Pandas are anomalies of
evolution. They illustrate unusual evolutionary adaptations that may
have both helped and hindered survival. They are descendants of
meat-loving carnivorous bears, and their digestive systems are built to
process meat, yet they rarely eat it.
In fact, they eat almost nothing but bamboo. "Microbes Help Giant Pandas Overcome Meat-Eating Heritage," a nature.com story by Ewen Callaway, tells how these endangered creatures have evolved to live on plants.
contains protein, fats and sugars, but most of its nutrition is locked
in the cellulose fibers the make up the plant cell walls. Most
carnivores don't produce the enzymes necessary to digest cellulose.
Callaway describes the work of Fuwen Wei,
an ecologist at the Institute of Zoology at the Chinese Academy of
Sciences and his colleagues who studied microbes in the guts of giant
pandas. They found that the guts of wild and captive giant pandas
contained previously unknown genes produced by Clostridium bacteria,
which were similar to known genes for enzymes that break down cellulose.
The research is published in the Proceedings of the National Academy of Sciences.
|Ling-Ling and Hsing-Hsing, 1985|
1982 study of Ling-Ling and Hsing-Hsing, the two pandas the Chinese
government presented to President Richard Nixon in 1972 as a gift after
his visit to China, found that the pandas can't digest most of the
bamboo they eat - 92 percent of the cellulose and 73 percent of the
chemically similar hemicelulose passes right through their systems.
and colleagues say the newly discovered microbial enzymes may help the
pandas get extra energy from the bamboo they do process. He says the
microbes are "part of a suite of evolutionary adaptations" that include
powerful jaws and teeth and thumb-like bones in their paws that help
them grip the plant stalks.
A SciTech story by Chi-Chi Zhang
reports that pandas probably roamed the earth as long as three million
years ago, and says researchers believe pandas may have stopped eating
meat because mutations in their taste genes made them unable to
experience its flavor. Ruth Ley,
a microbiologist at Cornell University, is quoted in the Nature story
as saying the panda is pretty poorly adapted, because the main way it
gets its nutrients is to eat for 15 to 16 hours a day. The need to eat
almost constantly is apparently one of the reasons pandas don't hibernate like other bears. They can't pile on enough body fat to last for months.
Pandas are endangered
- only some 1,600 are known to live in the wild, mostly in China,
because of loss of habitat, poaching, and slow reproduction. Wild
pandas produce only one cub every two or three years, and captive
pandas reproduce even less.
Ling-Ling and Hsing-Hsing have both died after relatively long lives. The
Washington National Zoo has two more pandas from China, but this time
they weren't gifts. They arrived in 2000 under a 10 year $10 million loan agreement with China. The agreement was renewed in January 2011 so the Zoo can keep them another five years.