Sea turtle

Sea turtles, also called marine turtles, are special reptiles that live in the ocean. They are part of a group called Testudines and belong to the suborder Cryptodira. There are seven kinds of sea turtles today: the flatback, green, hawksbill, leatherback, loggerhead, Kemp's ridley, and olive ridley.

Five of these seven sea turtle species are in danger of disappearing forever, according to the IUCN Red List of Threatened Species. The flatback turtle, which lives only in the waters of Australia, Papua New Guinea, and Indonesia, is one of the two species that is not in immediate danger.

Sea turtles can be divided into two groups based on their shells. Most have hard shells and are called cheloniids. The leatherback turtle is the only sea turtle with a leathery shell, and it belongs to the group called dermochelyids.

Description

Sea turtles look the same when they are young, whether they are male or female. But as they grow up, you can tell the difference by looking at their tails. Male turtles have longer tails, while females have shorter tails.

Sea turtles have bodies shaped for swimming. Unlike land turtles, they cannot pull their heads and legs into their shells. But their bodies are streamlined, which helps them glide easily through the water. The leatherback is the largest sea turtle, growing more than 1.8 meters long. Other species are smaller, like the Kemp's ridley.

Taxonomy and evolution

Sea turtles are part of a group of animals called turtles, which also includes land turtles and tortoises. Most sea turtles belong to a family called Cheloniidae, but the leatherback sea turtle is in a different family called Dermochelyidae.

Fossils show that sea turtles have been around for about 150 million years. Over time, they changed to better swim and eat. Their flippers, for example, changed from tools for moving to tools for catching food. Scientists study these old fossils to learn about sea turtles from long ago.

Distribution and habitat

Sea turtles live in all oceans except near the poles. The flatback sea turtle is only found along the northern coast of Australia, while the Kemp's ridley sea turtle lives only in the Gulf of Mexico and along the East Coast of the United States.

These turtles usually stay near the edges of continents in shallow water. In their early years, they float among seaweed in the open ocean, with green sea turtles especially liking Sargassum patches for food and shelter. As they grow older, they move closer to shore, and females come onto sandy beaches to lay eggs.

Sea turtles travel long distances to reach their nesting beaches. Their large size helps them move far and protects them from ocean predators like sharks. In 2020, fewer humans around because of the COVID-19 virus led to more sea turtle nests in places like Thailand and Florida. Less plastic and light pollution may have helped them.

Life cycle

Sea turtles take about 10 to 20 years to grow up and become adults. Once they are grown, they can travel thousands of miles to find places to have babies. After meeting up with a partner in the water, the mother turtle comes back to the beach to lay her eggs. Some turtles return to the very same beach where they were born.

When a female turtle is ready to lay eggs, she usually comes onto the beach at night. She digs a hole in the sand with her flippers. She then puts eggs into the hole and covers it with sand and leaves the beach, returning to the ocean. The eggs are left alone and will hatch on their own.

The eggs take about 50 to 60 days to hatch. Once they hatch, the baby turtles dig their way out of the sand and go straight into the sea. Most baby turtles hatch at night, but some types hatch during the day. Larger baby turtles are more likely to survive. Scientists have found that young turtles often spend time near floating seaweed called sargassum, where they can find food and shelter.

Physiology

Sea turtles have special glands that make salty tears. This helps them stay balanced with the salt in the ocean.

Sea turtles can control their body temperature in different ways. Some, like leatherback sea turtles, can keep their bodies warmer than the water around them. Others, like green sea turtles, sometimes come out of the water to bask in the sun.

Sea turtles breathe air and have lungs, so they need to come up to the surface to get oxygen. They can stay underwater for a long time, from a few minutes while looking for food to many hours while sleeping. They can quickly refill their lungs when they surface.

Sea turtles can also glow in the dark! Scientists found that some sea turtles can produce a special light, called fluorescence.

Ecology

Diet

Sea turtles eat both plants and animals. Some turtles, like the loggerhead, eat small sea creatures, seaweed, sponges, and even land insects. Green sea turtles mostly eat sea grass when they are older. Leatherbacks eat jellyfish.

Relationship with humans

People have hunted sea turtles for food and their shells. In the past, many places ate turtle soup and used turtle shells for decorations. Some places still use turtle shells to make items like combs. But now, many areas work to protect sea turtles. For example, in Tortuguero, Costa Rica, people visit to see the turtles instead of hunting them. This helps keep turtle populations safe.

Importance to ecosystems

Sea turtles help keep ocean grass healthy by eating it. This helps the grass grow better. They also help beaches stay strong by laying eggs there. The eggs and baby turtles that don’t reach the ocean help feed plants that keep the sand in place.

Conservation status and threats

Many sea turtle species are in danger because of things like fishing nets, bright lights on beaches, and plastic in the ocean. People are working hard to protect them.

Symbiosis with barnacles

Barnacles are small creatures that stick to sea turtle shells. They get food as the turtle swims, but they can make it harder for the turtle to swim by adding extra weight.