Leatherback sea turtle

The leatherback sea turtle, known scientifically as Dermochelys coriacea, is a remarkable marine reptile. It is the largest living turtle species on Earth. It also holds the title of the heaviest non-crocodilian reptile.

Unlike most other turtles, it does not have a hard, bony shell. Instead, it possesses a flexible carapace covered in oily flesh and leather-like skin. This unique structure gives the turtle its common name. This species is the only living member of the genus Dermochelys and the family Dermochelyidae. Because of its unique anatomy, it is easily distinguished from all other modern sea turtles.

The leatherback's shell is a masterpiece of biological engineering. It lacks the hard scutes found on other turtles. Instead, the skin contains embedded, tiny bone pieces called osteoderms. These osteoderms are made of hydroxyapatite and collagen tissue. They have jagged edges often called teeth. These pieces are connected by a configuration of interpenetrating extremities known as sutures. These sutures create flexible joints in a zig-zag pattern. This design allows the carapace to move both in and out of plane. This flexibility is vital for survival. It allows the carapace to expand when the turtle breathes in air. It also allows the shell to contract when the turtle dives deep into the ocean.

This structure helps the turtle withstand the high hydrostatic pressure of deep dives.

Physiologically, the leatherback is built for life in the open ocean. It has a highly hydrodynamic, teardrop-shaped body. This shape reduces drag as it moves through the water. The turtle uses two large front flippers for propulsion. These flippers are the largest in proportion to body size among all living sea turtles. They lack claws and are adapted for efficient swimming. To eat, the leatherback does not use teeth. Instead, it has points on the edges of its upper lip. It also has backwards-pointing spines inside its esophagus. These spines help the turtle swallow prey and prevent it from escaping.

Leatherbacks are also unique among reptiles for their ability to manage body temperature. They can maintain high body temperatures even in cold water. This is achieved through several specialized features. They have an extensive covering of brown adipose tissue, which is a type of fat. They also use countercurrent heat exchangers. These are systems in the flippers and around the trachea that help retain warmth. While some thought they had a high resting metabolism, recent studies suggest a different method. Leatherbacks maintain heat through a very high activity rate. They may spend as little as 0.1% of their day resting. This constant swimming creates heat within their muscles.

The history of the leatherback is well-documented by scientists. Domenico Agostino Vandelli first named the species in 1761. He originally called it Testudo coriacea. In 1816, the French zoologist Henri Blainville created the genus name Dermochelys. Later, Leopold Fitzinger established the family Dermochelyidae in 1843. Evolutionarily, leatherbacks are very ancient. Their relatives have existed since the Cretaceous period, over 110 million years ago. The leatherback family split from other sea turtle families approximately 49 to 70 million years ago.

These turtles have a massive global distribution. They are found in all tropical and subtropical oceans. Their range even extends into the Arctic Circle and as far north as Norway and Alaska. They can be found as far south as New Zealand and South Africa.

Some adults grow to incredible sizes. A verified specimen found in Pakistan measured a large curved carapace length. In the Atlantic, the Mayumba National Park in Gabon is a major site. Nearly 30,000 turtles visit these beaches every year. However, the species faces significant challenges. Global nesting populations are declining. In 1980, an estimated 115,000 females nested annually. Recent estimates show only 26,000 to 43,000 females nest each year.

Leatherbacks are true champions of the deep sea. They are among the deepest-diving marine animals in the world. They have been recorded diving to depths of 1,200 meters.

Most of their dives last between 3 and 8 minutes. However, they can occasionally perform much longer dives of 30 to 70 minutes. They are also incredibly fast swimmers. One record from the Guinness Book of World Records listed their speed at 35 km/h. This makes them the fastest-moving reptiles in the ocean. Their ability to dive deep and swim fast allows them to follow their prey, such as jellyfish, across vast distances.