Crabs are famous for their unique sideways walk. Scientists now believe this distinctive movement started about 200 million years ago, linking it to a common ancestor from the Jurassic period. A recent study published in eLife suggests this unusual trait may have given true crabs a survival edge.
The study is the most extensive to date on crab locomotion, combining behaviors observed in living species with evolutionary data. Researchers filmed 50 different species of true crabs for 10 minutes each. This allowed them to see how crabs move and where their movement originates in their evolutionary history.
Scientists found that true crabs (Brachyura), which comprise about 7,900 species, evolved to walk sideways likely only once. This contrasts with other adaptations seen in animal evolution, like the repeated transformations in body shape called carcinization. Sideways movement might have helped these crabs escape from predators by allowing for quick, unpredictable shifts. Yuuki Kawabata, an associate professor involved in the study, emphasized that this behavior could be a key reason for the ecological success of true crabs.
The study highlights that sideways locomotion is rare among animals but benefits crabs by enhancing their ability to avoid threats. However, developing this type of movement might also interfere with other essential activities, such as feeding and mating. Interestingly, while crabs are known for this unique locomotion, some related species still walk forwards.
Environmental changes, such as the breakup of Pangaea and shifts during the Mesozoic era, may have opened up new habitats for true crabs. This ecological opportunity likely fueled their diversification. The research indicates that understanding how behaviors evolve can shed light on the survival strategies of various species in changing environments.
The findings suggest a fascinating relationship between movement, adaptation, and survival. As researchers continue to explore animal behavior, we might discover even more about the innovative traits that have helped species thrive through the ages. For more detailed insights, you can check the study in eLife [here](https://doi.org/10.7554/eLife.110015.1).
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Ecology,eLife,Evolution,Evolutionary Biology
