why do pandas eat bamboo and not meat
Giant pandas are known for their voracious appetite for bamboo, but these furry mammals are actually meant to eat meat. That's at least according to a new study published in the journal, which details how the gut bacteria of giant pandas are not the type for efficiently digesting bamboo. Instead, they boast a carnivore-like gut microbiota predominated by bacteria such as
Escherichia/Shigella and Streptococcus, a team of Chinese researchers says. What's more, this evolutionary mishap doesn't just leave giant pandas chewing and eating bamboo all day, but it may even be leading them down the road to extinction. "Unlike other plant-eating animals that have successfully evolved, anatomically specialized digestive systems to efficiently deconstruct fibrous plant matter, the giant panda still retains a gastrointestinal tract typical of carnivores," lead study author Zhihe Zhang, director of the Chengdu Research Base of Giant Panda Breeding, China, said in a. "The animals also do not have the genes for plant-digesting enzymes in their own genome. This combined scenario may have increased their risk for extinction. " "This result is unexpected and quite interesting, because it implies the giant panda's gut microbiota may not have well adapted to its unique diet, and places pandas at an evolutionary dilemma," added study co-author Xiaoyan Pang.
Giant pandas evolved from bears that ate both plants and meat, researchers say, and started eating bamboo exclusively about two million years ago. These black-and-white bears spend up to 14 hours a day eating as much as 27. 5 pounds of bamboo leaves and stems. However, they can digest only about 17 percent of it. As a result, panda poop is mostly composed of undigested bamboo fragments, leaving scientists wondering how they digest even a little bamboo at all and receive nutrients from it. To find the answer and better understand panda gut microbiota, Pang and colleagues used a laboratory technique called 16S rRNA sequencing on 121 fecal samples from 45 giant pandas living in Zhang's Research Base. Their results showed that juvenile and adult pandas ate at least 22 pounds of bamboo and bamboo shoots each day, and 1. 1 to 1. 7 pounds of steamed bread. Despite their diet, these giant pandas possess extremely low gut microbiota diversity and an overall structure that is unique compared to other plant-eaters, and is actually more similar to carnivorous and omnivorous bears.
Unlike other herbivores, the giant panda gut did not harbor plant-degrading bacteria such as Ruminococcaceae and Bacteroides, but rather mostly the bacteria Escherichia/Shigella and Streptococcus. Panda gut microbiota also varied by season, with late autumn being quite different from spring and summer. The lack of bamboo shoots in late autumn could be an important factor, according to the researchers. Pang and his colleagues are planning to conduct further research on the matter, combining different scientific techniques to more fully understand the function of the panda's gut microbiota on the animals' nutrition and health. For more great nature science stories and general news, please visit our sister site, Headlines and Global News ( ). Everyone knows that pandas eat bamboo. But did you know that many of their closest relatives are carnivores? So how did the meat-eating ancestor of pandas become a vegetarian? According to this study, it may have had to do with the deactivation (technically known as pseudogenization )Pof an umami taste receptor gene.
Umami is the taste that makes things like meat, soy sauce, and mushrooms extra yummy. Apparently, at some point in panda evolution, the umami receptorPbecame non-functional. Based on how much the gene has changed, thePauthors calculate that this happened around the same time that pandas started eating bamboo. Whether it s cause or effect is unclear, although the authors think the switch to bamboo may have happened before the gene was lost. Regardless, the loss of the gene reinforced the panda s vegetarian diet because it made meat less deliciousPto the bears. PNow if only we could make chocolate less delicious wait, that s a terrible idea! Although it belongs to the order Carnivora, the giant panda is a vegetarian with 99% of its diet being bamboo. The draft genome sequence of the giant panda shows that its umami taste receptor gene Tas1r1 is a pseudogene, prompting the proposal that the loss of the umami perception explains why the giant panda is herbivorous. To test this hypothesis, we sequenced all six exons of Tas1r1 in another individual of the giant panda and five other carnivores.
We found that the open reading frame (ORF) of Tas1r1 is intact in all these carnivores except the giant panda. The rate ratio (y) of nonsynonymous to synonymous substitutions in Tas1r1 is significantly higher for the giant panda lineage than for other carnivore lineages. Based on the y change and the observed number of ORF-disrupting substitutions, we estimated that the functional constraint on the giant panda Tas1r1 was relaxed 4. 2 Ma, with its 95% confidence interval between 1. 3 and 10 Ma. Our estimate matches the approximate date of the giant panda s dietary switch inferred from fossil records. It is probable that the giant panda s decreased reliance on meat resulted in the dispensability of the umami taste, leading to Tas1r1 pseudogenization, which in turn reinforced its herbivorous life style because of the diminished attraction of returning to meat eating in the absence of Tas1r1. Nonetheless, additional factors are likely involved because herbivores such as cow and horse still retain an intact Tas1r1.
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