May 24, 2013
Researchers Solve The Mystery Of The White Tiger
April Flowers for redOrbit.com - Your Universe Online
Bengal tigers come in two distinctive colors: the bright, vibrant orange and black stripes, or pure white with black stripes. The white variety is only seen in zoos these days, but a new study from Peking University says they should be in the wild. According to the study, published in Current Biology, the white coats are produced by a single change in a known pigment gene."The white tiger represents part of the natural genetic diversity of the tiger that is worth conserving, but is now seen only in captivity," says Shu-Jin Luo of China's Peking University.
The research team advocates a proper captive management program to maintain a healthy captive population of both white and orange tigers. The scientists said it might be worth considering reintroducing the white variant into their wild habitat.
The genomes of a family of 16 tigers living in Chimelong Safari Park, including both white and orange individuals, were mapped by the research team. The complete genomes of three of the parents in the family were sequenced.
The genetic analyses led the team to the pigment gene SLC45A2, which has previously been associated with light coloration in modern Europeans and in other animals, including horses, chickens, and fish. In the white tiger, the variant primarily inhibits the synthesis of red and yellow pigments but has little to no effect on black. This explains why white tigers still show characteristic dark stripes.
Luo notes that historical records of white tigers on the Indian subcontinent date back to the 1500s. The last known free-ranging white tiger, however, was shot in 1958. That most white tigers were hunted as mature adults indicates that they were fit to live in the wild. The researchers say it is worth considering that tigers' chief prey species, such as deer, are likely colorblind.
Luo says that although captive white tigers do sometimes exhibit abnormalities, such as crossed eyes, any frailties are more than likely the fault of inbreeding. The team hopes to explore the evolutionary forces that have maintained tigers in both orange and white varieties.