Convergent evolution? Crown of Thorns starfish shows “surprising” chordate-like gene organization

_{Denyse O'Leary

December 17, 2014

Convergent evolution, Genomics, Intelligent Design}

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An intact Hox cluster. From ScienceDaily:

New research published in the journal genesis, by Kenneth Baughman, Dr. Eiichi Shoguchi, Professor Noriyuki Satoh of the Marine Genomics Unit at the Okinawa Institute of Science and Technology Graduate University, and collaborators from Australia, reports an intact Hox cluster in the Crown of Thorns starfish, Acanthaster planci. This surprising result contrasts with the relatively disorganized Hox cluster found in sea urchins, which are also echinoderms, classification of animals including starfish, sea lilies, and sea cucumbers. Stanford University Professor Christopher Lowe, who studies developmental biology in echinoderms, summarizes the paper: “The translocation of the Hox cluster in echinoderms has been a major red herring for understanding their evolution. It’s really good to have some hard data showing that some echinoderms exhibit some oddities that are not representative of all echinoderms.”

…

Generally, the Hox cluster shows “colinearity,” in which gene order correlates with the location of expression, or the developmental stage of expression. “For example, anterior Hox genes are expressed in regions that are closer to the head of an embryo, and are expressed sooner during development, versus the posterior Hox genes,” explained Baughman. “Thus, we were surprised to see chordate-like Hox cluster organization in starfish, which have a radial body plan.” Echinoderms are classical model organisms for embryology, and more recently evo-devo. Baughman added, “Interacting with the speakers and students of theOIST Winter Course ‘Evolution of Complex Systems’ (OWECS) allowed me to appreciate the importance of finding an intact Hox cluster in starfish.”

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By the way, it is a pretty remarkable life form anyway.

Comments

By combining evidence from fossils, genomic analysis, etc. in order to put together estimates of lineages. So, what kind of objective check are you looking for?AVS_{December 22, 2014
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Joe, If the genomes are of similar size, then they are closely related. If that doesn't work, then if the genomes are similar then they are closely related. If that doesn't work, then if some of the genome is similar then they are closely related. If that doesn't work, then if they look alike they must be closely related. If that doesn't work, they must be closely related. If that doesn't work, then it must be convergent evolution. Honestly, I get tired of explaining this evolution stuff to you over and over. You really need to pick up your game.Mung_{December 22, 2014
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How can you tell if they are related or not?Joe_{December 22, 2014
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If two organisms demonstrate similar structure/function relationships and these organisms are not closely related, then it is an example of convergent evolution. What kind of objective check would you be looking for?AVS_{December 22, 2014
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The funny thing is that evolutionists will never be able to define any actual limits to convergent evolution. To the evolutionist, whatever is deemed to have to have convergently evolved, convergently evolved. There is no objective check for such a thing. All they can do is endlessly speculate about an amount of convergence they personally feel would be unlikely. It's exactly the type of scenario one expects with pseudo-science.lifepsy_{December 22, 2014
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http://www.tolweb.org/Echinodermata http://www.differencebetween.com/difference-between-chordates-and-vs-echinoderms/Mung_{December 19, 2014
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wd400:
I can’t see how a radial adult arising holding on to a linear arrangement of hox genes is more or less surprising under evolution or ID.
But you can, of course, contact, email, the authors and ask them the reason for their surprise. Here's what I said:
Looking at their fossil remains, it would appear to be a body-plan formed by an iteration of the basic chordate plan. Unusual. But, since we’re dealing with the basic chordate plan, the linear array of Hox genes might not be such a surprise after all. However, this also might mean that its true phylogeny might lie outside of the echinoderm lineage.
I will translate, and leave it at that. It appears that in animals with a radial body-plan, the Hox genes are NOT in a linear order. In bilaterians and chordates, they are in a linear order. So, AFTER the rise of the echinoderms, you have an echinoderm exhibiting a radial body-plan, and its Hox genes ARE in a linear order. How can that be? Did the echinoderm pattern "converge" onto that of the chordates? Or, did the bilaterian body-plan, as I suggest, employ its linear order in a five-fold manner? Again, unusual. And, begging the question as to the phylogenetic roots of the starfish.PaV_{December 19, 2014
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bornagain77: perhaps you should buy and read Darwin’s Doubt, with an open mind, where the Ediacaran organisms, Jellies, and Sponges, are covered and shown to be non-ancestral to the Cambrian Biota We didn't reference jellies or sponges, but bilaterians. See Fedonkin & Waggoner, The Late Precambrian fossil Kimberella is a mollusc-like bilaterian organism, Nature 1997.Zachriel_{December 19, 2014
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Zach, perhaps you should buy and read Darwin's Doubt, with an open mind, where the Ediacaran organisms, Jellies, and Sponges, are covered and shown to be non-ancestral to the Cambrian Biota before just throwing these names out as if they explain Cambrian Explosion? If you don't want to, or can't afford to, buy it, , Dr. Paul Giem has done a chapter by chapter 'cliff notes' video series on the book here: Darwin's Doubt - Paul Giem - video playlist http://www.youtube.com/playlist?list=PLHDSWJBW3DNUaMy2xdaup5ROw3u0_mK8t The mysterious Ediacara biota, which also appeared abruptly before, or maybe alongside, the Sponges and Jellyfish, in the pre-Cambrian fossil record, largely disappeared from the fossil record a few million years before the Cambrian Explosion and thus are not seen to be viable as precursors to the Cambrian Explosion. Plant or Animal? Mysterious Fossils Defy Classification Excerpt: "Animals in the Ediacaran Period are almost universally bizarre, and it is very difficult to place them in any modern animal phyla," Xiao told LiveScience. http://www.livescience.com/12883-plant-animal-mysterious-fossils-defy-classification.html The Avalon Explosion: Excerpt: Ediacara fossils [575 to 542 million years ago (Ma)] represent Earth's oldest known complex macroscopic life forms,,, A comprehensive quantitative analysis of these fossils indicates that the oldest Ediacara assemblage—the Avalon assemblage (575 to 565 Ma)—already encompassed the full range of Ediacara morphospace. http://www.sciencemag.org/cgi/content/abstract/319/5859/81 Ediacaran embryos in retrospect - David Tyler - January 28, 2013 Excerpt: "there is currently no convincing evidence for advanced animals with bilateral symmetry in the Doushantuo biota". This particular quest for animals preceding the Cambrian Explosion has drawn a blank. Needless to say, Darwin's dilemma remains in full force. http://www.arn.org/blogs/index.php/literature/2013/01/28/ediacaran_embryos_in_retrospect Interestingly, 'soft-bodied' Jellyfish may have appeared in the fossil record a few ten million years before the Cambrian Explosion, and have remained virtually unchanged since they first appeared in the fossil record. Ancient fossilized Cambrian jellies compared to modern jellies – pictures http://qvcproject.blogspot.com/2012/08/the-joys-of-jellies_2.html Zach, I'll rest my case here, since I have much better things to do today than watch you chase your tail around in a circle.bornagain77_{December 19, 2014
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bornagain77: the trick is premised on “including as part of the Cambrian explosion (a) the origin of the Ediacaran organisms in the late Precambrian (which no serious scientist considers to be ancestral to the Cambrian animals) Bilaterian were extant in the Ediacaran.Zachriel_{December 19, 2014
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Darwinists continually try to down play the brevity of the main pulse of the Cambrian, refusing to be honest to just how problematic the Cambrian explosion actually is for Darwinism Undead: The Myth of the 80-Million-Year Cambrian Explosion - November 13, 2013 Excerpt: the trick is premised on "including as part of the Cambrian explosion (a) the origin of the Ediacaran organisms in the late Precambrian (which no serious scientist considers to be ancestral to the Cambrian animals), and (b) the small shelly fossils at the base of the Cambrian and (c) the main pulse of morphological innovation in the early Cambrian, and (d) subsequent diversification events right up until the end of the Cambrian period.",,, - Meyer notes that Marshall himself elsewhere excludes the precious small shellies.,,,- http://www.evolutionnews.org/2013/11/undead_the_myth079081.html A Graduate Student (Nick Matzke) Writes - David Berlinski July 9, 2013 Excerpt: Representatives of twenty-three of the roughly twenty-seven fossilized animal phyla, and the roughly thirty-six animal phyla overall, are present in the Cambrian fossil record. Twenty of these twenty-three major groups make their appearance with no discernible ancestral forms in either earlier Cambrian or Precambrian strata. Representatives of the remaining three or so animal phyla originate in the late Precambrian, but they do so as abruptly as the animals that appeared first in Cambrian. Moreover, these late Precambrian animals lack clear affinities with the representatives of the twenty or so phyla that first appear in the Cambrian. http://www.evolutionnews.org/2013/07/a_graduate_stud074221.html Dr. Stephen Meyer: Darwin's Dilemma - The Significance of Sponge Embryos - video http://www.youtube.com/watch?v=JPs8E7y0ySs What Types of Evolution Does the Cambrian Explosion Challenge? (Universal Common Descent & Gradual Change)– Stephen Meyer - video https://www.youtube.com/watch?v=AaF7t5wRFtA Moreover, Darwinists just assume the Cambrian explosion happened by unguided processes but have no detailed account how it is remotely plausible to happen by unguided processes: When Nature Resists: Explaining the Origin of the Animal Phyla - Paul Nelson - April 5, 2013 Excerpt: ,,,lately, I've run across something related to ontogenetic depth that is, well, mind-blowing. Since 1859, the origin of not a single bilaterian phylum (animal body plan) has been explained in a step-by-step (neo-Darwinian) fashion, where random mutation and natural selection were, as textbooks assert, the primary causal mechanisms. Take your pick of the phyla: Mollusca, Brachiopoda, Chordata, Arthropoda, you name it -- and go looking in the scientific literature for the incremental pathway, via mutation and selection, showing how that body plan was assembled from its putative bilaterian Last Common Ancestor. You'll be looking a long time.,,, http://www.evolutionnews.org/2013/04/paul_nelson_day070871.html Response to Critics - Meyer - Marshall - Part 1 https://www.youtube.com/watch?v=zqYUoRVswRY Response to Critics - Meyer - Marshall - Part 2 https://www.youtube.com/watch?v=Cg8Mhn2EKvQ Response to Critics - Meyer - Marshall - Part 3 https://www.youtube.com/watch?v=fR_Agl41TbE Moreover, there are 'yawning chasms' in the 'morphological space' between the phyla which suddenly appeared in the Cambrian Explosion,,, "Over the past 150 years or so, paleontologists have found many representatives of the phyla that were well-known in Darwin’s time (by analogy, the equivalent of the three primary colors) and a few completely new forms altogether (by analogy, some other distinct colors such as green and orange, perhaps). And, of course, within these phyla, there is a great deal of variety. Nevertheless, the analogy holds at least insofar as the differences in form between any member of one phylum and any member of another phylum are vast, and paleontologists have utterly failed to find forms that would fill these yawning chasms in what biotechnologists call “morphological space.” In other words, they have failed to find the paleolontogical equivalent of the numerous finely graded intermediate colors (Oedleton blue, dusty rose, gun barrel gray, magenta, etc.) that interior designers covet. Instead, extensive sampling of the fossil record has confirmed a strikingly discontinuous pattern in which representatives of the major phyla stand in stark isolation from members of other phyla, without intermediate forms filling the intervening morphological space." Stephen Meyer - Darwin’s Doubt (p. 70) Moreover, this top down pattern in the fossil record, which is the complete opposite pattern as Darwin predicted for the fossil record, is not only found in the Cambrian Explosion, but this 'top down', disparity preceding diversity, pattern is found in the fossil record subsequent to the Cambrian explosion as well. Scientific study turns understanding about evolution on its head – July 30, 2013 Excerpt: evolutionary biologists,,, looked at nearly one hundred fossil groups to test the notion that it takes groups of animals many millions of years to reach their maximum diversity of form. Contrary to popular belief, not all animal groups continued to evolve fundamentally new morphologies through time. The majority actually achieved their greatest diversity of form (disparity) relatively early in their histories. ,,,Dr Matthew Wills said: “This pattern, known as ‘early high disparity’, turns the traditional V-shaped cone model of evolution on its head. What is equally surprising in our findings is that groups of animals are likely to show early-high disparity regardless of when they originated over the last half a billion years. This isn’t a phenomenon particularly associated with the first radiation of animals (in the Cambrian Explosion), or periods in the immediate wake of mass extinctions.”,,, Author Martin Hughes, continued: “Our work implies that there must be constraints on the range of forms within animal groups, and that these limits are often hit relatively early on. Co-author Dr Sylvain Gerber, added: “A key question now is what prevents groups from generating fundamentally new forms later on in their evolution.,,, http://phys.org/news/2013-07-scientific-evolution.html “In virtually all cases a new taxon appears for the first time in the fossil record with most definitive features already present, and practically no known stem-group forms.” TS Kemp - Fossils and Evolution,– Curator of Zoological Collections, Oxford University, Oxford Uni Press, p246, 1999 “What is missing are the many intermediate forms hypothesized by Darwin, and the continual divergence of major lineages into the morphospace between distinct adaptive types.” Robert L Carroll (born 1938) – vertebrate paleontologist who specialises in Paleozoic and Mesozoic amphibiansbornagain77_{December 19, 2014
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Finding that starfish where not echinodrems would indeed be a huge surprise. But there is no evidence for such a proposition, and huge amount of evidence they are echinoderms, so I think we can disregard that. The rest of your comments seem to have very little to do with ID at all, just (not very well informed) phylogenetic thinking. I can't see how a radial adult arising holding on to a linear arrangement of hox genes is more or less surprising under evolution or ID.wd400_{December 19, 2014
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wd400: The tetrapods evolved from the lobe-finned fishes which date back to 395 mya. The starfish date back to 450 mya. Looking at their fossil remains, it would appear to be a body-plan formed by an iteration of the basic chordate plan. Unusual. But, since we're dealing with the basic chordate plan, the linear array of Hox genes might not be such a surprise after all. However, this also might mean that its true phylogeny might lie outside of the echinoderm lineage. We'll leave that to the experts. But this rearrangement of the tree of life would be, I think you'd have to admit, a "surprise." And again, to imagine using a basic plan five times over is not hard from the ID perspective.PaV_{December 19, 2014
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bornagain77 (quoting Wells): “The Cambrian Explosion was so short that it is below the resolution of the fossil record. It could have happened overnight. So we don’t know the duration of the Cambrian Explosion. We just know that it was very, very, fast.” Well, that's simply not the case. The Cambrian is divided into ten stages, with distinctive fossils in each stage. ETA: Furthermore, there is evidence in the Precambrian of metazoans.Zachriel_{December 19, 2014
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as to: "No one doubts that echinoderms descend from a bilaterally symmetrical animal" Seeing as echinoderms suddenly appeared in the Cambrian Explosion along with the other 20 or so phyla I certainly think there is more than enough room for someone, even wd400 himself, to 'doubt': "The first universally accepted echinoderms appear in the Lower Cambrian period,",,, It is hypothesized that the ancestor of all echinoderms was a simple, motile, bilaterally symmetrical animal http://en.wikipedia.org/wiki/Echinoderm 'hypothesis' is far from 'no one doubts' and the Cambrian Explosion is certainly NOT comforting for Darwinists! "The Cambrian Explosion was so short that it is below the resolution of the fossil record. It could have happened overnight. So we don't know the duration of the Cambrian Explosion. We just know that it was very, very, fast." Jonathan Wells - Darwin's Dilemma Quotebornagain77_{December 19, 2014
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It’s really good to have some hard data showing that some echinoderms exhibit some oddities that are not representative of all echinoderms. Mung: Amen to that! Finally, some hard proof that echinoderms evolved and weren’t just ‘poofed’ into existence.
Evolution predicts that observations will not line up with the theory. It's really good that we have some hard data proving that evolution was correct.Silver Asiatic_{December 19, 2014
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No one doubts that echinoderms descend from a bilaterally symmetrical animal. They are even bilaterally symmetric as larvae (perhaps the one thing I know about their developement). You'd have to be nuts to think they descended from a tetrapod, since they pre-date us by several hundred million years. So, no, I don't think ID is getting us anywhere here.wd400_{December 19, 2014
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wd400: Let me begin with this quote of RodW:
The fossil record shows that echinoderms used to be bilaterally symmetrical ( like most other organisms) and the common ancestor of echinoderms and chordates had bilateral symmetry (which requires a linear hox cluster) so they must have originally had their hox genes in a cluster. I
As I reflected on what the study discovered, and before RodW posted, here's how I began to think (BTW, this is how 'designers' think): Think of the tetrapod body-plan. Then think of a stick-man representation of a tetrapod: two lines verging from a center line, with two lines verging from the top of the center line, and then the 'head.' Well, this gives you 5 'lines.' So, the starfish could be an example of a tetrapod that has now changed its body-plan. But this would mean that the starfish would have descended from a tetrapod, or bilaterian, form. IOW, move the two 'arms' down from the top of the center line to the point where the two 'legs' meet the center line. Then move the 'head' down to the center of all of these intersections of lines. You have a starfish. So, you see, from an ID perspective, I judged that the fossil record should show that the starfish was descended from some bilaterian/tetrapod form, which is not what you would expect. This is what RodW explains above. I had to wait, however, to make sure that the Hox genes were, in fact, in a linear order for all of this to make sense given the assumption I've made. And, so, we have RodW's answer:
Yes they are in a linear order on the chromosomes.
Now take this "radial" pattern, and form a cylinder (i.e., layer upon layer), and, basically, you have echinoderms. It is possible that I have just explained the author's surprise. Am I wrong, or are Darwinists surprised, while IDists move off in the right direction? So, there's your answer.PaV_{December 19, 2014
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Whether or not starfish use the same hox gene order as vertebrates seems equally surprising or unsurprising under ID or evolution.
Yep. Entirely unremarkable. From the OP:
It’s really good to have some hard data showing that some echinoderms exhibit some oddities that are not representative of all echinoderms.
Amen to that! Finally, some hard proof that echinoderms evolved and weren't just 'poofed' into existence. From the OP:
Thus, we were surprised to see chordate-like Hox cluster organization in starfish, which have a radial body plan.
Starfish are lower on the tree of life than we originally thought. It's almost like finding a rabbit in the Cambrian. Now all we need to cap this off is a good just-so story! Anyone?Mung_{December 18, 2014
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I'm firmly in the ID camp, but if evolutionary theory puts starfish as members of a sister group to chordates then I have to agree with wd400: It wouldn't be a case of convergent evolution. Whether or not starfish use the same hox gene order as vertebrates seems equally surprising or unsurprising under ID or evolution.JoeCoder_{December 18, 2014
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wd400, I am not one of those folks who thinks ID ought to explain everything. For me, ID is quite limited in it's explanatory scope. Most of the objections to ID I see just make me yawn. I guess you could call me an ID minimalist. But I think I'm at least consistent because I am much the same the same way about evolutionary theory. It assumes too much and demonstrates too little in spite of it's grandiose claims. In the vast majority of cases, we just don't know enough to be certain. I would probably feel more at home over at The Skeptical Zone, but they aren't really skeptics over there. :)Mung_{December 18, 2014
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Pav, Yes they are in a linear order on the chromosomes. If you do a google search on 'hox cluster' you'll see a wiki entry for 'hox gene' with a pic...and the google images hit will have a bunch of pics of the clusters in various species. Vertebrates have 4 cluster ( I think some fish might have more) and Drosophila has one which has splitRodW_{December 18, 2014
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wd400: To answer your question, I need some more information from RodW.PaV_{December 18, 2014
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RodW: Thanks for the detailed information. When you speak of a "cluster," are you talking about a "cluster" that is in "linear" order? When I think of a cluster, a think of a kind of 'rounded' group of things.PaV_{December 18, 2014
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News and all, The results are surprising because in chordates, flies, worms and many other organisms the Hox genes are arrayed in a linear fashion with genes at one end specifying the head and the genes at the other specifying the tail. The genes are coregulated and so they need to be together in order. Echinoderms have radial symmetry so they dont need to have the hox genes in a cluster, although they'd still need them. The paper says that most echinoderms dont have them in a cluster but starfish do have them in a cluster. The fossil record shows that echinoderms used to be bilaterally symmetrical ( like most other organisms) and the common ancestor of echinoderms and chordates had bilateral symmetry (which requires a linear hox cluster) so they must have originally had their hox genes in a cluster. In most lineages the cluster has broken up. Its "surprising" that it hasnt in starfish. There must be some unique reason why its not been broken up in starfish- maybe a new function or contraint..but if the contraints arent too strong there maybe other starfish where its partially broken upRodW_{December 18, 2014
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I don't know how else I can say this. I know nothing about how development works in echinoderms, so I have no way of knowing whether this is suprising in far as development. But I'll ask you the same question: does this result surprise you given your belief in ID?wd400_{December 18, 2014
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Here's what the author said:
“Thus, we were surprised to see chordate-like Hox cluster organization in starfish, which have a radial body plan.”
wd400, haven't you oversimplified things by saying, "the result is that some echinoderms have a trait in common with hemichordates and chordates, which is the opposite of surprising."PaV_{December 18, 2014
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And how surprising is that finding to an IDer, Mung?wd400_{December 18, 2014
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Equally unsurprising is the result that some echinoderms have a trait not in common with hemichordates and chordates. Isn't evolutionary theory wonderful!Mung_{December 18, 2014
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News, you seem have mistaken "convergenceis everywhere" with "people keep on publishing press releases when they find a case of convergent evolution". In any case, to answer this one all you had to know was some intro to biology about how animals related to each other. As to the surprise. I don't know anything about development in echinoderms, so I had no expectation. Without that background, the result is that some echinoderms have a trait in common with hemichordates and chordates, which is the opposite of surprising.wd400_{December 18, 2014
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