Sea urchin Facts

Sea urchin Facts
Sea urchins are easily recognized type of marine animals. They belong to the group of animals called echinoderms. There are around 200 species of sea urchins that can be found in oceans throughout the world. Sea urchins usually live in warm waters on the rocky bottom or close to the coral reefs. Pollution of the ocean and overfishing (they are used for the preparation of sushi in Japan) are major threats to the survival of sea urchins. Due to drastic reduction in the number of sea urchins in the wild, they are placed on the list of threatened species (they can become endangered in the near future).
Interesting Sea urchin Facts:
Size of sea urchins depends on the species. They usually have 1.2 to 3.9 inches in diameter.
Sea urchins have globe-like shape of the body that is covered with large number of long spines. Bony plates form shell that provides protection for the soft inner parts.
Body of sea urchins has radial symmetry. That means that each sea urchin can be divided in five equal parts.
Color of sea urchins depends on the species. Majority of species are black, brown, purple, red or green in color.
Sea urchins have 5 rows of paired tube feet on the bottom side of the body. They end with suckers which facilitate adhesion to rocks, hunt and movement on the ocean floor.
Sea urchins have claw-like structures on the surface of the body, scattered among the spines. They are known as pedicellariae and their main purpose is protection against predators. Besides that, they are used for food collection and for the removal of the objects attached to the body.
Certain species of sea urchins (such as flower urchin) have spikes filled with venom.
Sea urchin has special type of mouth, called "Aristotle's lantern". Mouth is equipped with five sharp teeth that are able to drill a hole in the rock.
Sea urchins are omnivores (they eat both plants and animals). Sea weed, algae, plankton and decaying organic matter are usually on the menu of sea urchins.
Even though sea urchins have spines, they have a lot of predators. Main enemies of sea urchins are otters, sea birds, fish, crabs, sunflower stars and humans.
Mating season of sea urchins takes place in the spring.
Just like many other sea creatures, sea urchins reproduce by releasing eggs and sperm cells in the water. This type of reproduction is called external fertilization.
Fertilized egg undergoes larval stage before it becomes adult sea urchin. During the larval stage, sea urchin swims with other tiny animals as a part of zooplankton.
Most species of sea urchins live up to 30 years.
Red sea urchin has the longest lifespan on Earth. It can survive up to 200 years in the wild.

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