By comparing bits of the platypus genome that were conserved with those that were lost, researchers can develop a clearer picture of what Jurassic mammals were like, and they can also determine what sorts of genetic traits contemporary mammals have gained and lost over the course of evolution. The truth about the platypus-and what makes the animal's recent genomic sequencing particularly interesting-is that it belongs to a lineage that separated from ours approximately 166 million years ago, deep in the Mesozoic era, and since that time, it has independently lost different elements of our last common ancestor. Using this line of reasoning, we humans could say with equal justification that we, too, are part reptile. Moreover, although one could say that the platypus is part reptile, it is so only in the sense that it is a member of the great reptilian clade that also includes prototherians, marsupials, birds, lizards, snakes, dinosaurs, and eutherian mammals (including humans). In reality, the platypus is not part bird, as birds are an independent and (directly) unrelated lineage. Unfortunately, such statements are inaccurate. One author, for instance, describes the platypus as a "genetic potpourri-part bird, part reptile, and part lactating mammal" (AFP, 2008). Over and over again, the article lead is that the platypus is "weird" or "odd," or even worse, that the animal is a chimera. So why the considerable ability to sense odors? The scientists speculate that it may involve sexual communication or the use of water-soluble odorants in navigating and hunting underwater.The recent publication of a draft of the platypus genome (Warren et al., 2008) has garnered a great deal of newspaper coverage, much of which has been misleading. As a primarily aquatic animal, the platypus was already known to rely on electrosensory receptors in its bill to detect faint electric fields emitted by underwater prey. ![]() One surprise was finding genes responsible for sensitive odor receptors. The platypus lacks nipples the young nurse through the abdominal skin. Of particular interest, the researchers reported, the analysis identified families of genes that link the platypus to reptiles (like those for egg-laying, vision and venom production), as well as to mammals (antibacterial proteins and lactation). Some repeated elements in the genome, the scientists noted, hold hints as to the chronology of changes in the platypus. The platypus shares 82 percent of its genes with the human, mouse, dog, opossum and chicken. In their investigation of the platypus genetic blueprint, the scientists found that its genome contains about 18,500 genes, similar to other vertebrates and about two-thirds the size of the human genome. “What is unique about the platypus is that it has retained a large overlap between two very different classifications, while later mammals lost the features of reptiles,” Dr. Greg Wood/Agence France-Presse - Getty Images The single subject of the study was a female platypus named Glennie, a resident of Glenrock Station in New South Wales, Australia, whose DNA was collected and analyzed.Ī platypus baby, or puggle, being held before being transferred back to its burrow at Taronga Zoo in Sydney, Australia. Warren, a geneticist at Washington University School of Medicine in St. The research is described in Thursday’s issue of the journal Nature by a group of almost 100 scientists led by Wesley C. If it has a bill and webbed feet like a duck, lays eggs like a bird or a reptile but also produces milk and has a coat of fur like a mammal, what could the genetics of the duck-billed platypus possibly be like? Well, just as peculiar: an amalgam of genes reflecting significant branching and transitions in evolution.Īn international scientific team, which announced the first decoding of the platypus genome on Wednesday, said the findings provided “many clues to the function and evolution of all mammalian genomes,” including that of humans, and should “inspire rapid advances in other investigations of mammalian biology and evolution.”
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