Ученые раскрыли тайну змеиного взгляда: прозрачная перепонка содержит собственные сосуды

Snakes are often described as having a permanent stare, and there is a simple anatomical reason for this. They have no eyelids at all, which means there is no blinking, no closing the eyes to rest, and no lid to shut against dust or bright light. In place of eyelids, each eye is sealed beneath a single clear scale called a spectacle, fused directly onto the surface of the eye itself. This scale is not a separate add-on but part of the skin, so it sheds and regrows along with the rest of the body during every moult. Research into this structure has also turned up something less expected: the spectacle contains its own blood vessels, which can be seen clearly under close examination and which change behaviour depending on whether the snake is resting or feels under threat. Together, these findings explain both why snakes look the way they do and how that unusual eye covering is maintained throughout their lives. Why snakes evolved without eyelids According to the study published in the journal Animals, titled ‘Anatomy, Physiology, and Disorders of the Spectacle, Subspectacular Space, and Its Lacrimal Drainage System in Squamates ’, the loss of moveable eyelids is generally linked to the ancestry of snakes rather than to any single species' habits today. Researchers widely accept that snakes descended from lizards that lived a burrowing, underground existence, and that the fused, transparent spectacle developed as protection for the eyes against soil, grit, and abrasion in that environment. Later, once the ancestors of modern snakes emerged from underground life, their eyes adapted again to cope with life above the surface. This history explains why the spectacle is found in essentially every snake species regardless of where it lives today, from desert dwellers to species that spend most of their time in water or trees, since the trait is inherited rather than shaped by each species' current surroundings. pc: canva The science behind cloudy snake eyes Because the spectacle is not a separate structure sitting on top of the eye but an actual extension of the skin, it is replaced every time a snake sheds. The outer layer of the spectacle is built from alternating layers of keratin, the same protein that makes up scales, hair, and claws, and this layer is shed along with the rest of the skin in a single piece during a normal moult. In the days before shedding, the old and new layers of the spectacle briefly separate and accumulate on top of one another, which is why a snake's eyes often look cloudy or take on a bluish tinge shortly before a shed. Once the moult is complete, the spectacle regains its full clarity, and the cycle begins again with the next shedding period, meaning the eye covering is essentially rebuilt throughout the life of the animal. How blood vessels work in snake spectacles Although the spectacle looks like plain, empty glass, it is not free of blood supply. Researcher Kevin van Doorn of the University of Waterloo found a network of blood vessels running directly through the scale while studying how snakes focus their eyes, a feature that had been documented in brief mentions from the nineteenth century. As reported by the American Public Broadcasting Service, Van Doorn also observed that this blood flow is not constant. He explained that "there are cycles of flow and no flow" in the vessels of resting snakes, and that the vessels tend to constrict when a snake feels threatened, temporarily clearing the blood from the scale so that vision is not obscured at a moment when clear sight matters most. The same vascular pattern is documented in later veterinary literature, which notes that spectacle vessels remain constricted for longer during activity and dilate again during the renewal phase of shedding.