Crabs first appeared on this Earth some 70 million years ago; they come in a vast number of different species, and are found everywhere, in all kinds of ecosystems--in the oceans, in lakes, in rivers and on land.
它們出現在地球的生命舞台七千萬年，種類繁多，無所不在。分佈在海洋、湖泊、河川、陸地等各種生態體系中。