Nagasaki Univ.-Led Team Finds Crab Walk Dates Back 200 M. Yrs

Tokyo, May 24 (Jiji Press)–Crabs walking sideways originated from an ancestor that roamed the Earth some 200 million years ago, according to a team led by Yuki Kawabata, an associate professor of Nagasaki University’s Graduate School of Integrated Science and Technology. Crabs’ iconic lateral shuffle “has an advantage in escaping from predators, such as being able to move left and right quickly and making it difficult to predict escape directions,” Kawabata said. He suggested that the crabs’ evolution to adopt sideways walking may have helped the crustaceans diversify and succeed. The team recorded movements of 50 crab species–35 species that had adopted sideways walking and 15 species that walked forward. Comparing this data to the latest phylogenetic tree analyzed at a genetic level, the team aimed to deduce when the sideways walking had originated. The team said its analyses indicated that crabs evolved just once to sideways-walking animals about 200 million years ago during the Early Jurassic period from a forward-walking ancestor. Sideways walking has since been retained in a large number of crab species. It also said that during this time, conditions may have been perfect for crab diversification due to changes in the environment, such as the breakup of the supercontinent Pangea and the expansion of shallow water areas. Papers on the team’s findings were published in an international journal last month. END [Copyright The Jiji Press, Ltd.]