inaglory,  CC-BY-SA  http://creativecommons.org/licenses/by-sa/3.0/deed.en