![]() ![]() A new study published in September in the journal Developmental Dynamics lays this out the normal course of acorn worm regeneration.Īcorn worms are, as I wrote in October, made up of a proboscis which sits in a collar attached to a tail. Before scientists can begin breaking the worm’s genes to see what they do, however, they need to know what normal worm regeneration looks like. ![]() To that end, the scientists chose to study the acorn worm Ptychodera flava, whose regeneration you witnessed above. It may be possible to reactivate these regenerative molecular pathways in us using insights we gain from studying animals like the acorn worm whose gene networks are still operational. This matters because if regeneration was a trait present in the first animals and persisted a long time before groups like our own lost the ability, it is probable, the authors say, that humans still retain many or all of the genetic switches that control it, but they have been disabled somehow. Of course, that this seemingly magical ability exists among a group of animals so closely related to our own begs a more basic question: when did the ability to regenerate evolve? Was it an ability the first animals possessed and passed down to their descendants, or has it evolved multiple times in many different animal groups? That the earliest evolved living animals, like sponges, jellyfish, coral, and comb jellies, all have great powers of regeneration, suggests the former is true. Invertebrate genomes, like that of the acorn worms, lack duplication issues. But because there are so many different versions of the same gene to deal with in the vertebrates, the usual strategy is impractical. Normally, scientists amp up production of, suppress, or knock out a gene – effectively, breaking it - to study what the effect of that tinkering tells us about what the normal version does. That makes it much harder to tinker with their genetics for the purposes of studying regeneration. However, in a stroke of bad luck for scientists, the vertebrates that can regenerate have also, for unrelated reasons, had their genomes duplicated more than once. Fish and amphibians even regenerate parts of their central nervous systems. Lancelets, tunicates(sea squirts), frogs, fish, and salamanders can all regenerate parts of their bodies to one degree or another. Even among the chordates and vertebrates it is not uncommon. Sea stars and other echinoderms can famously regenerate large sections of their body should they be cut into pieces. Yet nearly every phylum of animals contains at least a few species able to regenerate. Unfortunately, that reality does not include us. “Popularized in myths, science fiction, and even horror movies, regeneration of missing and damaged tissue is a common reality in the animal kingdom,” the authors write. Regeneration is, perhaps surprisingly, not unusual among animals. This could obviously help a lot of people, should it pan out. They are suggesting we may be able to regenerate parts of our brains, central nervous systems, and perhaps even bodies that have been damaged or lost. I should emphasize, however, that these scientists are not suggesting humans can regrow entire heads. Those shared genes means that understanding how they can regrow the entire upper half of their bodies and central nervous system from scratch in a matter of just two weeks could help unlock doors that could produce radically better treatments for people with brain and spinal cord injuries, dementia, paralysis, and amputations. As such, they use many of the same developmental genes we use to develop our brains to grow their heads, “brains”, and bodies. They grow a hollow neural tube along their backs, just like us. But why should we care? Because these invertebrates are just about as close to being a chordate – an animal like ourselves with a dorsal spinal cord - as you can get without being one. OK, this is a cool party trick, you may concede. The images of regeneration go by a little quickly - try pausing and restarting the video to slow them down. ![]() Clearly, they need a better PR team).ĭon’t believe me? Here’s a time-lapse video that shows one accomplishing this show stopping feat in a mere two weeks: That animal is the acorn worm (This is the third time I have written about these humble and apparently vastly under-appreciated animals in just the last few months. ![]() But there is an animal – a close relative - that can do not only that, it can regenerate the entire front half of its body after bisection: head, heart, central nervous system and all. Humans have noted with frustration our conspicuous inability to regenerate organs, limbs, and heads. ![]()
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