A starfish is a marine animal with thick arm like extensions sticking from it's body. A starfish can have up to 40 extensions but never less than five. All starfish bodies consist of a round disc like body and arm like extensions. The mouth is located on the underside of the body. The mouth leads to a bag like stomach. The stomach has grooves that extend from the mouth to the tip of each arm. On each arm are small tube like feet that help in walking. In some species of starfish there are suction cups on the arms as well. Each of the arms have an eye spot. This eye spot doesn't see but senses light instead. One of the most interesting facts about starfish is that they do not have a brain.
Starfish are found in shallow water in the Atlantic, Indian and Pacific Oceans. They live in kelp-forest, rocky coast lines, coral reefs, sandy ocean bottoms and tide pools.
Starfish eat shelled animals like sea urchins, oysters, and mussels. Once the starfish locates its prey, it will attach itself to the shell and pry it open. Once the shell is opened the starfish will turn its stomach inside out and put it inside the shell. The stomach will then digest the animal inside its shell. When the animal is digested the starfish sucks the stomach back into its body and the digested substance is sucked up through one of the arms.
Starfish are preyed upon by sharks, manta rays, and large bony fish. Large starfish will occasionally eat smaller starfish too. To escape predators they may drop their arms off: The removed arm then will soon be replaced by a new arm. Even if the starfish is cut in half another half will replace the missing one creating two identical starfish.
The Manta Ray is the largest ray . It can be 19 feet long and weigh 2,300 pounds. Some manta rays have been caught that measure an incredible 23 feet across! The manta ray, a.k.a. " The Devilfish " is one of the gentlest creatures in the sea. They are so gentle that they are known to let themselves be petted and let humans ride them. The manta looks like a large blanket as it floats peacefully in the water. For this it is appropriate that the word "manta" means blanket. The manta lives mainly in tropical water bodies and swims with another manta. At times the manta jumps clear out of the water.
It has a skeleton made of cartilage, and its nose, mouth, and gills are on the bottom.
Manta rays give birth to live young called pups. When their babies are born, they are closed in their mini wing flaps.
Another member of the rays, the stingray, is very dangerous. Famous for it's powerful, poisonous sting. Its sting is often deadly to the victim. the stingray has a flat , diamond-shaped body with large flapping "wings". They vary in size and weight. Some of the big ones measure 13 feet across and weighed several hundred pounds. Stingrays live mainly among coral reefs in the Indian and Pacific Oceans.
One of the most beautiful and mysterious looking fish in the sea is the eagle ray. Its back has a dot pattern ranging in color from white, yellow, and green. The design helps the ray to hide from attackers. Its bottom is white and its tail that is sometimes two times longer than its body, is black. Its skeleton is cartilage. Its wings can measure up to 71/2 feet across, and it can weigh 500 pounds. The eagle ray is a good hunter as it is very sensitive to smells in the water. The eagle ray lives in the Atlantic Ocean and Caribbean Sea.
Along the the western coast of North America from Oregon to California, bat rays live in reefs, on sandy bottoms and in ocean mud. The bat ray has a large head and two long pectoral fins that look like a bat. Most bat rays are black or brown and can be 5 feet wide and weigh up to 200 pounds. The bat ray is like the manta in that it can be seen swimming along in schools, it can jump out of the water and skim across the surface for several and its skeleton is made of cartilage.
You can call sea urchins the porcupines of the sea. Like a porcupine quills sea urchins count on their long spines to deter hungry predators. You can pick up most sea urchins without getting hurt except for the long spined sea urchins found in South Florida. Their poisonous sharp spines can stab into human skin and break off. In cooler waters up north more harmless sea urchins like the purple and green cannot hurt you.
Sea urchins belong to the phylum echinodermata, the same group as sea lilies, sea stars, sea cucumbers and sand dollars. Although, difficult to see through all the spines sea urchins also have a hard outer body like it's relatives. Their outer skeleton called the test is made up of ten fused plates that encircle the sea urchin like the slices of an orange.
Every other section has holes which the sea urchin can extend its tube feet. These feet are controlled by a water vascular system. By changing the amount of water inside the animal can extend and contract its feet to move around. Sea stars move about the same way. Mainly, sea urchins use their feet to hang on to the bottom of the ocean or whatever it is on while feeding. Rut, they can move fast walking on their feet, their spines or even their own teeth.
When a sea urchin dies, all the spines fall off, leaving only the rest. Which is the hard outer layer. If you look carefully at the outer shell you can see small bumps covering it Where the spines where once connected. The base of the spine used to fit over the bump like a snug cap. The spines can rotate a variety of ways around this bump. In a live sea urchin the skin and muscle cover the outer layer and can be pulled on to move the spines.
Sea Urchins eat by a mouth structure called Aristotle's Lantern. It is made up of five hard plates that come together like a beak. They use their beak-like mouths to scrap algae clean off the rocks. This scrapping can wear down the plates so the sea urchins teeth grow to replace the worn down ones. Their mouth is located on the bottom of their body. While any waste are excreted through the top part of the animal.
Sea Urchins mainly live in groups in colder offshore waters, but sometimes travel into shallow waters to look for food. The green sea urchin is usually found in tide pools, and below the low tide line. They also tend to shy away from light. Their outer layer grows to a size of 1-4 inches.