Written By: Peter Whiting
Marine animals live in water-filled places all over the world. These animals have adapted in different ways so that they can live at different depths, in different water temperatures, and in places with little or no light. There's a lot more than just fish and boats in the ocean: You'll find animals with shells, animals that look like plants, and even animals that are mammals just like humans.
Shellfish
Shellfish are sea creatures that have exoskeletons. That means that they have their skeletons on the outsides of their bodies! Shellfish aren't actually fish; they're more closely related to insects than fish. Most people are familiar with shellfish because people eat them. If you've ever eaten shrimp or clams, you've eaten shellfish.
- Shellfish are food for humans and for other marine animals.
- Clams, mussels, oysters, and scallops are all types of shellfish.
- People catch shellfish using a type of ship called a fishing trawler.
Corals
Corals are little, boneless animals that grow in a tube-like shape called a polyp. Coral polyps root themselves close together in one place, like plants do, and then they create exoskeletons out of limestone. Over time, this limestone builds up to make a coral reef. Some corals are coral-colored, but many more are brown, green, or red.
- The open end of a coral polyp is a mouth ringed by tentacles. The tentacles use stinging cells to catch food.
- Corals in shallow, warm water let algae live inside of them. The algae makes food using photosynthesis, and the coral eats some of this food. Meanwhile, the algae stays safe inside of the coral, where other animals can't eat it.
Marine Mammals
Marine mammals, like other mammals, are warm-blooded, have lungs that they use to breathe air, and have hair. Marine mammals are grouped into four types. Cetaceans include whales and dolphins; pinnipeds include sea lions and seals; sirenians include dugongs and manatees; and marine fissipeds include sea otters and polar bears.
- There are 129 different species of marine mammals.
- Polar bears are thought to have evolved from brown bears during the Pleistocene Epoch.
- Dugongs are sometimes called sea cows because they mostly eat sea grass.
Sea Turtles
There are seven different types of sea turtle species in Earth's oceans. Although sea turtles come ashore from time to time to lay eggs or bask in the sun, they spend most of their time in the ocean. Five species are considered endangered: olive ridley, green, leatherback, loggerhead, and hawksbill turtles.
- Sea turtles enjoy eating jellyfish.
- An average sea turtle can hold its breath underwater for up to five hours.
- They are not able to retract into their shells like other turtles.
Fish
The five oceans on Earth are home to around 20,000 different species of fish. These fish come in a variety of colors, sizes, and shapes. They live in different temperatures and depths.
- The Atlantic cod can grow up to 6.5 feet long and eventually weigh around 200 pounds.
- The blue banded goby lives in the Pacific Ocean. It is small and brightly colored and depends on the reefs where it lives for protection and food.
- The three-spot damselfish lives in the coral reefs of the Gulf of Mexico and the Caribbean Sea. Young damselfish are bright yellow and often have blue dots, while adult damselfish are greenish-brown in color.
Seabirds
Seabirds have adapted to live on or near the water. They typically live longer and produce fewer babies than other types of birds. As a result, they spend a lot of time raising the babies they do produce. They are also known for their long migrations.
- Some seabirds spend part of the year far away from the ocean.
- Most seabirds are able to grab prey underwater.
Sharks and Rays
Sharks have been one of the main types of predators in the world's oceans for most of history. More than 450 different species of sharks exist. However, about 25% of the shark population is currently endangered. One reason is that they are harvested for their fins. Sharks range in size from less than a foot long to more than 40 feet long! Rays are related to sharks, but they are smaller and flatter.
- The blue-spotted ribbontail ray lives in the Indian and Pacific oceans. These rays feed off of the ocean floor. Their name comes from the blue spots on their bodies.
- The lemon shark lives in the mangrove forests and coral keys of the Atlantic Ocean. It is a large, powerful shark. Fishing boats often go out in search of these sharks, which are prized for their meat and fins.
- The southern stingray lives in the western Atlantic Ocean. It spends the majority of its life on the seafloor, picking up food with its mouth, which is located on the bottom of its head.
Additional Resources
- Bearded Seal: Oceana provides pictures and information about the bearded seal and many other species on their site.
- California Sea Lion: Sea lions are part of a group of marine animals called pinnipeds.
- Giant Octopuses: Some of the biggest octopuses in the world live near the West Coast of the United States.
- How Will Changing Ocean Chemistry Affect the Shellfish We Eat? The National Oceanic and Atmospheric Administration looks at how the ocean is becoming more acidic and what that might do to scallops, oysters, and clams.
- Basic Information About Coral Reefs: The Environmental Protection Agency discusses the different types of coral reefs and the dangers they face.
- How Many Fish Live in the Ocean? Scientists believe that around 3,500,000,000,000 fish live in the ocean.
- Information About Sea Turtles: Female sea turtles return to land to lay their eggs, but many male turtles never go back to the shore after they hatch and enter the sea.
- Ocean Habitat: The amount of salt in the water and the temperature help to determine what types of plants and animals can live in different parts of the ocean.
- Life on the Ocean Banks: The Great Cormorant: Some animals that rely on the oceans to survive live on the shore, like the great cormorant, a type of bird.
- Scientific Classification: Sharks and Rays: Scientists have lots of ways to define what makes sharks, rays, and whales different from each other.
