The Origin of Worms

worms are truly ancient lineages of animals with evolutionary history stretching back over hundreds of millions of years various worm groupings have been inhabiting our world since long before the time of dinosaurs and the fact that they're still around today just shows how incredibly successful they've been now as you'll know if you saw our what is a worm video the name worm isn't really a scientific title that denotes a specific grouping of organisms that all share a common ancestor instead it refers to a type of body plan essentially anything that looks well well me as such when talking about the origin of worms we could be alluding to any number of different groups of animals that are vaguely worm-like in fact you could probably count some of the members of the Ediacaran faunas worms such as the basal animal dick and sonya which sort of looks like a polychaete the recently named Icaria or bizarre denizens of the burgess shales such as Hallucigenia which is actually related to the velvet worms but to avoid to this video going on forever and all kinds of evolutionary confusion we're going to stick to the origins of the three what could be considered main groupings of organisms we call worms today the annelids which includes earthworms bristle worms leeches and others the nematodes also called round worms and the platyhelminthes or flat worms plus we'll take a quick look at the end as a few other worm groupings that have a particularly interesting fossil record first though the annelids the evolutionary history of this group of worms can be traced back over 500 million years ago with ancient relatives being represented by fossils present in the famous middle Cambrian Burgess Shale of Canada about five hundred and eight million years old these include the species Canadia Spinoza and Burgess Akita Sethi Guerra both of which are fairly confidently agreed to be prehistoric members of the grouping poly kita within annelids though the actual classification of poly keets is a bit of a nightmare and it's likely that they're paraphyletic an unnatural evolutionary grouping but anyway there was also some debate amongst paleontologists as to whether the strange little were wack SIA from the Burgess Shale and other locations wasn't annelids too though more evidence seems to be mounting which suggests it's probably a mollusk a very interesting insight into annelid origins was published in 2018 when another one from the burgess shale was named undescribed Kootenai scolex which was so exceptionally preserved that even have attained potential neural and vascular tissues the first time this had happened in a fossil analyte even more significantly though it enabled paleontologists to work out how the annelid head evolved the bristles running down the sides of the animal called 'gta continue on to the head segment suggesting that the head of annelids actually formed from posterior more general segments of the body that over time specialized into this structure an interesting perspective into the developmental biology of annelid worms for a while before the discovery of Kootenay scolex it was thought that Canadia and burgess Okita were the oldest annelid worms known to science however even older annelids were discovered during the intervening years one probable an alert the pushed back the history of this group further was fragmented ah named in 2008 and based on fossils from lower Cambrian rocks in greenland about 518 million years old the paleontologists describing it placed it as a polychaete and noted that a had around 20 segments a straight gut drasil structures they seemingly used to propel themselves along the seafloor and no jaws possibly the oldest annelid currently known to science though is yelling gear have recently described ancient by latarian animal that dates to between 551 and 539 million years ago during the Ediacaran fossils of this species come from South China and traces of the trackways have also been discovered showing that this was one of the earliest animals that was capable of moving by itself and also exhibiting decision-making researchers can't be sure that this was definitely an analyte over suggesting that is either related to the annelids or pan arthropods nevertheless there's no doubt that if healing gear were alive today we'd cool a worm and it's amazing that this organism has had such significant implications for how we think about the history of life itself as it hints that complex animals were around in the Ediacaran and therefore the famous Cambrian explosion that occurred later may have been a less dramatic explosion of life than we thought anyway according to a 2007 study it wasn't until the Ordovician about 480 million years ago that the polic eat annelids started to properly diversify its during the early order vision that fossil annelid jaws start to appear in a record and so it's probably around them that the annelids Crown Group originated Oly koek eats the group including terrestrial earthworms then possibly originated sometime during the Mesozoic though there is some evidence suggesting an earlier beginning but this has been disputed so there's actually a pretty fascinating history to these worms early evolution but as with most things in paleontology many more fossils and studies will be needed before we can be more confident about how the annelids arose and it's still an ongoing area of research right then next we'll look at the nematodes this worm lineage is another absolutely ancient group of organisms and a truly fascinating phylum of animals I could make an entire video on nematodes themselves they're literally found everywhere in pretty much every environment on earth including inside humans it's been estimated that there are probably around 40,000 different species of nematodes and they're actually one of the most numerically abundant type of animal on the planet so prevalent that a 20-19 study calculated there to be around four point four times ten to the 20 nematodes in total across all top soils on earth that's a lot of worms so nematodes are clearly an important and ridiculously successful lineage of animals but when did they originate well since the majority of these worms are tiny microscopic and soft bodied creatures though there are exceptions such as the 13 meter long species that parasitizes the sperm whale it makes finding fossils of them very difficult however there are some indications of their presence in deep time amazing fossils of nematodes have been found preserved in amber from the Cenozoic but it's the more ancient fossils that provide better hints towards the group's initial evolution currently the oldest known nematode body fossils are specimens from Scotland that date to the early devonian about 396 million years ago they were found associated with a priest or a gland plant with clusters of eggs juveniles and adults all inhabiting the tissues of the plant indicating a very old parasitic relationship between nematodes and plants the still occurs today but this isn't the oldest evidence of nematodes in the fossil record since in early Ordovician rocks from China that date to about 470 million years ago there are tiny cylindrical burrows in prehistoric marine sediments that were most likely formed by these worms increasing the oldest known age of nematodes by over 70 million years and there's more fossils have been found in a remarkable Changjiang biota dating to the early cambrian around 518 million years ago that represent members of the related numata Morpho phylum indicating that since these relatives have been around since the Cambrian is likely that nematodes themselves existed then - and possibly lived even longer ago in the Precambrian as well indeed george poinar an expert on nematodes suspect that these animals potentially date back to as early as 1 billion years ago and we just haven't found the fossils of them yet so the nematodes also have a fascinating early evolutionary history represented by some pretty amazing fossils next where did the platyhelminthes the tapeworms and flat worms come from one of the oldest records of these worms in the fossil record is found in a shark coprolite fossilized feces from the Permian the specimen contains a total of 93 small smooth structures that are interpreted by the paleontologists as being the eggs of a tapeworm remarkably one of the eggs is even thought to preserve a developing larvae inside it and the morphology and pattern in which the eggs are deposited strongly indicates that they were laid by an ancient member of Sesto de the grouping that includes modern tapeworms so this discovery gives us some perspective as to the timeline of platyhelminthes evolution they seem to have been around at least 270 million years ago in the Permian however there is some more potential evidence for their existence before this time fossil hook structures found in much older Devonian rocks from Latvia might have originated from flat worms - these fossils are mostly associated with or actually attached to prehistoric placa durman a cathode Ian Fischer's indicating a parasitic lifestyle but the exact classification of what kind of parasitic organism can't be said for certain the hooks do look like those found in sess toads however it's also possible that they came from a different fire of parasitic worm a canvasser fala like the nematodes there are also some amazing fossil platyhelminthes that have been found preserved in san Amba such as a 40 million year old specimen in the order wrapped of sealer that retains developing eggs inside the body cavity the platyhelminthes are there for another pretty ancient and fascinating lineage of worms and I'm sure that future probably even older examples of these flat worms will eventually be discovered that continue to elucidate the origin of these organisms as we've already established a lot of different animal groups are called worms and these other lineages do sometimes have some interesting representatives in the fossil record one of these is the phylum Freya polida marine animals often referred to as penis worms I'll leave it to you to decide why they got their name there's a well-known extinct genus from the Cambrian best represented in the burgess shale of Canada called a Toya that is potentially a member of the stem group free up a leader though the exact relationships of this genus as well as many other of his relatives is a truly complicated mess the phylum Annika fora the velvet worms also has some interesting extinct members with the stem group potentially containing such creatures as Hallucigenia from the Burgess Shale as well as other equally weird animals including possibly micro dikteon and palsu podía from China though again the classification of these worms is still not entirely clear so there we have it the origins of some worms at least researching for this video has honestly been a wonderful experience the ancient evolution of worms is something I just never really given any thought to before but after having read about it I now see this is an absolutely fascinating topic I hope I've been able to pass on some of this fascination with prehistoric worms to you and I think it perfectly demonstrates how even the seemingly most humble of organisms can have a rich and extensive evolutionary history there's very much worth investigating and learning about and in some cases has profound implications for how we think about the very history of life on this planet anyway I hope you are enjoying worm week so far we've still got a lot more great worm videos coming so be sure to subscribe and spread the word a big thank you to our patreon supporters especially our dinosaur tear supporters corey peterson george fudge tech mayor's world nicole bueno pastor mark thorn dominic murphy and alex hawk if you would like to find out more about worms their history and the wonderful worms that surround us or please feel free to subscribe to the channel if you think we deserve it and if you would like to see more from us

Channel: Ben G Thomas

Views: 368,623

Rating: 4.9559727 out of 5

Keywords: Biology, Science, Paleontology, Palaeontology, Dinosaurs, Animals, Nature, Wildlife, Ben, Thomas, Prehistory, Anatomy, Fossil, Bones, News, 7Daysofscience, Days, of

Id: uUoTeob18QY

Length: 11min 20sec (680 seconds)

Published: Tue Jun 09 2020