Waddling, writhing, wandering, digging, laying eggs. There is no lack of verbiage when it comes to describing monotremes – the taxonomic order composed of only two animals, the platypus and the echidna. Revealing the countless strange things characteristics of these creatures are trope in news coverage – and it’s almost impossible to avoid, since they are mammals that lay eggs and sweat milk, among others bizarre features.
But perhaps the easiest way to outline the incredible evolutionary success of monotremes is to go straight to their DNA. A team of 40 researchers from Australia, China, Japan, Denmark and the United States did just that in a recent review of the monotreme genomes. Their findings are published in the journal Nature.
The first draft and analysis of the platypus genome sequence came in 2008. The recent article includes a highquality update of this sequence and the first echidna genome (for some reason, the echidna is always the second violin for the platypus) Interestingly, monotremes are halfway between oviparity and viviparity – referring to the place where the embryos are developed, in the eggs or in the parents’ body. This neither here nor there is reflected in the protein dependencies of animals.
“During the short egg incubation period, they kept one of the three main proteins in the egg that is used to make the yolk for chickens,” said Marilyn Renfree, a zoologist at the University of Melbourne and co-author of the study, in a press release, “but after hatching both the platypus and echidna have complex milk like other mammals to support their young during their long lactation.”
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Monotremes are a peculiar branch of the tree of life, as they help to fill in the gaps in our understanding of when animals with certain characteristics separate from each other.
“Actually, tThe platypus belongs to the Mammalia class. But genetically, it is a mixture of mammals, birds and reptiles, ”said Guojie Zhang, a biologist at the University of Copenhagen and co-author of the recent study, in a press release. “He preserved many of the original characteristics of his ancestors, which probably contributed to his success in adapting to the environment in which they live.”
And animals need that extra boost. Australian forest fires last year made efforts to track down the platypus more difficult as well as even more imperative. (A population was rescued and sent back to nature This summer.) Having the echidna genome sequenced will allow the genetic management of a threatened species in a similar way. After all, we cannot allow our strange and illustrious creatures to follow the path of tilacin and dodo.