Natural killers: God’s lethal creations
- Deeksha Raghuram
- Aug 27, 2025
- 5 min read
-Banded Sea Krait - highly venomous
Introduction :
Something that has always fascinated me is the varied arsenal of weapons that mother nature’s children use to hunt unfortunate prey or defend themselves from danger. Some animals use sharp teeth and claws to tear their victims apart, but other creatures have their own kit of poisons at their disposal.
The sheer variety of natural poisons and the methods by which they kill, have been a source of curiosity for scientists across generations, and a source of great anxiety for healthcare workers whose patients have been affected by these toxins.
There’s something terrifyingly beautiful in the way evolution has led almost all of nature to follow one rule without fail, which is, the more colorful you are, the more likely you are to poison me.
This is true for the stunning banded sea krait we see near the Australian coast, for the dangerous poison arrow dart frogs in South American forests, which come in bright shades of blue, red and yellow, and even for the elegant monarch butterfly, which uses its orange and black colors to warn predators of its poisonous nature.
Plants are no exception to this evolutionary marvel. Some of the most potent poisons and chemicals we see everyday, even in the medical field come from plants.
Atropine, formerly used in emergency medicine to treat cardiac arrest, and hemlock, a poison famously used in Ancient Greece to execute Socrates, both come from plants. Opium, coming from the humble poppy plant, has ignited war between Britain and China, while also finding a use as a painkiller, and cocaine, derived from Erythroxylum Coca, has thrown entire nations into disarray.
Let’s dive deeper into these toxins, and why and how they affect us the way they do.
Gallery:
Plant poisons:
Strychnine :
A poison produced by the poison nut tree, native to Southern India and Sri Lanka, originally intended to deter herbivores from grazing on the plant, it found its place in Victorian era England, where it was used as a stimulant, mainly to enhance athletic performance. It also made an appearance in Agatha Christie’s famous novel : The Mysterious Affair At Styles, where the victim is poisoned to death by strychnine.
Many morbidly referred to this as the poison that kills you while you have a smile on your face, mainly due to the involuntary and often painful muscle spasms it causes. In medical terms, this is known as “Risus Sardonicus.”
● Competitive Inhibition : It competes with glycine to bind to inhibitory post-synaptic receptors in your spinal cord. Simply put, it prevents you from having control over when your neurons fire, causing involuntary movements and spasms.
● Uncontrolled muscle spasms cause various ill effects, including tachycardia, which is a spike in heart rate, and respiratory spasms, which cause airway closure and suffocation.
● Not only that, but unchecked and repetitive muscle contraction causes lactic acid to accumulate in your muscles, causing lactic acidosis, and increases body temperature, both of which interfere in bodily mechanisms.
Strychnine poisoning has no specific antidote, victims of this poison are often made to ingest activated charcoal to absorb the poison from their body, and artificial ventilation is given. The convulsions are managed using benzodiazepine, a CNS depressant.
Atropine :
A poison derived from the plant, Atropa Belladonna, it has gone by many names throughout history, and had many uses. The plant it comes from gains its name, Belladonna, which means beautiful woman in Italian, due to women in 16th Century Italy using this plant to dilate their pupils, which was considered a sign of beauty back then. Deadly nightshade has been called the “Drug of Assassins", because atropine was the drug used for many assassination attempts in the past.
Atropine, as I mentioned before, was also used in emergency medicine to treat cardiac arrest, and even used to treat victims of nerve gases such as Sarin.
Let’s find out why and how it affects our body so potently.
● Atropine is an anticholinergic alkaloid, it competitively and reversibly binds to Acetylcholine (Ach) receptors in the body, inhibiting Vagal response and parasympathetic action.
● This means that Atropine competes with Ach, a neurotransmitter in our body, to bind to its receptor. Once atropine binds, Ach cannot bind to its own receptor, and hence cannot carry out its functions, which include mediating muscle contraction and maintaining heart rate.
● Nerve gases and organophosphorus compounds cause buildup of Ach which in this case is permanent, leading to overstimulation of nerve cells, involuntary responses and death. Atropine combats this by reducing the effect of the accumulated Ach, through its competitive inhibition, making it a useful antidote.
● The vagus nerve uses Ach to mediate parasympathetic response, which slows your heart rate, and if that cannot be carried out, sympathetic stimulation dominates. This is the principle behind using Atropine to treat cardiac arrest.
● The end result of a high dose of atropine is Tachycardia, increased heart rate, thanks to sympathetic predomination. This can kill you if left unchecked, because Tachycardia causes decreased blood flow to the heart, which damages heart tissue and leads to heart failure.
● Along with tachycardia, delirium, pupil dilation, and dry, warm skin, are the symptoms of atropine poisoning. Atropine poisoning is treated using Physostigmine, which temporarily causes Ach accumulation, leading to more binding of Ach to its own receptor.
Animal venom:
King Cobra:
The king cobra earns its spot as the king of snakes, with its highly potent venom, consisting of a cocktail of deadly toxins, and its cannibalistic tendency to prey on fellow snakes. Its diet consists of cobras, pythons, rat snakes, kraits, vipers, and even other king cobras, and sometimes it preys on small reptiles and rats when food is scarce.
Despite its cobra-like hood and its name, king cobras are not true cobras, in fact, they are more closely related to mambas. These beautiful creatures are found mainly in Asia, their habitat ranging from the Western Ghats in India, to highlands in Thailand and Malaysia.
King cobra bites are deadly for two reasons, one reason being the effects of their venom, and the second, is the sheer amount of venom they inject per bite. They inject upto 1000mg of venom per bite. To put that into perspective, regular cobras inject 250mg of venom per bite. So despite having relatively less deadly venom than other snakes, it makes up for it with the quantity it delivers, with one bite being enough to incapacitate an elephant.
The effects of the venom itself are mainly due to compounds known as 3 finger toxins, which destroy cells and interfere with neurotransmitter binding, acting as neurotoxins and cytotoxins. Some of them can also interfere in blood clotting, acting as anti-coagulants. The venom also contains phospholipase A2, which breaks down fatty acids.
One constituent of the venom, L-Amino Acid Oxidases (LAOO) is being studied for its anti tumor and anti cancer properties. This compound has been effective against leukaemia cells and against breast cancer cells as well. It reduces their ability to multiply, and induces death in these cells.
This may be a scary and slightly morbid topic to discuss. Poison is meant to kill and harm living beings. But no matter what we do, toxins will always exist in one way or another. It is upto us to find antidotes and treatments for those affected, and maybe, even turn something so deadly and potentially fatal, into something that can be used to make lives better.
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