Platypus Genome Shows Mammal Evolution


Image: Klaus/Flickr

by Ashira Morris, ODP Staff Writer

Humans are now a step closer to understanding our strange fellow mammal the platypus. Scientists have published the most complete genome of these egg-laying, venom-producing, web-footed creatures, as well as the genome of their relative, the short-beaked echidna. Platypuses and echidnas are monotremes, a group that diverged from other mammals about 187 million years ago that’s unique in laying eggs then nursing their young. 

Why This Matters: Understanding the platypus gene can help us understand ourselves and other mammals better. Since the species branched off from our evolutionary trajectory so long ago, their features seem alien to us — but at one point, humans and platypuses had common ancestors. The more complete genome gives scientists and researchers a clearer map of how mammals evolved over time by looking at the DNA and proteins in the sequence. Looking at this branch in mammalian evolution can also help us understand the link between mammals and reptiles. For example: platypuses have the genes to produce the venom in their ankle spurs, similar to other reptiles but not present in other mammals.   

“In my opinion, among mammals, the platypus is the most fascinating species of all,” Wesley Warren told the New York Times. Warren, a professor of genomics at the University of Missouri, led a sequencing study in 2008. “They represent the ancestral state of what terrestrial mammal genomes could have been before adapting to various environments.”

Platypuses in the era of climate change: Platypuses have been swimming through Australia’s streams for millions of years, but human-induced climate change threatens their survival. Their population has dropped by an estimated 30% since Europeans arrived, but because people assumed they were common, there wasn’t adequate data collected on their populations for many years. People assumed that the population levels were “normal” even as the number of platypuses declined, a concept called shifting baselines. (Platypuses are also harder than other creatures to study: they are notoriously shy and most active at night.)

Now, platypuses face the ongoing threat of habitat loss coupled with rising temperatures and increasing wildfires. Researchers are looking into the impact of dams on the aquatic species; according to early results a poorly-managed dam can destroy the population of platypuses living above and below it. 

Last year, when Australia was ablaze, scientists rescued a small group of platypuses from their parched homes. A recent study estimates that the number of platypuses could decline further — by as much as 73% — in the next 50 years. Their case isn’t helped by Australia’s current Prime Minister Scott Morrison, who came to power by stomping on the prior leader’s energy plan to reduce emissions and has since championed pro-fossil fuel policies.  

 

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