AsianScientist (Oct. 10, 2017) – Scientists in Japan have gained a deeper understanding of how snake venom evolved by sequencing the genome of a pit viper. Their findings are published in the journal Genome Biology and Evolution.
Globally, snake bites cause between 81,000 and 138,000 mortalities per year, according to the World Health Organization. More than 50 instances of snake bites were recorded in the past year on Okinawa alone, according to prefectural government figures.
A bite from a pit viper, locally known as habu, can cause permanent disability and even death. Yet, much about its venom remains an enigma. Highly variable in composition, even between littermates, this toxic cocktail keeps changing over generations.
In this study, scientists in Japan took samples of venoms and soft tissues from more than 30 specimens of the Taiwan (Protobothrops mucrosquamatus) and Sakishima (Protobothrops elegans) habus, invasive species on Okinawa, and sequenced their genomes to find out how the chemical composition of a snake bite evolves.
“For many years it was known that snake venoms evolve very rapidly, and the most common explanation for this has been natural selection,” said Associate Professor Alexander Mikheyev, the senior author on the paper and head of the Ecology and Evolution Unit at the Okinawa Institute of Science and Technology (OIST). “But there are reasons to suspect that this might not be the only evolutionary force at work.”
They found that in addition to natural selection, which optimizes the efficacy of the venom in the short term, genetic drift allowed more rapid turnover of individual proteins that make up the venom. This makes the venom more robust and widely effective, attacking crucial prey physiological systems, such as blood pressure or blood coagulation, at several points. Even if one venom component does not prove optimally effective, various others do.
“We’re only now coming up with analytical methods to look at venoms comprehensively,” said Dr. Steven Aird, the first author of the paper. “There’s a tremendous amount we can learn.”
The researchers’ work opens new doors in the field of evolutionary biology and may even have medical applications, such as the development of antivenoms and drugs.
The article can be found at: Aird et al. (2017) Population Genomic Analysis of a Pitviper Reveals Microevolutionary Forces Underlying Venom Chemistry.
Source: Okinawa Institute of Science and Technology Graduate University; Photo: OIST/Steven Aird.
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