The cuttlefish and its relatives, squid and octopuses, often strike human observers as floating aliens wreathed in sucker-covered limbs — boneless, squirming appendages that would seem to have nothing in common with our own arms and legs.#Biology #Nature #Evolution #Genetics #Cephalopods
But hidden under the superficial differences, a new study shows, are some profound similarities: Human and cuttlefish limbs develop under the direction of the same genes. The new study, published on Tuesday in the journal eLife, lends weight to the theory that many animal appendages, from insect wings to fish fins, share a long evolutionary history.
It’s possible that the common ancestor of cuttlefish, flies and humans had limbs of some sort. Perhaps the animal used these genes to map the coordinates in other three-dimensional body parts, even one located entirely inside the body.
In later generations, animal lineages evolved profound differences. When it comes to limbs, flies and other insects are as different from cephalopods as they are from us. They have hard exoskeletons, with muscles pulling on them from the inside.
But every time a new kind of limb evolved, it seems, animals did not need a new way to tell cells where they were located inside it. Evolution reused the same genetic program over and over again.
“We’re looking at something ancient,” Dr. Cohn said.
Yonggang Nie and Fuwen Wei of the Chinese Academy of Sciences have spent years tracking wild pandas, analyzing exactly what kinds of bamboo they eat, and measuring the chemicals within those mouthfuls. And they found that the nutrient profile of a panda’s all-bamboo diet—very high in protein, and low in carbohydrates—is much closer to that of a typical carnivore than to that of other plant-eating mammals. “It was a surprise,” Wei says. Nutritionally, “bamboo looks like a kind of meat.”#Biology #Nature #Evolution #Pandas
In other words, “the giant panda does what human vegetarians do,” says Silvia Pineda-Munoz of the Georgia Institute of Technology. “We have high protein requirements, so we wouldn’t be able to survive if we just ate kale salad. Thus, we choose to eat tofu, beans, nuts, and other plant-based foods that compensate for the protein we aren’t getting from animal products. In the end, vegetarians and nonvegetarians don’t have such different diets when it comes to nutrients.” And so it is with China’s black-and-white bear.
This suggests that the move from meat to plants might have been easier for ancestral pandas than commonly assumed. By simply choosing parts of plants that are richer in protein, they could switch to vegetarianism without needing to radically overhaul their bodies. “If you’re going to switch to a specific plant, bamboo isn’t too bad, as it does have respectable plant protein levels, as well as a swath of different vitamins,” says Garret Suen of the University of Wisconsin at Madison.
These results should help to counter the tiresome myth that pandas are evolutionary dead ends: lazy, poorly adapted creatures that eat deficient diets, are inept at sex, and should be allowed to go extinct. Nonsense. Pandas have beautifully adapted to eat an extremely plentiful food source—bamboo—and they go to great, careful lengths to get exactly the right balance of nutrients.