{"id":602252,"date":"2026-04-23T20:30:18","date_gmt":"2026-04-23T20:30:18","guid":{"rendered":"https:\/\/www.newsbeep.com\/us\/602252\/"},"modified":"2026-04-23T20:30:18","modified_gmt":"2026-04-23T20:30:18","slug":"the-ancient-roots-of-the-crab-walk","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/us\/602252\/","title":{"rendered":"The Ancient Roots of the Crab Walk"},"content":{"rendered":"

Nature abhors a vacuum, but it loves a crab. The crab\u2019s wide, flat body plan has independently evolved multiple times in decapod lineages in a process called \u201ccarcinization\u201d (which you may know from the popular 2019 meme<\/a>). Oddly, even though crab-shaped decapods keep popping up in the family tree, the most famous crab innovation\u2014walking sideways\u2014seems to have evolved only once. That\u2019s according to a reviewed preprint published<\/a> in eLife.\u00a0<\/p>\n

So-called \u201ctrue crabs,\u201d or members of the infraorder brachyura, mostly scuttle sideways, but there are a few rebels who still tend to move forward and backward. \u201cDespite the rich information available on true crabs, data concerning their locomotor behaviors are sparse,\u201d study author Yuuki Kawabata of Nagasaki University said in a statement<\/a>. \u201cWhen did their sideways locomotion originate, how many times over the years did it evolve, and how many times did it revert?\u201d<\/p>\n

To find out, the research team selected 50 species of true crabs, placed them in a circular arena, and recorded their movements with an overhead video camera. After conducting a behavioral analysis, they determined 35 of the species moved sideways while 15 were forward-walkers and mapped the data onto existing crab family trees.<\/p>\n

Read more: \u201cAre Crabs Truly Crabby?<\/a>\u201d<\/p>\n

They discovered that sideways locomotion evolved only once from a forward-walking ancestor, but had remarkable staying power after that. \u201cThis single event contrasts starkly with carcinization, which has occurred repeatedly across decapod species,\u201d Kawabata said. \u201cThis highlights that while body shapes may converge multiple times, behavioral changes such as sideways walking can be rare.\u201d<\/p>\n

As for why this is the case, the researchers say sideways locomotion represents such a dramatic change it could interfere with other behaviors like burrowing, mating, and foraging.\u00a0<\/p>\n

The study also revealed that crabs got quite an assist from external events. According to the researchers, sideways walking evolved around 200 million years ago, right after the Triassic-Jurassic extinction. With so many ecological niches open and an expansion of shallow ocean habitats, the newly evolved crabs scuttled in to fill them.<\/p>\n

Again, nature abhors a vacuum, but it loves a crab. \"\"<\/p>\n

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Lead image: J. Antonio Baeza \/ Wikimedia Commons<\/p>\n","protected":false},"excerpt":{"rendered":"Nature abhors a vacuum, but it loves a crab. The crab\u2019s wide, flat body plan has independently evolved…\n","protected":false},"author":2,"featured_media":602253,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[51],"tags":[79,201],"class_list":["post-602252","post","type-post","status-publish","format-standard","has-post-thumbnail","category-wildlife","tag-science","tag-wildlife"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/602252","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=602252"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/602252\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/602253"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=602252"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=602252"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=602252"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}