Determining the lifespan of sharks ( Selachimorpha ) is a difficult task, as they are very complicated to monitor in the ocean due to their migratory patterns and, of course, their diet. In addition, if these large predators are in captivity, they have a lower life expectancy than those found in the wild, which makes it impractical to generate deductions from the sharks that we find in aquariums.

The truth is that the lifespan of sharks varies by species. Although most of them live for 20 to 30 years in the wild , there are some that live much longer than others, such as the case of the Greenland shark that would have reached adulthood at the time of the American Revolution and would have hunted, swam and slept through four centuries of history. But this is the exception that proves the rule. And besides this, we know almost nothing about its biology or its development. As these animals do not even suffer from tissue calcification and live in very inhospitable habitats, they are great unknown to humans.

Important Considerations About Sharks

How to find out your age: counting the rings of your vertebrae

Yes, as if it were a tree, the vertebrae of sharks contain concentric pairs of opaque and translucent bands . The pairs of bands are counted as rings in a tree, and then scientists assign an age to the shark based on the count. Therefore, if the vertebra has 10 pairs of bands, it is assumed to be 10 years old. Recent studies, however, have shown that this assumption is not always correct. Therefore, researchers must study each species and size class to determine how often the band pairs are deposited because the deposition rate can change over time. Determining the actual rate at which the bands are deposited is called “validation.”

Sharks have no bones

Sharks use their gills to filter oxygen from the water. They represent a special type of fish known as “elasmobranch”, which translates to fish made of cathylaginous tissues. This category also includes stingrays or sawfish. Their cartilaginous skeletons are much lighter than the bones we know of, and their large livers are filled with low-density oils, something that helps them float.
Although sharks don’t have bones, they can fossilize. Throughout their life, they deposit calcium salts in their skeletal cartilage to strengthen it. The jaws of a shark are heavy and solid; like bone. These same minerals allow most of the skeletal systems of sharks to fossilize quite well. Teeth have enamel, which is why they also appear in the fossil record.

They have good eyesight

Most sharks can see well in dark light areas; they have fantastic night vision and can even see colors. The back of shark eyeballs has a reflective layer of tissue called a mat. This helps sharks see very well in low light.

Shark skin is like sandpaper

We don’t know if you’ve ever touched a shark, but its skin is similar to the touch of sandpaper because it is made up of tiny tooth-like structures called placoid scales, also known as dermal denticles. These point towards the tail and help reduce friction from the surrounding water when the shark is swimming.

Since when do sharks exist?

Based on the fossil scales found in Australia and the United States, scientists assume that sharks first appeared in the ocean about 455 million years ago.

Blue sharks are really blue

The blue shark displays a bright blue color on its upper body and is usually snow-white underneath. Generally, most sharks are brown, olive, or grayish in color.

Not all sharks have the same teeth

Mako sharks have very pointed teeth, while white sharks have triangular and serrated teeth. Each leaves a unique and revealing mark on its prey. As a curiosity, a sandbar shark will have around 35,000 teeth throughout its lifespan. That awful!