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....Shellfish are aquatic invertebrates, that is also what it’s name means. Shellfish are cooked and eaten. They are crusteaceans, mollusks, and echinoderms. Shellfish are any saltwater invertebrate. Shellfish have the word fish in their name but they are not really fish. They are not fish because fish are not invertebrates. Ordinary fish are vertebrates and they call the ordinary fish "fish" because they need to tell them apart from shellfish. In the shellfish classes some do not include shrimp, crab, or lobster. Oysters, clams, mussels, winkle, and scallops are in the mollusk’s class and are eaten like the shellfish. Prawn, shrimp, lobster, and crabs are crustaceans that are eaten like the shellfish. Mollusks and crustaceans may be eaten like the shellfish, but echinoderms are not eaten like shellfish. Squid, octopus, cuttlefish and also terrestrial snails that are edible may be mollusks but they are only sometimes classified as shellfish. Eating shellfish may cause allergies. Humans have used shellfish in different ways for over one thousand years. In these days shellfish are made in many dishes. In Japan they use shellfish in sushi and also sashimi. They use eggs from the shellfish in the sushi and sashimi also. They are eaten raw or cooked.    
...Shrimp are decapod crustaceans that swim. You can find them in fresh water and also salt water. It is aquatic. They are caught and sold a lot to eat. They are prawns. Some crustaceans that share the name shrimp but are not even related to shrimp are the mantis shrimp and also the opossum shrimp and the mysid shrimp. The opossum and mysid shrimp are from the same class, which is Malacostraca and they are true shrimp. The Triops longiccaudatus and also the Triops cancriforms are popular in freshwater aquaria and are also sometimes called shrimp. The group they belong in is Notostraca, and that isn’t even related to the shrimp. They have similar prawns where their gills are but many people get confused with it and they call them prawns sometimes. Even sometimes prawns are also called shrimp. Shrimps are eaten as food. Prawns are of a distinct biological suborder of Decapod in biological terms of commercial farming and fishing. they are terms that are interchangeably for prawns and shrimp. Prawns are also sometimes used describe any big shrimp. Big shrimp are called jumbo shrimp. Wealthy countries like Australia use the word prawn only. Some shrimp are kept at home as a pet. Some of the shrimp are actually fancy. Some of the other shrimps remove algae and derbis. Freshwater shrimp that you can get as a pet is the Japanese Marsh Shrimp. It is also called the Amano Shrimp. The Amano Shrimp was pioneered by Takashi Amano. More freshwater shrimp you can get for a pet is the Cherry Shrimp, Ghost Shrimp, and also the Glass Shrimp. Saltwater fish that are popular are the Cleaner Shrimp, Fire Shrimp, and also the Harlequin Shrimp. 

....There are several groups of lobsters. One of them is the clawed lobster. These are not really related to the spiny lobster or the slipper lobster. They are really related to the reef lobsters. They are also not related to squat lobsters that much.
   These lobsters have a hard exoskeleton. They moult or to get a new exoskeleton to grow. When they are done eating, they start eating the old layer of their exoskeleton. Lobster live on muddy, sandy, and rocky bottoms. They normally live alone under rocks.
     Lobsters eat live food. They mostly eat fish mollusks, worms, and some plants. Some of them can live up to one hundred years. This makes them grow very big. Scientist do not know if lobsters feel pain or not.

..........Crabs are also crustaceans. Their abdomen is under their thorax. These creatures are covered with a thick exoskeleton. Crabs are omnivores. They sometimes eat algae. Other eat mollusk worms, fungi, and other crustaceans. A better diet for these fish is a mixed diet which are plants and other sea creatures.
     These creature morph to become an adult. Crabs make up 20% of all marine crustaceans caught. One and a half million are captured worldwide each year.

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