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Jason_Hood
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Random Question

Post by Jason_Hood »

Me and a buddy were talking and he said something that got me thinking. He said way more colubrids lay eggs than give live birth. I thought hmmm is that accurate?? So does anybody know anywhere to find an accurate number for egg layers versus live born colubrids??

Jason
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Kevin Messenger
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Re: Random Question

Post by Kevin Messenger »

I would agree, though I don't think I would use the words "way more" as opposed to just "more." But, unfortunately I don't know of a place that has any numbers. For the US - you could simply take the Crother book and go through and make a tally of live vs egg, but world wide... I don't have a clue of where to turn to. If I were to break it down into percentages, I would wager maybe 65% eggs and 35% live birth
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Sam Sweet
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Re: Random Question

Post by Sam Sweet »

The answer will depend on how you define "colubrids" -- with or without natricines, homalopsines, etc.
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FunkyRes
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Re: Random Question

Post by FunkyRes »

This might be what Sam is talking about, but I think the Colubrid snake family use to be kind of a dumping ground and since then, several snake species previously lumped into it have been moved out of colubrid, IE I believe Garters are now no longer classified as colubrids.
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Kevin Messenger
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Re: Random Question

Post by Kevin Messenger »

^ if that is the case then that changes everything. I knew lots of subfamilies were out there, and I was kind of thinking the same, i.e., depends on your classification of Colubridae. For example, I knew Natracinae existed (what garters belong to), but I didn't think it was elevated to family status yet. Has it been?
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Brian Folt
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Re: Random Question

Post by Brian Folt »

Kevin,

Vitt and Caldwell's most recent textbook has not elevated the subfamilies to family status. I'm assuming this is based off the most recent research/opinions?. That being said, my herpetology professor (Scott Moody) had us learn the subfamilies as families (i.e. in Ohio, Colubridae, Natricidae, Diapsidae, and Xenodontidae), as he personally felt that was more appropriate. It seems sensible to me...

It was nice meeting you at the conference a few months ago. Your recent post was great - I wish the Kirtland's I've seen were as gorgeous as yours....

Brian
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Sam Sweet
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Re: Random Question

Post by Sam Sweet »

Molecular phylogenetics based on nuclear genes (rather than mtDNA, which tends to hit its saturation limit around the age of divergence of major clades of advanced snakes) has been tending to support family status for the deeper divisions of "Colubridae". And yes, it's been a garbage can for a long time. A number of the apparently important genera are rare animals, and thus not often available to the usual lab-coat types, so progress is slow and concordance among studies is still rather low.

To your original question, something less than a quarter of species of colubrids in the general sense are live-bearers, mostly the natricines, with a scattering of species (usually fully aquatic) in other subfamilies. Harry Greene reckons that livebearing has evolved independently around 35 times among all snakes.
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-EJ
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Re: Random Question

Post by -EJ »

Again... I could be wrong but I seem to remember hearing in a lecture that live bearing snakes are not truely viviperous.
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Kevin Messenger
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Re: Random Question

Post by Kevin Messenger »

They aren't, that is why I prefer the term ovoviviparous. No, it is not "true viviparity" - I think that term would only be reserved for mammals, in the truest sense of the word.

In this thread, when they say live-bearing they basically are meaning "non-oviparous"
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Jason_Hood
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Re: Random Question

Post by Jason_Hood »

Thanks for all the replies guys. I did mean old school "colubrid" as we were just having a general discussion about "cottonmouth eggs" and what snake could possibly be confused with a cottonmouth near the water and lay eggs. Then we rolled over to the topic of how many snake actually lay eggs.

So no real science was harmed in this discussion. :lol:

Jason
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gbin
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Re: Random Question

Post by gbin »

-EJ wrote:Again... I could be wrong but I seem to remember hearing in a lecture that live bearing snakes are not truely viviperous.
Kevin Messenger wrote:They aren't, that is why I prefer the term ovoviviparous. No, it is not "true viviparity" - I think that term would only be reserved for mammals, in the truest sense of the word.

In this thread, when they say live-bearing they basically are meaning "non-oviparous"
Actually, a number of reproductive biologists dislike the archaic term "ovoviviparous" and won't use it, preferring to stick with "viviparous" (or using some other term that relates more specifically to what they're talking about at the time). The problem is that internally there is (of course ;) ) a multi-layered continuum rather than a clear distinction between what ultimately results in viviparity (live-bearing) and oviparity (egg-laying), with various ways to split things up depending upon exactly what type of maternal-embryonic communication one is talking about, and various evolutionary imperatives underlying them. So "ovoviviparity" is considered by these scientists to be at best muddling instead of clarifying, and at worst misleading.

For one treatment of this subject in the scientific literature, interested readers might like to look up:

D.G. Blackburn. 2000. Classification of the reproductive patterns of amniotes. Herpetological Monographs 14:371-377.

Sorry to drag the thread further off your intended topic, Jason, but I felt obliged to respond. :)

Gerry
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