Crabs make up 20 percent of all marine crustaceans caught and farmed worldwide, with over 1 Ѕ million tons being consumed annually.
Crabs are found in all of the world's oceans; there are also many freshwater and terrestrial crabs, particularly in tropical regions.
Crabs are omnivores, consuming both animal protein and plants.
About 850 species of crab are freshwater or semi-terrestrial species (Sternberg and Cumberlidge 2001).
The horseshoe crab, which also is called by the name king crab, is not a crustacean, and the hermit crab, although a crustacean, is not a true crab.
The earliest unambiguous crab fossils date from the Jurassic, although the Carboniferous Imocaris, known only from its carapace, is thought to be a primitive crab (Schram and Mapes 1984).
Crabs vary in size from the pea crab, only .25 inches wide, to the Japanese spider crab, with a leg span of 8 to 9 feet (Mann).
Some animals, including birds, reptiles, and insects such as bees, can see into a portion of the ultraviolet region (the "near ultraviolet" region).
Cracks make glaciers a dangerous place to visit, because they are not always easy to spot.
Crabs are omnivores, feeding primarily on algae, and taking any other food, including molluscs, worms, other crustaceans, fungi, bacteria and detritus, depending on their availability and the crab species. For many crabs, a mixed diet of plant and animal matter results in the fastest growth and greatest fitness.
A total of 10 eyes help the horseshoe crab get around. These eyes are distributed around the body including on top of its shell, on the tail and near the mouth to help orient the animal when swimming. Two compound eyes are easily seen on each side of the animal's shell.Mar 13, 2011