
Asian Scientist (Oct. 30, 2013) – Researchers have analyzed the genome of the Yangtze River dolphin (Lipotes vexillifer), revealing new insights into the evolutionary history of the dolphin. The study provides a valuable resource for studying the evolution and conservation of aquatic mammals.
The Yangtze River dolphin, known as baiji in China, was once regarded as the goddess of protection by local fishermen and boatmen in China. Unfortunately, this species has suffered huge losses in recent decades because of extreme pressures brought about by human activities.
Although efforts were made to conserve the baiji, it is now recognized as being functionally extinct. It is believed to be the first cetacean to be driven to extinction by human activity.
In this study, published in Nature Communications, the researchers completed a high-quality draft of the baiji genome and further re-sequenced three baiji using high-throughput DNA sequencing technology.
Their analysis of the baiji genome revealed that genes involved in oxidoreductase activity, ferric iron binding, metabolic processes and ATPase activity had undergone significant expansion, whereas genes involved in olfactory receptor activity decreased most significantly.
According to the researchers, these genetic changes may be evolutionary adaptations that allowed the baiji to live underwater by providing the ability to carry oxygen and sense objects underwater using echolocation (the ability to detect objects in the environment by sensing echoes from those objects).
Compared to all other mammalian genomes reported so far, researchers also found a significantly lower number of heterozygous single nucleotide polymorphisms (SNPs) in the baiji.
A reconstruction of the demographic history of the baiji indicated that this is likely due to a bottleneck occurring near the end of the last deglaciation, a time coinciding with a rapid decrease in temperature and a global rise in the sea level.
The article can be found at: Zhou et al. (2013) Baiji Genomes Reveal Low Genetic Variability And New Insights Into Secondary Aquatic Adaptations.
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Source: BGI; Photo: HBarrisonFlickr/CC.
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