2023-05-29 12:26:51
Round flat shell. The tail is tucked under the body. What a crab looks like, and what peak performance looks like — at least step by step development. The crab-like body plan has evolved at least five times among the decapod crustaceans, a group that includes crabs, crabs, and shrimp. In fact, it happens so often that it has a name: cancer.
So why did animals evolve into crab-like shapes? Scientists don’t know for sure, but they have a lot of ideas.
Carcinogenesis is an example of this phenomenon convergent evolution, when different groups develop the same traits independently. the same reason Both bats and birds have wings. But interestingly, the crab-like body plan appeared several times among the most closely related animals.
The fact that it occurs on such a microscopic level means that “evolution is fluid and dynamic.” Javier Lockea research associate in the Department of Zoology at the University of Cambridge told Live Science.
Related: Does evolution ever go back?
Crustaceans have changed from having a cylindrical body with a large tail—characteristic of shrimp or crabs—to a flat, rounded and stubby appearance, with a less prominent tail. As a result, many crustaceans that look like crabs, such as the delicious king crab beloved as a seafood delicacy, aren’t even technically a “true crab.” They adopt a crab-like body plan, but in fact they belong to a closely related group of crustaceans known as “false crabs.”
When a trait appears in an animal and persists through generations, it is a sign that the trait is favorable for the species—a fundamental tenet of natural selection. Crayfish-like animals come in many sizes and thrive in a wide range of habitats, from the mountains to the deep sea. He said their diversity makes it difficult to narrow down a common feature to their body plan Joanna WolfHe is a research associate in organic and evolutionary biology at Harvard University.
Wolfe and his colleagues offer some possibilities in a 2021 paper in the journal Life articles. For example, the folded tail of a lobster is prominent in lobsters, which reduces the amount of vulnerable flesh that predators have access to. The flat, rounded shell allows the crab to spread more laterally than the cylindrical body of the lobster.
But Wolf said more research is needed to test these hypotheses. He’s trying to use genetic data to better understand the relationships between different crustacean decapods, to determine when different “crab” lineages evolved, and to isolate cancer-causing agents.
Another possible explanation: “Cancer doesn’t have to have a body, it might be the result of something else in the organism,” Wolf said. For example, a crab body plan might be so successful not because of the shape of the shell or the tail, but because of the possibilities that the shape opens up for other parts of the body, said Luke, co-author of the 2021 paper with Wolfe.
For example, the tail of a giant lobster propels the animal into the water to help crush prey. That can get in the way and limit other aspects, Luwick said. The lobster’s body shape may allow the animals to develop specialized roles for their legs beyond walking, allowing the crabs to adapt more easily to new habitats. Some crabs have adapted their legs for digging under sediment or wading through water.
“We think the crab’s body plan evolved independently several times due to the animals’ versatility,” Locke said. “This allows it to go places that other crustaceans can’t.”
The crab-like body outline has also been lost several times during evolution – a process known as decarcinogenesis.
“Crabs are flexible and versatile,” Luke explained. “They can do a lot of things back and forth.”
Wolf thinks of crabs and other crustaceans like Lego creations: they have many different elements that they can change without significantly altering other features. So it is relatively easy to make a cylindrical shape flat or vice versa. But for better or worse, humans aren’t turning to crabs anytime soon. “Our body is not stereotyped like that,” Wolf said. “[Crustaceans] The right building blocks are already in place.”
1685365115
#animals #turn #crabs
