Animal Toxins-How animals use chemical weapons

Toxins

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Natural Toxins-How animals use chemical weapons Text by Peter Apps

Wherever there is life there are poisons.   Plants use chemicals to make themselves indigestible or toxic to animals, microbes compete for nutrients or living space by poisoning one another, and animals use poisons to repel, disable and kill.  Modern animal toxins have two functions;  attack and defense.  Predators use them to subdue their prey, and potential victims use them to repel or disable their attackers.

If animals’ physical weapons; muscular strength, claws, teeth, spines and armour, are battle axes and broadswords, then toxins are molecular stilettos, slipping through chinks in the victim’s armour to reach the very heart of its metabolic processes.

Animals have two features that render them especially vulnerable to toxins;  they move by means of muscular contractions under the control of a nervous system, and they have circulatory systems that carry nutrients and oxygen to their tissues.   Venoms and toxins from all over the animal kingdom have converged on the same devastatingly effective battle plan; rob the victim of the voluntary movement that it needs to flee or to press home an attack by using neurotoxins to block the transmission of nerve impulses and the chemical communication from nerve to nerve, and nerve to muscle, disable the circulatory system by disrupting the heart beat and curdling the blood, and hijack the circulating fluids that usually carry nutrients and oxygen to the victim’s tissues to distribute toxins throughout its body, aided by surges and slumps in heart rate and blood pressure caused by the toxins themselves.

The molecular structures of natural biological neurotoxins have been engineered with exquisite precision to interfere with the molecular machinery of nerves and muscles.  The nerve signals that control and co-ordinate behaviour are electrochemical pulses transmitted by the movement of ions through channels that cross the nerve cell membranes.  Ion channels open as the signal arrives, and a flow of sodium ions into the fiber depolarizes the membrane and sends the voltage pulse further down the fiber.    When a nerve signal arrives, calcium channels in the cell membranes around muscle fibers open, and calcium ions flood into the muscle cells to trigger contraction at the molecular level.  Potassium channels on nerves keep them ready to transmit signals by pumping ions in the opposite direction to the sodium channels..............

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