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The giant panda is a species that is instantly recognizable by its striking colors.
However, there are also a handful of giant pandas that are not black and white. These majestic creatures with brown-white fur live in a single mountain range in China. And now, according to new research, scientists may have solved the mystery of the extremely rare panda’s unusual fur.
The study, which involved examining the genetics of multiple pandas in the wild and in captivity, suggested that pandas with brown-white fur are the result of natural variation rather than a sign of inbreeding in a declining population.
The first brown panda known to science was a female named Dandan. In March 1985, a local ranger found the sick bear in Foping County in the Qinling Mountains of Shaanxi province. The panda was kept in captivity until his death in 2000.
Since Dandan’s discovery decades ago, 11 sightings have been reported, documented through official news sources or personal accounts shared with the authors of this latest study, published March 4 in the journal PNAS.
“Repeated instances of brown pandas imply that this trait may be heritable. But to date, the genetic basis underlying the brown-white fur color remains unclear,” the authors wrote.
senior author Dr. D., professor of wildlife ecology and conservation biology at the Institute of Zoology, Chinese Academy of Sciences. A better understanding of distinctive coloration could aid efforts to breed brown-white pandas in captivity, Fuwen Wei said. Beijing. According to the International Union for Conservation of Nature’s Red List of Threatened Species, the giant panda’s status as a species is vulnerable.
A panda family tree
To understand what lies behind this trait, researchers studied male brown panda Qizai, who was rescued as a cub from Foping National Nature Reserve in Hanzhong in 2009. He is currently the only brown panda kept in captivity.
Compared to hair samples from three black-and-white pandas under the microscope, Qizai’s brownish fur had fewer and smaller melanosomes; these melanosomes were small structures found in cells responsible for skin and hair pigment in mammals. What’s more, the study team found that melanosomes were more likely to be irregularly shaped.
The researchers then collected genetic information about Qizai and pieced together her family tree. Fresh feces, or bear feces, collected at the nature reserve has revealed the identity of its wild mother, a black-and-white female panda known as Niuniu who wears a tracking collar.
Researchers also identified Qizai’s son, a black-and-white panda born in captivity in 2020. (The study team then examined the genetics of a larger population to identify Qizai’s father, Xiyue, a black-and-white panda from the wild but tracked pandas.)
The scientists examined genetic information from Qizai’s family members and compared it with genetic information from 12 black-and-white pandas from the Qinling Mountains and 17 black-and-white pandas from other parts of China, using information from fecal and blood samples. .
Although none of Qizai’s immediate family members had brown fur, the researchers were able to show that his parents and son had one copy of the recessive trait on a gene known as Bace2, while Qizai had two copies.
An individual’s genes can carry recessive traits, such as blue eyes or red hair in humans, without them appearing as a physical trait. As with Qizai, each parent must have a copy of the genetic variant and pass it on for the trait to appear in the offspring.
Genetic analysis solves a puzzle
Thanks to analysis of a tissue sample preserved in ethanol for more than two decades, scientists were also able to sequence the genome of Dandan, the first known brown panda. Researchers found that Dandan also has the same recessive trait.
The scientists then performed a larger analysis on 192 black-and-white giant pandas to confirm that Bace2 was the gene responsible. The mutation that causes brown fur was present only in two pandas from the Qinling Mountains in Shaanxi, not in Sichuan province, where the majority of giant pandas in China live.
To confirm the findings, the scientists used the CRISPR-Cas9 gene editing tool to delete the genetic sequence they determined caused the mutation in the Bace2 gene in 78 laboratory mice. The change reduced the number and size of melanosomes in mice.
“The fur color of the knockout mice is light brown,” said Wei, who is also president of Jiangxi Agricultural University in Nanchang, China’s Jiangxi province.
“This proves that this deletion has the potential to change the fur color of a mouse, as the pigmentation pathway is relatively conserved (shared) among mammals. So it is very likely that this mutation affects the fur color of the brown panda.”
Natural diversity and inbreeding
It is unclear what causes the genetic mutation. This must be linked to the special environment of the Qinling Mountains, which has a different climate from Sichuan, Wei said. The genetic mutation does not appear to be a result of inbreeding, as once suspected, he said.
“It is more likely a result of natural variation rather than inbreeding. “Our kinship analysis shows that Qizai’s parents are not close relatives,” Wei added.
Tiejun Wang, an associate professor in the natural resources department at the University of Twente in the Netherlands, said the good news was that the unique coloration did not result from inbreeding. Wang, who studies brown pandas, was not included in the study.
Stating that he has worked as a ranger in the mountains for 10 years, Wang said, “This is a positive development for those interested in this species.”
Wang said he applauded the team “for their tremendous efforts to shed light on this scientific question.”
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