I have never seen a marine animal bothering a ray. These gentle creatures evolved from the generational branch of sharks and, although they modified their body to adapt to the sandy bottom, they retain some characteristics of their “cousins,” the sharks, including their skin.
In the skin of rays, some layers of cells undergo ossification, so it could be said that their scales are formed by bones. These scales have a bony plate that serves as a base for a small, sharp, and strong enamel spine called a dermal denticle, which points towards the tail. These denticles, when seen under a microscope, are very similar in structure to our own teeth.
The placoid scales appear in tightly packed rows, leaving very little space between their edges. The denticles protrude from the mucous layer of the skin and are what give the rough texture to the skin of rays. This bony structure formed on the skin creates a flexible and almost impenetrable armor. Even a strong man armed with a sharp knife would find it extremely difficult to stab a ray, so there is no hope for the teeth of predators.
It might seem curious that rays have rough skin since it should increase the friction of the animal with the water. However, the regular arrangement of the denticles channels the water, producing a laminar flow that significantly reduces friction. This laminar flow could even make rays, as well as sharks, “hydrodynamically silent,” giving them a great advantage in surprising their prey or going unnoticed.
Protected by this flexible armor, rays leisurely swim over the reef and take long naps on the sandy bottom, barely covered by sand. When divers approach, they show themselves as docile animals and allow them to stroke their curious skin before taking flight like a bird. They slowly move away, enveloped in teeth and mystery.
“You cannot defend what you do not love, and you cannot love what you do not know.”