Crocodile tears look a lot like human ones

The expression 'crocodile tears' It is applied to those types of false tears that denote hypocritical sadness and that have their origin in the belief that crocodiles cried while devouring their prey.

However, a recent study reveals that crocodile tears are strikingly human-like in terms of chemical composition– something that, since crocodiles have not changed much for millions of years, could provide insight into how the human eye has evolved and facilitate new treatments for eye diseases.

Most of the previous studies that have analyzed the chemical composition of tears in animals have focused on other mammals, such as dogs, horses or monkeys. However, researchers from Saudi Arabia and Brazil have analyzed, for the first time, the tears of different reptiles and birds.

First study in birds and reptiles

In their study, published in the scientific journal 'Frontiers in Veterinary Science', the scientists detail the analysis of the tears of seven species (owls, blue and yellow macaws, road snails, broad-snouted alligators and loggerhead, hawksbill and green sea turtles) and their tear ducts and other similar glands.

"Discovering how tears are able to maintain ocular homeostasis is essential for the discovery of new molecules for ophthalmic drugs"

"There was more total protein and urea in owl and sea turtle tears, respectively, than in the other animals tested. The electrolyte balance was similar for all species, with more sodium, chloride and iron, "write the study authors.

This does not mean that the tears of animals and humans are the same. Human tears had higher levels of protein compared to other species, offering greater stability of the ocular surface. Alligators and owls offered even higher concentrations of protein, probably because both species have very large eyes and rarely blink.

The people blink every 10-12 seconds while alligators can keep their eyes open without blinking for up to two hours.

"Discovering how tears are able to maintain ocular homeostasis, even in different species and environmental conditions, is crucial to understanding the evolution and adaptation processes, and it is essential for the discovery of new molecules for ophthalmic drugs ", explains Arianne P. Oriá, from the Federal University of Bahia (Brazil), to ZME Science.

Eye health treatments

Tears play an important role in keeping your eyes healthy. Mainly, are made up of mucus, oil, and water, which bind to coat the eye preventing it from drying out and supplying crucial proteins and minerals. Tears also prevent infection and lubricate the eye, cleaning debris. In humans, tears are also an expression of our emotional states.

Even if no other animal is known to cry, the new study shows that at least chemically speaking, human tears are not as different from those of reptiles as alligators.

Tears also prevent infection and lubricate the eye, cleaning debris. In humans, tears are also an expression of our emotional states

As noted in the study, the surrounding environment has a major impact on the composition of tears. Because tears are the body fluids most exposed to the outside world, their composition will easily change when the environment is altered, such as due to pollution. This can have a detrimental effect on eye health.

In the future, the researchers plan to analyze the tears of more species, as well as expand their knowledge about them with the aim of developing new treatments for eye problems, both in humans and animals.