Deep sea gigantism, also known as abyssal gigantism, is a phenomenon in which invertebrates and other deep-sea creatures grow to much larger sizes than their shallow-water counterparts. The giant Isopod is a famous example of deep sea gigantism, having a maximum weight of 1.7kg and strongly resembling a common woodlouse. Another example is the Japanese Spider crab which has the largest leg span of any arthropod, reaching up to 3.8 mitres and weighing up to 19kg. The reason why deep sea gigantism occurs is currently unknown, but it is hypothesised that the decreased temperatures of the deep sea may be responsible for creatures evolving to such large sizes by increasing cell size and life span.