Sea turtle

Sea turtles, sometimes called marine turtles, are special reptiles that live in the ocean. They belong to a group called Testudines and are part of 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 whether they are male or female when they are young. But as adults, you can tell the difference by looking at their tails. Male turtles have longer tails with a special opening near the tip, while females have shorter tails with the opening closer to the base.

Sea turtles have a special body shape that helps them swim well. Unlike land turtles, they cannot pull their heads and legs into their shells for safety. But their streamlined bodies reduce friction in the water, making it easier for them to glide through the ocean. The leatherback is the biggest sea turtle, growing up to more than 1.8 meters long and weighing as much as 640 kilograms. Other species are smaller, with the Kemp's ridley being the smallest.

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, with the exception of the leatherback sea turtle, which is in a different family called Dermochelyidae. The names of these groups come from an ancient word for tortoise.

Fossils show that sea turtles have been around since about 150 million years ago. Over time, they evolved special features to help them swim and eat. Their flippers, for example, changed from tools for moving to tools for catching food. Scientists study these ancient fossils to learn about how sea turtles lived long ago and how they are related to other turtles today.

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, depending on the type. 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, about 40 to 50 centimetres deep. She then puts between 50 and 350 eggs into the hole, depending on the type of turtle. After laying the eggs, she covers the hole 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 because they can move faster and avoid being eaten. Scientists have found that young turtles often spend time near floating seaweed called sargassum, where they can find food and shelter.

Physiology

Sea turtles need to stay balanced with the salt in the ocean. They have special glands that make salty tears to get rid of extra salt. This helps them stay healthy in the ocean water.

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, which helps them stand out. This might help them attract food, talk to each other, or hide from predators.

Ecology

Diet

Sea turtles eat a mix of plants and animals. Some, like the loggerhead, Kemp's ridley, olive ridley, and hawksbill, eat many different things such as small sea creatures, seaweed, sponges, and even land insects. Green sea turtles mostly eat sea grass when they are older, while leatherbacks eat jellyfish.

Relationship with humans

People around the world have hunted sea turtles for food and their shells. In the past, many places enjoyed eating turtle soup and using turtle shells for decorations. Some places still use turtle shells for making items like combs. However, many areas have changed to protect sea turtles. For example, in Tortuguero, Costa Rica, people now visit to see the turtles instead of hunting them, which helps keep the turtle populations safe.

Importance to ecosystems

Sea turtles help keep ocean grass healthy by eating it, which allows the grass to grow better. They also help beaches stay strong by laying eggs there, which provides food for plants and animals. The eggs and baby turtles that don't make it to the ocean help feed the 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, but more information is needed to fully understand how to help these amazing animals.

Symbiosis with barnacles

Barnacles are small creatures that attach 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.