A team of researchers in Japan says they found that crabs’ sideways walk originated around 200 million years ago from a common ancestor.
The study was published by a group of scientists from Nagasaki University and other institutions. They say it could help people understand how animals’ ways of moving have evolved.
The research involved 50 species of crabs placed in a plastic “circular arena” that matched their native environment.
The researchers shot videos of the crabs for a period of 10 minutes each and checked whether they moved sideways or forward.
They then integrated data collected with a recent phylogenetic framework. They say their analysis revealed that sideways walking evolved only once from a forward walking ancestor and has since been largely retained.
In the era when crabs are thought to have started walking sideways, shallow waters extended due to the break-up of continents. The researchers say the new environment may have created favorable conditions for crabs to diversify.
They say sideways movers enjoyed advantages related to predator avoidance, as their escape direction is made unpredictable thanks to their ability to move quickly in either lateral direction.
The team’s leader, Associate Professor Kawabata Yuuki of the Graduate School of Integrated Science and Technology at Nagasaki University, describes crabs’ sideways walk as very strange behavior. He said the sideways movement is extremely rare.
He added that he thinks the study’s results will lead to finding out how this revolutionary way of movement affected the success of living things.