Posted on 05/31/2005 12:03:06 PM PDT by PatrickHenry
In a stunning example of evolution at work, scientists have now found that changes in a single gene can produce major changes in the skeletal armor of fish living in the wild.
The surprising results, announced in the March 25, 2005, issue of journal Science, bring new data to long-standing debates about how evolution occurs in natural habitats.
“Our motivation is to try to understand how new animal types evolve in nature,” said molecular geneticist David M. Kingsley, a Howard Hughes Medical Institute investigator at the Stanford University School of Medicine. “People have been interested in whether a few genes are involved, or whether changes in many different genes are required to produce major changes in wild populations.”
The answer, based on new research, is that evolution can occur quickly, with just a few genes changing slightly, allowing newcomers to adapt and populate new and different environments.
In collaboration with zoologist Dolph Schluter, at the University of British Columbia, Vancouver, Canada, and Rick Myers and colleagues at Stanford, Kingsley and graduate student Pamela F. Colosimo focused on a well-studied little fish called the stickleback. The fish — with three bony spines poking up from their backs — live both in the seas and in coastal fresh water habitats all around the northern hemisphere.
Sticklebacks are enormously varied, so much so that in the 19th century naturalists had counted about 50 different species. But since then, biologists have realized most populations are recent descendants of marine sticklebacks. Marine fish colonized new freshwater lakes and streams when the last ice age ended 10,000 to 15,000 years ago. Then they evolved along separate paths, each adapting to the unique environments created by large scale climate change.
“There are really dramatic morphological and physiological adaptations” to the new environments, Kingsley said.
For example, “sticklebacks vary in size and color, reproductive behavior, in skeletal morphology, in jaws and teeth, in the ability to tolerate salt and different temperatures at different latitudes,” he said.
Kingsley, Schluter and their co-workers picked one trait — the fish's armor plating — on which to focus intense research, using the armor as a marker to see how evolution occurred. Sticklebacks that still live in the oceans are virtually covered, from head to tail, with bony plates that offer protection. In contrast, some freshwater sticklebacks have evolved to have almost no body armor.
“It's rather like a military decision, to be either heavily armored and slow, or to be lightly armored and fast,” Kingsley said. “Now, in countless lakes and streams around the world these low-armored types have evolved over and over again. It's one of the oldest and most characteristic differences between stickleback forms. It's a dramatic change: a row of 35 armor plates turning into a small handful of plates - or even no plates at all.”
Using genetic crosses between armored and unarmored fish from wild populations, the research team found that one gene is what makes the difference.
“Now, for the first time, we've been able to identify the actual gene that is controlling this trait,” the armor-plating on the stickleback, Kingsley said
The gene they identified is called Eda, originally named after a human genetic disorder associated with the ectodysplasin pathway, an important part of the embryonic development process. The human disorder, one of the earliest ones studied, is called ectodermal dysplasia.
“It's a famous old syndrome,” Kingsley said. “Charles Darwin talked about it. It's a simple Mendelian trait that controls formation of hair, teeth and sweat glands. Darwin talked about `the toothless men of Sind,' a pedigree (in India) that was striking because many of the men were missing their hair, had very few teeth, and couldn't sweat in hot weather. It's a very unusual constellation of symptoms, and is passed as a unit through families.”
Research had already shown that the Eda gene makes a protein, a signaling molecule called ectodermal dysplasin. This molecule is expressed in ectodermal tissue during development and instructs certain cells to form teeth, hair and sweat glands. It also seems to control the shape of - bones in the forehead and nose.
Now, Kingsley said, “it turns out that armor plate patterns in the fish are controlled by the same gene that creates this clinical disease in humans. And this finding is related to the old argument whether Nature can use the same genes and create other traits in other animals.”
Ordinarily, “you wouldn't look at that gene and say it's an obvious candidate for dramatically changing skeletal structures in wild animals that end up completely viable and healthy,' he said. "Eda gene mutations cause a disease in humans, but not in the fish. So this is the first time mutations have been found in this gene that are not associated with a clinical syndrome. Instead, they cause evolution of a new phenotype in natural populations.”
The research with the wild fish also shows that the same gene is used whenever the low armor trait evolves. “We used sequencing studies to compare the molecular basis of this trait across the northern hemisphere,” said Kingsley. “It doesn't matter where we look, on the Pacific coast, the East coast, in Iceland, everywhere. When these fish evolve this low-armored state they are using the same genetic mechanism. It's happening over and over again. It makes them more fit in all these different locations.”
Because this trait evolves so rapidly after ocean fish colonize new environments, he added, “we wondered whether the genetic variant (the mutant gene) that controls this trait might still exist in the ocean fish. So we collected large numbers of ocean fish with complete armor, and we found a very low level of this genetic variant in the marine population.”
So, he said, “the marine fish actually carry the genes for this alternative state, but at such a low level it is never seen;” all the ocean fish remain well-armored. “But they do have this silent gene that allows this alternative form to emerge if the fish colonize a new freshwater location.”
Also, comparing what happens to the ectodysplasin signaling molecule when its gene is mutated in humans, and in fish, shows a major difference. The human protein suffers "a huge amount of molecular lesions, including deletions, mutations, many types of lesions that would inactivate the protein," Kingsley said.
But in contrast, “in the fish we don't see any mutations that would clearly destroy the protein.” There are some very minor changes in many populations, but these changes do not affect key parts of the molecule. In addition, one population in Japan used the same gene to evolve low armor, but has no changes at all in the protein coding region. Instead, Kingsley said, “the mutations that we have found are, we think, in the (gene's) control regions, which turns the gene on and off on cue.” So it seems that evolution of the fish is based on how the Eda gene is used; how, when and where it is activated during embryonic growth.
Also, to be sure they're working with the correct gene, the research team used genetic engineering techniques to insert the armor-controlling gene into fish “that are normally missing their armor plates. And that puts the plates back on the sides of the fish,” Kingsley said.
“So, this is one of the first cases in vertebrates where it's been possible to track down the genetic mechanism that controls a dramatic change in skeletal pattern, a change that occurs naturally in the wild,” he noted.
“And it turns out that the mechanisms are surprisingly simple. Instead of killing the protein (with mutations), you merely adjust the way it is normally regulated. That allows you to make a major change in a particular body region - and produces a new type of body armor without otherwise harming the fish.”
He also said a fish is a fish is a fish.
Nope. You asked for a fish without armor.
I don't concede anything. From what did the snakehead evolve and can you prove this? As far as I know, the snakehead may always have existed as a snakehead or something very similar. My challenge is to show me something that exists as a fish today and tell me when THAT fish develops legs.
I guess you just don't get the point that I don't automatically assume that just because an existing creature has certain characteristics that it automatically is related to or evolved from another creature that may have some similar characteristics.
What I don't understand about you folks - you for example, is why you cannot simply accept my earlier proposition, which is to state that this is simply your BELIEF. There is nothing wrong with that and I don't care that you BELIEVE this. Other people BELIEVE other things - as you know, there are many people who believe that creatures such as the snakehead were specifically created, and that all the plants and animals that exist today basically always existed in their general form (aside from the relatively minor variations of size, color, armor or unarmored. That too, is a BELIEF and for all I know, maybe they're right. Maybe those folks who postulate that earth was seeded by aliens are right. Maybe someone else has another idea, perhaps evolution through catastrophe, that is "right". At this point, no one KNOWS what is "right". Therefore we should all state that these are beliefs. Personally I don't know how creation came about or how various species came into being. I simply say that....I don't know.
Actually...YES, that is how they treat each other by and large in the scientific world. Look up a man named Immanuel Velikovsky and see how he was treated for raising theories that were highly unpopular in the "scientific" world. The man was nearly hounded out of academia. What was his great crime? He attempted to correlate Bible history with events he believed occurred in the natural world and he had the temerity to back it up with abundant evidence. I can't speak for Velikovsky's ideas about the Bible, however I can say that his ideas about cataclysms affecting the earth and affecting the fossil record have been demonstrated abundantly since his books in the late 40s and 50s. Velikovsky postulated for example, that the massive extinctions may have been caused by gigantic meteors - at that time, an nearly inconceivable idea as most scientists ascribed to the theory that evolution, whether geological or biological was very slow and gradual. Read up on Velikovsky -as I say, I don't support everything he wrote, however, he is an excellent example of how scientific "heresy" is handled. Every generation has its dogmas.
copied from # 307.
I said "now if you could show a fish Genus that never ever had armor to develop it you would have a better case."
you seem to have forgotten the "develop it" part
You said a fish is a fish is a fish. Therefore, the snakehead is of the same kind as fish that lack legs and can't breathe air.
You need to work out what it is you want to say. You're extremely confused.
I guess you just don't get the point that I don't automatically assume that just because an existing creature has certain characteristics that it automatically is related to or evolved from another creature that may have some similar characteristics.
Yet you believe a porpoise is a mammal, even though it has fins, not legs, and swims in the sea.
As I said, extremely confused.
you seem to have forgotten the "develop it" part
No, the problem was, your sentence is ungrammatical, and I hadn't figured out what it was you were trying to say. My mistake; I should restrict myself to replying to posts written in English.
And you are extremely insulting. I guess you are not going to change my "confusion", as you put it, and I'm not going to improve your personality or debating skills, so let's agree to disagree.
well now that you know what I was trying to say, will you reply with full context answer? or will you belittle my grammatical skills for lack of an scientific example?
a not an...hahaaha
Some genes were turned off when they mutated and a stretch of the gene was lost. Some are inhibited.
I disagree. Had I called you a moron, a retard, or a ranting ignoramus, that would have been extremely insulting. I merely said you were confused. And it does seem you are confused. You want to claim a fish that does a few atypical things is not a fish, but a mammal that does a few atypical things is a mammal.
Nice catch, Vade. And hello and goodbye Ted. How many bannings will this be?
Your very terminology of calling me "confused" is a genteel insult. I am hardly confused. Readers can go back and read my posts and come to their own conclusions. But I am through with debating you. You have the mindset of a 15th century Jesuit debating how many angels can dance on the head of a pin. It would be pointless arguing with them as well. BELIEVE what you want, because that is all it is in the final analysis...a BELIEF.
If you are referring to me - I am not "Ted" now or in any other life. I am a female, in fact. I can assure you that more than one person has heard of or even read, Velikovsky. And it is very interesting that your way of dealing with this issue, even at this point, is to discuss "banning".
A better analogy would be the US F16 vs the stripped down F16's we sell to other countries. The US version is more advanced, but it didn't evolve from the foreign F16's. Rather the foreign F16's evolved from the more complex design.
*Department of Anthropology, 409 Carpenter Building, Pennsylvania State University, University Park, PA 16802; and Laboratory of Bioindustrial Informatics, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 981-8555, Japan
Communicated by Alan Walker, Pennsylvania State University, University Park, PA, June 17, 2004 (received for review March 18, 2004)
Mineralized tissue is vital to many characteristic adaptive phenotypes in vertebrates. Three primary tissues, enamel (enameloid), dentin, and bone, are found in the body armor of ancient agnathans and mammalian teeth, suggesting that these two organs are homologous. Mammalian enamel forms on enamel-specific proteins such as amelogenin, whereas dentin and bone form on collagen and many acidic proteins, such as SPP1, coordinately regulate their mineralization. We previously reported that genes for three major enamel matrix proteins, five proteins necessary for dentin and bone formation, and milk caseins and salivary proteins arose from a single ancestor by tandem gene duplications and form the secretory calcium-binding phosphoprotein (SCPP) family. Gene structure and protein characteristics show that SCPP genes arose from the 5' region of ancestral sparcl1 (SPARC-like 1). Phylogenetic analysis on SPARC and SPARCL1 suggests that the SCPP genes arose after the divergence of cartilaginous fish and bony fish, implying that early vertebrate mineralization did not use SCPPs and that SPARC may be critical for initial mineralization. Consistent with this inference, we identified SPP1 in a teleost genome but failed to find any genes orthologous to mammalian enamel proteins. Based on these observations, we suggest a scenario for the evolution of vertebrate tissue mineralization, in which body armor initially formed on dermal collagen, which acted as a reinforcement of dermis. We also suggest that mammalian enamel is distinct from fish enameloid. Their similar nature as a hard structural overlay on exoskeleton and teeth is because of convergent evolution.
Briefly; by comparing the genomes of bony fishes and other vertebrates, they identified SPP1 as the gene that regulates armor deposition in fish. SPP1 seems to have arisen by gene duplication in the teleost ancestor.
I guess this would be the wrong time to point out that the Jesuits were founded in 1540 . :-)
This is your problem, though. You make statements in support of your position, and when someone points ouit those statements are either hilariously wrong or hilariously contradictory, you try to pretend it doesn't matter. But in fact, once all the complete nonsense is stripped away, all you've posted can be reduced to one rant 'EVOLUTION IS A BELIEF, BECAUSE IS SAY SO!!!'. Your mind is made up, and facts confuse you.
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