Crab

In Southeast Asia, mud crabs (Scylla serrata) are cooked with chilli peppers to make the "sweet, yet savoury" chilli crab. In Goa and Mozambique, crab curry is a typical dish, flavoured with chilis, garlic, coconut, and spices. For the British dish dressed crab, the crab meat is extracted and placed inside the hard shell. In the Chesapeake Bay region of Maryland, crab meat is mixed with mayonnaise, mustard, and breadcrumbs to make crab cakes. Crabs can be made into a bisque, a smooth, creamy, seasoned soup of French origin. Crab sticks, also called surimi, are made from minced fish meat that is crafted and colored to resemble crab meat. It is a popular sushi ingredient in Japan and South Korea.

True crabs typically walk sideways (hence the term crabwise), because of the articulation of the legs which makes a sidelong gait more efficient. Some crabs walk forward or backward, including raninids, Libinia emarginata and Mictyris platycheles. Some crabs, like the Portunidae and Matutidae, are also capable of swimming, the Portunidae especially so as their last pair of walking legs are flattened into swimming paddles.

Brachyuran crabs are mostly active animals with complex behaviour patterns such as communicating by drumming or waving their pincers. Crabs tend to be aggressive toward one another, and males often fight to gain access to females. On rocky seashores, where nearly all caves and crevices are occupied, crabs may also fight over hiding holes.

True crabs attract a mate through chemical (pheromones), visual, acoustic, or vibratory means. Pheromones are used by most fully aquatic species, while terrestrial and semiterrestrial crabs often use visual signals, such as fiddler crab males waving their large claws to attract females. The vast number of brachyuran crabs have internal fertilisation and mate belly-to-belly. For many aquatic species, mating takes place just after the female has moulted and is still soft. Females can store the sperm for a long time before using it to fertilise their eggs. When fertilisation has taken place, the eggs are released onto the female's abdomen, below the tail flap, secured with a sticky material. In this location, they are protected during embryonic development. Females carrying eggs are called "berried" since the eggs resemble round berries.

True crabs make up 20% of all marine crustaceans caught, farmed, and consumed worldwide, amounting to 1.5 million tonnes annually. One species, Portunus trituberculatus, accounts for one-fifth of that total. Other commercially important taxa include Portunus pelagicus, several species in the genus Chionoecetes, the blue crab (Callinectes sapidus), Charybdis spp., Cancer pagurus, the Dungeness crab (Metacarcinus magister), and Scylla serrata, each of which yields more than 20,000 tonnes annually.

In some species, meat is harvested by manually twisting and pulling off one or both claws and returning the live crab to the water in the knowledge that it may survive and regenerate the claws.