Researcher shows how cone snails developed poison gland from spare gut parts

May 20, 2011 by Bob Yirka report
Conus geographicus (a marine snail) Credit: Kerry Matz/National Institute of General Medical Services

(PhysOrg.com) -- Canadian Louise Page, associate professor at the University of Victoria, BC, has solved a mystery that has perplexed zoologists since early 19th century naturalists first wondered if venomous cone snails might have developed their poison producing glands through evolution of their esophagus somehow; speculation that of course led many to wonder if that were so, how did the snail continue with swallowing and digesting its food.

Cones as they are known colloquially, are a of snails that use a small tube to shoot harpoon-like teeth connected to a radula (a spaghetti like string) through a proboscis at suspecting to stun or kill it; they then haul their prey back to them and devour it, spitting out the parts they don’t like. The snail can turn and point the proboscis (which looks sort of like a cartoon version of a tiny elephant’s trunk) at its prey and after loading a tooth with poison launch it’s "harpoon" by forcefully contracting muscles, situated at the base of the . Some estimates put the number of different species of cone snails in the neighborhood of six hundred or so, of varying sizes and coloring; though most are pretty little, some can grow to as long as 23 centimeters (about nine inches) and pack sufficient punch to kill a human being.

Page found the answer in Hawaii, home of the cone snail species Conus lividus, where, as she describes in her paper in Proceedings of the Royal Society B, she grabbed a mass of eggs, took them back to her lab and set about hatching and raising them. Along the way she singled out specimens during different stages of their development (when they were still larvae) fixed them with chemicals and sliced them up and photographed them to see what was going on. She then fed the whole batch of photos into a computer program that allowed her to watch as the larvae developed, and was then able to see that the cone snail originally has two sets of digestive tracts, one of which develops into the venom gland. Mystery solved.

Page explains that the process is known as modular evolution, whereby a species develops a trait over time without disrupting other important bodily functions, something that has been seen in a wide range of other animals and insects.

Explore further: Reptile Database surpasses 10,000 reptile species

More information: Developmental modularity and phenotypic novelty within a biphasic life cycle: morphogenesis of a cone snail venom gland, Proc. R. Soc. B, Published online before print May 18, 2011, doi: 10.1098/rspb.2011.0501

Abstract
The venom gland of predatory cone snails (Conus spp.), which secretes neurotoxic peptides that rapidly immobilize prey, is a proposed key innovation for facilitating the extraordinary feeding behaviour of these gastropod molluscs. Nevertheless, the unusual morphology of this gland has generated controversy about its evolutionary origin and possible homologues in other gastropods. I cultured feeding larvae of Conus lividus and cut serial histological sections through the developing foregut during larval and metamorphic stages to examine the development of the venom gland. Results support the hypothesis of homology between the venom gland and the mid-oesophageal gland of other gastropods. They also suggest that the mid-region of the gastropod foregut, like the anterior region, is divisible into dorsal and ventral developmental modules that have different morphological, functional and ontogenetic fates. In larvae of C. lividus, the ventral module of the middle foregut transformed into the anatomically novel venom gland of the post-metamorphic stage by rapidly pinching-off from the main dorsal channel of the mid-oesophagus, an epithelial remodelling process that may be similar to other cases where epithelial tubes and vesicles arise from a pre-existing epithelial sheet. The developmental remodelling mechanism could have facilitated an abrupt evolutionary transition to the derived morphology of this important gastropod feeding innovation.

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210
1 / 5 (2) May 20, 2011
" her to watch as the larvae developed, and was then able to see that the cone snail originally has two sets of digestive tracts, one of which develops into the venom gland. Mystery solved."
PART of the mystery is solved!
WHY did the snail ADAPT to serve its energy needs in this manner. Did things get crowded? SO the venom is defensive as well as aggressive energy grab - like a small firm that is attractive to predatory big ones so it swallows a 'poison pill' that makes it unsavory (after many other firms have been swallowed of course) while using the leverage/debt/poison to aggressively compete in a niche where it is under-sized, perhaps? HOW did it know that it was a meal on another's table. How does a species transmit threat sensitivity across its genome? How does it choose a response or how does the threat trigger a response. I say again, evolution IS adaptive..evolution IS after the fact change. This snail became different to LIVE: Seek the adaptive trigger.
word-to-ya-muthas
210
1 / 5 (1) May 20, 2011
Further, did this change in the digestive system entail chemical change to the digestive juices? That may even be easier to ascertain if we can examine several specimen across time and the snail genome. Then the question becomes, If there was chemical change, how did it know what chemicals to change to? To eat plants or microbes, such a proposed change does not appear to be needed; But as I suppose, the move was an energy play, the snail may have been symbiotic maybe, maybe even parasitic at one time with another player.
The only evident parallel I can see, please help me here, is if prey and predator were all in the same, relative environment; warm, saltwater, isolated and something triggered, or forgot to prevent, -gasp- cannabalism -gasp, whereupon we would get both breeding/mating pressure and genome selection AT WARP SPEED! (Like lactrodectus)
Many creatures have failed evolution's test: The need to adapt to a living planet's changes.
word-to-ya-muthas
aroc91
3 / 5 (2) May 21, 2011
@210

Evolution doesn't have a goal. It's not a conscious entity. The mutations that don't kill the animal before it reproduces are passed on. It's as simple as that.
210
1 / 5 (2) May 21, 2011
@210

Evolution doesn't have a goal. It's not a conscious entity. The mutations that don't kill the animal before it reproduces are passed on. It's as simple as that.


No, your solution/thought IS SIMPLE and I am sure you are comfortable with that, but the dynamism of evolution suggests adaption. Adaptation and the mechanisms of adaptation were my point and you addressed NONE OF THEM...and your solution...simple.
Here: http://www.physor...616.html
and here: http://news.natio...ion.html
"There IS more of heaven and earth than dreamt of in our philosophy" do not purchase, hook, line, and sinker, the notions your textbooks sell you. If they were always correct, there would be no new textbooks!
Reproduction, evolution, and mutation have constraints to their expression IF not, every reproductive act would fail due to unbridled mutation! No, something is guiding them, resisting cascade failure.
word-to-ya-muthas
Ethelred
4 / 5 (4) May 22, 2011
Adaptation and the mechanisms of adaptation were my point and you addressed NONE OF THEM...and your solution...simple.
He addressed them. It really is that simple. There ARE mutations. There IS death due to the environment. Mutations that help are conserved. Mutations that hurt are selected out by DEATH.

! No, something is guiding them,
Yes. The environment. Nothing else is needed nor is there any evidence that anything is involved.

Reproduction, evolution, and mutation have constraints to their expression
Yes. Death. And repair mechanism.

IF not, every reproductive act would fail due to unbridled mutation!
Bullshit. There is no evidence to support that. Most mutations have little or no effect. On average humans are thought to have 3 or 4 mutations each. Most of those have little or no effect.

Word to you - your sig is not funny nor are you logical nor are you using evidence.

And my mother is dead but she had a degree in anthropology.

Ethelred

210
1 / 5 (2) May 22, 2011
Well heck, old 'ethey' called to the rescue by his cohort in intellectual crime, here we go then:
"Yes. Death. And repair mechanism."

Apoptosis -programmed cell death, is turned OFF by cancer cells, it does this every time cancer shows its angry face,..the HeLa line of cancer cells are still around though Henrietta Lacks has been dead for over 40 years. No, death is not a very good constraining factor and the snails show NO sign of having need or use of a repair mechanism. Evolution requires a point or two of localized pressure, a response to a stimulus not just random mutation.
It is intuitive, unbridled mutation would make life itself impossible and I don't have to prove that...to intelligent human beings...ooooh!

"Nothing else is needed nor is there any evidence that anything is involved."
There is something else involved since selected changes are deselected, as shown in the links I included WITHOUT eliminating any other traits as random mutation tends to do...
210
1 / 5 (1) May 22, 2011
Further: Random mutation cannot be evolution's blueprint because random mutation being also mostly fatal, mostly, cannot deselect changes it has made, since it is RANDOM...U...do...know...what random...means...right?
Here is a video of a cone snail: http://video.nati...one.html
This deadly creature is deadly poisonous exceeded only by the awesome box jelly fish, BUT, head a few hundred miles from their largest habitat and you find the same family of jelly fish, same, living in fresh water and COMPLETELY LACKING ANY VENOM OR STINGING MECHANISM. The difference? Environmental pressure, the second group sees NONE of the predatory activity the larger group does...same bird-one don't fly: ADAPTATION right before your eyes...yes..even YOUR eyes.
Evolution is adaptation to a living world that is itself changing, not random guessing at what should be fancy at the next party.
WORD-TO-YA-MUTHAS
Ethelred
5 / 5 (1) May 23, 2011
Well heck, old 'ethey' called to the rescue by his cohort in intellectual crime, here we go then:
Oh dear starting right of with a lie. I guess you wouldn't want to sully your reputation by telling the truth.

Apoptosis -programmed cell death, is turned OFF by cancer cells,
And what does have to do with the price of peyote in Peru? Nothing. Death of the ORGANISM is what we are talking about.

Henrietta Lacks has been dead for over 40 years.
Yes. So what. SHE is dead and no longer able to reproduce and the cells only reproduce in labs.

. No, death is not a very good constraining factor
Yeah especially if you lie by bringing in laboratory cancers that have nothing to do with the reproduction of organisms except by killing of the organism thus SELECTING Henrieta OUT of the gene pool. Evolution in action.>>
Ethelred
5 / 5 (2) May 23, 2011
and the snails show NO sign of having need or use of a repair mechanism
Sure they do. They, like EVERY species have DNA repair mechanisms. Those without them died off billions of years ago.

Evolution requires a point or two of localized pressure, a response to a stimulus not just random mutation
I said that. THE ENVIRONMENT does the selecting. That is the pressure and I NEVER claimed selection random. That is a lie you tell.

It is intuitive, unbridled mutation would make life itself impossible
But we don't have that. We have SELECTION and mutation. And you are the only one claiming that the mutation is unbridled.

There is something else involved
No.

since selected changes are deselected,
No. That is a lie. Selection is the REMOVAL of changes so they are gone and cannot be deselected since DEATH is permanent.>>
Ethelred
5 / 5 (2) May 23, 2011
as shown in the links I included WITHOUT eliminating any other traits as random mutation tends to do...
Which is not selection. It is SELECTION BY DEATH due to the ENVIRONMENT that causes evolution. Random mutation can and does remove traits. If those traits are needed to survive then that mutation is SELECTED OUT by death.

Further: Random mutation cannot be evolution's blueprint
I never made any such a claim That is a LIE you tell. Selection is NOT random.

because random mutation being also mostly fatal,
False. Mostly they are neutral.

cannot deselect changes it has made, since it is RANDOM.
You either need to start THINKING or quit lying. Selection IS NOT BY MUTATION. Selection is BY DEATH to the organism not being able to survive in the environment.

.U...do...know...what random...means...right?
Do know what DEATH is? I know what random is and it is NOT selection. You are either totally pigheaded on this or lying.>>
Ethelred
5 / 5 (2) May 23, 2011
Environmental pressure, the second group
BINGO. The ENVIRONMENT does the selection. Which is what I said. And you lied about.

ADAPTATION right before your eyes...yes..even YOUR eyes.
BY DEATH. Which is what I said.

Evolution is adaptation to a living world that is itself changing,
YES. It is due to random mutation followed by selection by the ENVIRONMENT.

not random guessing at what should be fancy at the next party.
That is something you made up. I NEVER SAID ANYTHING REMOTELY LIKE THAT.

So lets go over this again for people, like you, that don't understand.

There is no goal for evolution EXCEPT survival and reproduction. No species knows the future. The environment does not know the future. There is only a process and no goal no thought no planning.>>
Ethelred
5 / 5 (4) May 23, 2011
There are mutations. The mutations are of different types. From single point mutations, that change one codon all the way to a complete new copy of an entire chromosome, or a fusing of two chromosomes. Some mutations are more likely than others. Single point is the most common.

The mutations are NOT selection and I no clue as the where you go that from. I sure didn't claim it. I gather you got it from another Creationist.

Mutations usually are neutral. Some make changes that kill. That results in SELECTION the ORGANISM OUT of the gene pool. Some mutations merely lower the odds of reproduction and over time they will be selected OUT of the gene pool since they will die out. Some mutations are advantageous, rare but it does happen. Those will improve the odds of reproduction. Indeed that IS what makes them advantageous.>>
Ethelred
5 / 5 (4) May 23, 2011
The selection is by the ENVIRONMENT. The environment includes other members of the species thus there can also be sexual selection but that is still by the environment. Selection is by DEATH or failure to reproduce which is the same thing as far as the genome is concerned.

Mutation produces the raw material of evolution. Selection prunes out the changes that lower the chances of survival.

Which boils down to:

Evolution doesn't have a goal. It's not a conscious entity. The mutations that don't kill the animal before it reproduces are passed on. It's as simple as that.
Which is rather sparse but completely accurate.>>
Ethelred
5 / 5 (2) May 23, 2011
Link one of yours
Reverse evolution in real-time
Key part.
Says Henrique, 'In 2001 we showed that evolution is reversible in as far as phenotypes are concerned, but even then, only to a point. Indeed, not all the characteristics evolved back to the ancestral state.
Which is exactly what can be expected by mutations followed by selection. The phenotype reversed SOMETIMES to SOME DEGREE and an exact reversal of the genes did not occur. This supports me completely and you not at all.

Link two
"Reverse Evolution" Discovered in Seattle Fish

We call it 'reverse evolution' because the sticklebacks are reverting to an ancestral phenotype [or appearance], that of the marine sticklebacks, which originally founded the lake populations,
PHENOTYPE not GENOTYPE. Do you understand the difference? In both cases there really isn't a reversal. There is only evolution to adapt to a changed environment. Similar environment will USUALLY produce similar organisms.
>>
Ethelred
5 / 5 (2) May 23, 2011
In the second case a simple mutation can turn off or turn on a single trait, which in this case produces the armour. So a single point mutation can produce the change. It is highly unlikely that the same exact coding is involved here but it is possible since the only change needed could easily be the START codon.

So what you said here is true.
No, something is guiding them,
The ENVIRONMENT is what guides them. It knows nothing of the future and doesn't care one whit what happens. It only effects the odds of reproduction.

Seek the adaptive trigger.
We have found it. Long ago. Darwin and Wallace knew what the trigger was and is. The ENVIRONMENT.

Ethelred
210
1 / 5 (3) May 23, 2011
Okay, 'ethey' you win-done with it..now to the LISTENING public:

Mutation: http://www.readsc...ion.html
My comments R @ Random Mutation bcause controlled or non-random wood B manmade(statistically skewed/unnatural as far as selection of the fit) or extraterrestrial.
HeLa cancer was mentioned because Henrietta Lacks though cancer ridden HAD NINE CHILDREN and died giving birth to number ten: Arguing that she was "selected out" is an obvious error. Cancer occurs in over 200 different types and it IS a mutation -has been around for over 5000 years just counting humanity, dinosaurs even had it and it IS a mutation but not selection (An Asteroid kill).
Random mutation, cannot account for all the varieties of life and form seen in our world nor in the cone snail:Natural DNA recombination meets the definition of a very precise instrument for change as well as normal reproduction. Cancer/death unless it wipes out a species, does not prevent change, nor make it.Fin
aroc91
5 / 5 (2) May 23, 2011
Cancer is a somatic mutation. Although there is predisposition, which is genetic and can be passed on, you can't select against cancer. Cancer has absolutely nothing to do with this article/discussion.
Ethelred
5 / 5 (2) May 24, 2011
Okay, 'ethey' you win-done with it..now to the LISTENING public:
OK I didn't listen. I READ it instead.

My comments R @ Random Mutation
Mutation is random or mostly so. SELECTION is by the environment and not random. You seem to be unable to make the connection and unwilling to stop pretending that there is only mutation in the theory of evolution.

HeLa cancer was mentioned because Henrietta Lacks though cancer ridden HAD NINE CHILDREN and died giving birth to number ten:
So. Then she may have passed on a rather nasty gene. And some genes for having a lot children which is usually advantageous. Evolution is a process. It has no goal except for survival and that only for reproduction. A gene that causes painful death but increases offspring is going to be selected FOR.

Arguing that she was "selected out" is an obvious error.
She didn't have any more children did she? So OK I didn't know she had children. Thus she is irrelevant to your point.>>
Ethelred
5 / 5 (2) May 24, 2011
What it means is the her cancer wasn't disadvantageous. She reproduced and that is all that matters in evolution. No one ever claimed the process gave a damn if it caused pain. Indeed pain EVOLVED because it increased the chances of reproduction.

Cancer occurs in over 200 different types and it IS a mutation -
It isn't a mutation in that is inheritable. Only mutations that are inherited can be part of the evolutionary process.

dinosaurs even had it and it IS a mutation but not selection (An Asteroid kill).
You really don't understand mutation as it pertains to evolution. CANCERS are caused by NEW mutations of somatic cells and not by mutations in the germ cells. The mutations that lead to a propensity to have cancer CAN be passed on but the mutations that sent the SOMATIC cells out of control are NOT passed on and thus cannot contribute to the next generation.

Random mutation, cannot account for all the varieties of life
And I sure never claimed it did.>>
Ethelred
5 / 5 (2) May 24, 2011
Mutation PLUS SELECTION by the ENVIRONMENT does account for evolution and thus the varieties of life.

:Natural DNA recombination meets the definition of a very precise instrument for change as well as normal reproduction.
It isn't precise. Its rather sloppy even after billions of years of evolution. If it wasn't sloppy there wouldn't be cancer or repair mechanisms or errors in copying. Which would lead to extinction by not be able to compete with the species that did evolve by having a sloppier genome.

Cancer/death unless it wipes out a species, does not prevent change, nor make it.Fin
Nor does it have a lot to do with evolution. It has SOMETHING to do with it. But only in cancers that kill before reproduction.

You really should quit beating around the bush. I know what your point is but you refuse to be explicit. YOU are pushing ID which is not needed to explain anything in evolution. Being cutesy has lead to your post being a garbled mess.>>
Ethelred
5 / 5 (2) May 24, 2011
Cancer has no more and no less to do with evolution than any other cause of death that stops an organism from reproducing. I had a suspicion that you had gone off into a fantasy land when you mentioned apoptosis which while it did evolve is NOT the sort of death that is involved in evolution since it does not stop an organism from reproducing. It evolved to IMPROVE the chances of reproduction.

The link you posted supports me completely. Thank you.

You really should read it. Here is the relevant parts. There are two.

(2) Germinal/gametic mutatnt- When gametes are affected by mutation it is called gametic mutation. As a result of this mutaton offsprings are affected. It is expressed in homozygous state when mutation is a recessive one. But in case of dominant mutatnt it will be expresses in every generations, e.g., Haemophilia is a X-linked recessive mutant.
I put that one first because that is part that is relevant to evolution.>>
Ethelred
5 / 5 (2) May 24, 2011
Only germ cell mutations are passed on so only those participate in the inheritable changes that are subject to the process of Natural Selection in the next generation.

(1) Somatic mutation- somatic mutation occurs in the somatic cell to develop a mutatnt tissue among the normal tissues. Phenotype expression is only found when the mutation is dominant one, e.g., delicious apple, Washington oranges, etc. Sometimes somatic mutation can be serious to the individual if the mutation is concerned with malignant growth.
Which is what you have been confusing with the mutations that are involved in Natural Selection.>>
Ethelred
5 / 5 (2) May 24, 2011
My guess is that you ran across mutation in somatic cells in an article about Lacks and then, because you simply don't understand evolution bu do want to push ID, you fixated on the mutations and didn't even think that might have had nothing to do with Natural Selection since she had already reproduced.

I am sorry that I didn't understand where you were trying to go. However that was because you don't understand what you were trying to talk about. It doesn't help that you don't want to be honest about your intent either. If you want to have an honest discussion about ID you shouldn't try to hide that you are talking about ID. In case you have not noticed it I don't do sort of hidden agenda post. I think it is duplicitous at best and just plain dishonest in many cases.

Oh and sneering at me when you don't understand what you trying to talk about is silly.

Ethelred
aroc91
not rated yet May 24, 2011
Well said, Ethelred.