Reptile & Amphibian Forums

Our data support the monophyly of the elapids (CP = 99%) and include Atractaspis in this clade. This taxon has been classified as a viperid (Underwood 1967), a colubrid (Hardaway and Williams 1976; Smith et al. 1977; Dowling and Duellman 1978) or an independent lineage allied with the elapids (McDowell 1986, 1987; Dessauer et al. 1987; Cadle 1988).--Heise et al. (1995)

Reference:
Philip J. Heise, Linda R. Maxson, Herndon G. Dowling, and S. Blair Hedges (1995). Higher-level snake phylogeny inferred from mitochondrial DNA sequences of 12S rRNA and 16S rRNA genes. Mol. Biol. Evol. 12: 259–265.

Gee so you can read ???

Are we supposed to applaud or something ???

How about you either say what you have to say, or disappear ???

Have a great day

David

>>Our data support the monophyly of the elapids (CP = 99%) and include Atractaspis in this clade. This taxon has been classified as a viperid (Underwood 1967), a colubrid (Hardaway and Williams 1976; Smith et al. 1977; Dowling and Duellman 1978) or an independent lineage allied with the elapids (McDowell 1986, 1987; Dessauer et al. 1987; Cadle 1988).--Heise et al. (1995)
>>
>>Reference:
>>Philip J. Heise, Linda R. Maxson, Herndon G. Dowling, and S. Blair Hedges (1995). Higher-level snake phylogeny inferred from mitochondrial DNA sequences of 12S rRNA and 16S rRNA genes. Mol. Biol. Evol. 12: 259–265.
>>
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David Williams
PNG Snake Venom Research Project
PO Box 168
Port Moresby, NCD, PNG.

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Heise et al.'s findings contrast sharply with Fry et al.'s "best guess" tree. Heise et al. find Atractaspis to be the sister taxon of Bungarus, an elapid. Fry et al. has Atractaspis as the sister taxon to Leioheterodon madagascariensis, and these two are in turn sister taxa to Psammophis mossambicus.

The discrepancy in these two hypotheses is large and irreconcilable. Either one or both must be wrong. Personally I think Fry et al.'s tree is wrong.

>>Heise et al.'s findings contrast sharply with Fry et al.'s "best guess" tree. Heise et al. find Atractaspis to be the sister taxon of Bungarus, an elapid. Fry et al. has Atractaspis as the sister taxon to Leioheterodon madagascariensis, and these two are in turn sister taxa to Psammophis mossambicus.
>>
>>The discrepancy in these two hypotheses is large and irreconcilable. Either one or both must be wrong. Personally I think Fry et al.'s tree is wrong.
>>
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WW Home

I have presented evidence to contradict your "best guess" tree. What do you have to say, WW? Ignore the evidence? Looks like you guessed incorrectly. Better guess again.

If facts contradict theory, then one can either ignore the theory or ignore the facts. I, for one, choose to ignore Fry et al.'s "best guess" tree instead of ignoring the contradictory evidence.

You obviously have a fondness for anonymous ranting through infinite internet forum threads.

However, this arena has reached its inherent limiation. I'd like to suggest we move this somewhere more appropriate. Since you are so sure in your beliefs, why don't you write a letter to the editor of Toxicon (the most appropriate journal in this case) stating your case. We'll respond and then the world can take it from there.

Shall we dance?
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Dr. Bryan Grieg Fry
Deputy Director
Australian Venom Research Unit
University of Melbourne

www.venomdoc.com

As I said in my last post, I have shown evidence that contradicts Fry et al.'s "best guess" tree. If you have something that could refute that evidence, show the world now. Why delay?

Or are you too afraid?

Your tree is contradicted by Heise et al. (1995). Your hypothesis is based partly on your tree and mostly on chemical similarities. Since chemical similarity has been shown to be unreliable evidence of homology, and since your tree has been contradicted by mtDNA data, your hypothesis is pretty much falsified as far as I am concerned. Ignoring contradictory evidence will not save your theory. Refuting it will. Therefore it is best for you to refute the evidence I present instead of ignoring it. But can you do it?

There you go, backing down again. The story of your life.

You can talk the talk but its pretty obvious that you cannot walk the walk. Put it to paper and I'll be more than happy to respond in detail. However, I suspect that you are loath to do this since it would require you to drop your clock of anonymity, putting your name next to your 'facts', which you will have to arrange into some sort of logical thread.
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Dr. Bryan Grieg Fry
Deputy Director
Australian Venom Research Unit
University of Melbourne

www.venomdoc.com

Once again, you avoided answering the question of how you are going to refute Heise et al.'s finding that Atractaspis is an elapid, which contradicts your "best guess" tree. It may be because you are not a taxonomist, unlike your collaborator WW. Your collaborator claims that Heise et al.'s neighbor-joining method is "unsophisticated." That may be so, but their placement of Atractaspis within the Elapidae is corroborated by most systematists who worked with this taxon. It is also corroborated by tooth morphology, since Atractaspis has the hollow fangs that are characteristic of elpaids. Sophisticated or not, it is contradictory data. You can run but you cannot hide from contradictory data.

Yeah turn it up mate. I really don't care about Atractaspis other than the fact that the M12B peptidases in the venom formed a monophyletic clade with elapid and viper venoms, with the toxins all mixed together. Thus, this toxin class was evolved prior to the split by the vipers and is part of the evidence for the single origin of venom. That is all.

So, yes or no. Are you going to write a letter to the editor to Toxicon laying out your evidence for the case of multiple, independent evolution of snake venoms? Yes or no?
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Dr. Bryan Grieg Fry
Deputy Director
Australian Venom Research Unit
University of Melbourne

www.venomdoc.com

If similarities in chemical structure is irrefutable proof of homology, then tetrodotoxin must have evolved in the common ancestor of the puffer fishes and the blue ringed octupus and it has subsequently been lost in other kinds of fishes and in other kinds of octopuses. Clearly this is not the case since tetrodotoxin is of bacterial origin. Since an estimated 60-70% of colubrids, according to Dr. Kenneth Kardong, lack the Duvernoy's gland and they therefore lack toxins, the venom evolved first in the colubroid ancestor hypothesis is just as untenable as the monophyletic origin of tetrodotoxin.

Write a letter to the editor with supporting evidence or just go away. I really don't care either way ::yawn::

I know, and it is quite obvious, that some people "do not care" about opposing evidence. For those who do care about the evidence, it is well known that chemical similarities (opsin, crystallin and Pax-6) between the eyes of different animals such as the octopus and the fish are the result of convergent evolution because their eyes are structurally and developmentally different, suggesting independent origin. Further Fry et al.'s definition of venom has been rebuffed by Kenneth Kardong, who shows that according to their definition, human saliva is venom, since they define venom as toxic secretions. Kardong writes:

'The point is as obvious as this: human saliva is toxic[67] with clinical manifestations if injected subcutaneously.[68] But from this pharmacological property (toxic) or from these clinical symptoms (erythema, edema) we would not conclude that humans use their saliva as a venom! Toxicity is clearly an incidental byproduct of human saliva, not an indication of biological role. The biological role is determined by how the secretion contributes to an animal’s survival, which can be determined only by actual empirical study of its use in the wild.[69] Outside of the few colubrids that can rapidly kill prey and defend with oral secretions, the biological role(s) of Duvernoy’s secretion are today unknown and unverified.[70]'

Therefore, the unsupported claim that Duvernoy's glands are "venom glands" and that the secretions are "venom" are based on phramacological definitions, not biological ones. There is no shortage of published data which refute the claim of Fry et al. but these are obviously ignored nevertheless.

Reference
Kenneth V. Kardong 2002. Colubrid Snakes and Duvernoy’s "Venom" Glands J. TOXICOL.—TOXIN REVIEWS, 21(1&2), 1–19