As mentioned before,  most organisms a link or two down on the food chain rely on at least one defense mechanism to survive. Remaining unseen, looking toxic, and tooth-shattering carapaces are all relatively common on all fronts. The crab pictured above, photographed on Aswem Beach in Goa, relies on the first option – besides measuring under an inch across, it camouflages exceptionally well into the sand it scuttles across – and when feels threatened, dashes into hastily excavated boltholes. 

Others, such as this hermit crab, can just cover their vulnerable points in their scavenged shells.