do they have any significance in culture?
Yes, both the constellation Cancer and the astrological sign Cancer are named after the crab, and depicted as a crab.
Crab
Both the constellation Cancer and the astrological sign Cancer are named after the crab, and depicted as a crab. 
where are the walking legs of crustaceans found UNANSWERABLE what are these type of creatures? They comprise of almost 67,000 described species, mostly small and their morphology varies greatly from the largest arthropod in the world – the Japanese spider crab to the smallest the 100-micrometre-long "Stygotantulus stocki". how do they mate? They reproduce sexually as the males decide which females to mate with by dietary differences. are they consumed ? Yes, mainly crabs, lobsters, shrimp, crawfish, and prawns. what are the first one? They are decapod crustaceans of the infraorder Brachyura.
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Crab [SEP] Cultural influences
Both the constellation Cancer and the astrological sign Cancer are named after the crab, and depicted as a crab. William Parsons, 3rd Earl of Rosse drew the Crab Nebula in 1848 and noticed its similarity to the animal; the Crab Pulsar lies at the centre of the nebula. The Moche people of ancient Peru worshipped nature, especially the sea, and often depicted crabs in their art. In Greek mythology, Karkinos was a crab that came to the aid of the Lernaean Hydra as it battled Heracles. One of Rudyard Kipling's "Just So Stories", "The Crab that Played with the Sea", tells the story of a gigantic crab who made the waters of the sea go up and down, like the tides.