Most people and animals cry tears, while some have other ways to express sorrow or fear. This line contradicts the existence of horned lizards!
What may seem like a made-up statement is a very interesting trait of these types of lizards. North American desert horned lizards are quite special, since they have members living in the same habitat shoot blood out of their eyes! This sounds like a superpower, but it has a scientific explanation to it. What is used as a defence mechanism involves their ocular sinuses, tissues which are present below their eyes.
The Biology
The horned lizard has veins around its eyes connected by two constricting muscles. The contraction of these muscles is what cuts the flow of blood back to the heart. The ocular sinuses are then filled with blood, and the pressure causes them to bulge. As the contraction happens often in a rapid manner, the thin sinus membranes are ruptured.
The result
The rupturing allows these horned lizards to shoot blood upto 4-feet from the eye socket! This is also known as auto-hemorrhaging. The lizard uses this to clean its eye at times, when it feels some particles on the surface. The most common usage is protection from predators. After the process, a thin third eyelid is swept across the surface of the eye. It is transparent in nature, and folds back to the front corner of the eye. The debris is drawn away from the rear of the eye and onto the eyelid.
Following is the blood squirting activity performed, making the skin around the eyelids expand and the debris falls off.
The horned lizards differ in colours and sizes, and each lizard has a different number of horns and arrangements of horns on their backs. They are not built for speed, as they have short legs and long bodies. The blood squirting tactic is just one of many other tactics!
Be on alert when you see horned lizards. The blood cannot harm you, but it sure feels nasty to have some stick on your skin!
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