Why can some species of cobras spray venom precisely into the victim's eyes?
If cobra venom gets into the eyes, it will cause severe pain and even lead to permanent blindness .
Some spitting cobras can shoot venom from their fangs into the victim's eyes from more than 1.5m away even while they are moving with about 90% accuracy.
They are capable of predicting target locations in as little as half the blink of an eye.
Ability to spray venom accurately even while moving
Some species of cobra can spray venom accurately into the victim's eyes from a distance of 1.5m. (Photo: Shutterstock).
To analyze the deadly venom-spitting ability of cobras , functional morphologist Bruce Young, University of Massachusetts (USA), stood behind a sheet of plexiglass and recorded the venom-spitting process of South African cobras as they targeted his eyes.
The expert found that snakes tend to wiggle their heads before spitting venom.
Not only Young, herpetologist Guido Westhoff, University of Bonn (Germany), also recorded this phenomenon in cobras.
During their work together, Young was responsible for stimulating the snakes to spit venom, while Westhoff was responsible for recording the snakes' head movements. Other researchers were responsible for filming the cobras' movements.
They found that the animal makes up to 500 movements per second, about 20 times faster than the speed of an average camera.
Over six weeks, researchers recorded 100 venom spits from the snakes. When analyzed, they found that the snakes could detect the movements of their opponents 0.2 seconds in advance, half the time it takes to blink an eye.
In that split second, the snake can orient its venom spray so that it can aim precisely at the victim's eyes.
"If just a small drop of pure or diluted snake venom gets into the eye, the cornea will immediately become paralyzed, and the victim will be unable to see anything afterwards ," Young told Live Science.
Additionally, according to Young, the ability of some species of cobras to accurately spray venom while moving is a feature that is not very common in snakes or reptiles in general.
After being bitten by snake venom, the victim's eyes (left) will gradually become blurred and lose the ability to see. (Photo: Healio).
The speciality of the venom that is sprayed
Scientists at the Liverpool School of Tropical Medicine (UK) analyzed the venom of 17 species of spitting and non-spitting snakes to find the differences between them.
Accordingly, the most common compound in cobra venom is called "3-finger" toxin . This substance accounts for 60% of snake venom in general.
However, the venom of the spitting cobra contains a lot of the toxin phospholipase A2 . This toxin is very little or almost non-existent in the venom of non-spitting snakes.
Through experiments on mice, researchers discovered that the "3-finger" toxin when combined with phospholipase A2 has the ability to cause more severe pain .
Specifically, the venom of the spitting snake has the ability to stimulate mouse nerve cells twice as much as the venom of the non-spraying snake.
Sharing on Science, biologist Nicholas Casewell, the venom of some snakes has evolved to help them have better defense capabilities.
Sharing the same opinion, toxicologist Stephen Mackessy, University of Northern Colorado (USA), snakes evolved venom that makes them blind as a way for these animals to scare away other predators.
However, the reason why snakes evolved to spit venom remains unclear.
Some researchers believe this is how snakes protect themselves from being trampled by large mammals, whose eyes are difficult to attack with venom rays.
According to Casewell, prehistoric humans are the reason snakes evolved to spit venom.
"Our ancestors were a threat to snakes. Humans have forward-facing eyes, which are not shielded or protected. This could be a good target for snakes to evolve to spray venom at humans ," he analyzed.
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