Sea urchins are small spiny sea creatures of the class
Echinoidea found in oceans all over the world. (The name
urchin is an Old English name for the round spiny
hedgehogs sea urchins resemble.) Their shell, which is
also called the test, is globular in shape and covered
with spines. The size of an adult test is typically from
3 to 10 cm. Typical sea urchins have spines that are 1 to 3 cm in
length, 1 to 2 mm thick, and not terribly sharp. Diadema
antillarum, familiar in the Caribbean, has thin spines
that can be 10 to 20 cm long. Common colors include
black and dull shades of green, olive, brown, purple,
and red.
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short "tail" (Greek: brachy = short, ura = tail), or where the abdomen is entirely hidden under the thorax. They are generally covered with a thick exoskeleton, and are armed with a single pair of chelae (claws). Crabs are found in all of the world's oceans; there are also many freshwater and terrestrial crabs, particularly in tropical regions. Crabs vary in size from the pea crab, only a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 m [1].
The American lobster, Homarus americanus, is a species of lobster found on the Atlantic coast of North America. Within North America, it is also known as the northern lobster, Atlantic lobster or Maine lobster. It thrives in cold, shallow waters where there are many rocks and other places to hide from predators and is both solitary and nocturnal.
True shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Together with prawns, they are widely caught and farmed for human consumption.
