Eyes

[Garter_Gertie]

Anybody know about eyes?

Like garters, nonven-o-mous (that's hard to say!), have round pupils. Many venomous snakes have vertical pupils.

While looking at the Nature Photography thread I saw RepitleParadise's croc picture. They have vertical pupils and are nonvenomous.

Why is there a difference, besides "just because that's the way it its"? Does it have to do, maybe, with further evolving - though I'd be hard pressed to guess which was more evolved - venomous or non.

Are crocs more closely related to rattlers than rattlers are to garters? That can't be as a snake is closer to another snake than a crocodile.

So. Anybody know anything about the difference in pupils?

[Stefan-A]

There's no connection between venom an pupil shapes.

To illustrate my point: garters are venomous and just look at any elapid.

[Garter_Gertie]

Stefan, why do you say garters are venomous and what's an elapid?

[Stefan-A]

Because garters do produce a venom (albeit a very mild one) and elapids (Elapidae) are a family of snakes, which contains such members as cobras, mambas, taipans, kraits and many others, all of which have round pupils and they produce some of the most potent venoms.

So, in short, it's pretty much just because of how things have turned out.

Often vertical pupils are a sign of a nocturnal lifestyle, but not always. If you have a look at boas and pythons (nonvenomous), you'll notice that they often have vertical pupils as well.

[Garter_Gertie]

I'm not 100% positive on this, but I don't think garters are considered venomous over here. I know Hoggys are, because of the way you described garters. But I don't think I've read anything published in the US that considers garters that way.

I'll have to do more research.

Then WHY the eyes? I want to know. Luck of the draw? Crocs aren't nocturnal - yes, I realize you said not always.

This is going to drive me nutz. I'm really curious about this.

[Stefan-A]

I'm pretty sure crocs are especially nocturnal.

Wiley InterScience :: Session Cookies (http://www3.interscience.wiley.com/journal/109919767/abstract?CRETRY=1&SRETRY=0)


Ultrastructure of duvernoy's gland from the wandering garter snake, Thamnophis elegans vagrans (Serpentes, Colubridae)
Kenneth V. Kardong, Daniel L. LuchtelDepartment of Zoology, Washington State University, Pullman, Washington 98164, and Department of Environmental Health, SC-34, University of Washington, Seattle, Washington 98195

Abstract

In addition to the supralabial glands (strips of glandular tissue lying along the maxilla), most snakes of the family Colubridae possess an enlarged oral gland lying behind the eye and emptying near the rear maxillary teeth, the Duvernoy's gland. Duvernoy's gland is most probably homologous to the venom gland of viperid and elapid snakes, and occasionally has been implicated in cases of human envenomation. I just grabbed the first article I could find, there are better ones. Look for ones by a 'Dr. Bryan Fry'. He has written a lot on venoms of "nonvenomous" snakes. And venoms in general.

[Garter_Gertie]

Look for ones by a 'Dr. Bryan Fry'. He has written a lot on venoms of "nonvenomous" snakes. And venoms in general.

Now if THAT'S not an oxymoron, venoms of nonvenomous snakes, I don't know what is!

Thanks, Stefan. And he's from Wash State U! I'll keep looking for stuff. I appreciate you pointing me in the correct direction.

I'll have to look up crocs, too. Maybe I thought that because alligators are diurnal - right (she questions herself, but all she can think of is seeing pics of them during the day...)?

Have I got this correct? It's the saliva of Hoggys and then of garters (as the above suggests [well, actually states without using the word "saliva"]) because Hoggys and garters don't have teeth with channels and rattle snakes do? Hoggies and garters topical vs. injected. Right?

Looks like Dave may be changing his program to include garters with Hoggies in that even though they're not venomous they're venomous.

And I'm going to have to get him to quit using "posinous." :D

[Stefan-A]

I wouldn't say it's saliva and hognoses should, IIRC, have grooved teeth that actually allows it to inject into the prey. Garters have to chew.

[Garter_Gertie]

What I've been taught, the teeth in back rotate forward to puncture and deflate the toad and the paralizing toxin is in the saliva of the Hognose.

[Steven@HumboldtHerps]

I would concur that crocs, pythons, boas, and vipers all regularly lead a nocturnal lifestyle. Most all live in climates, that during summer, get hot enough for an ectotherm (cold-blooded) animal to prefer activity during the cooler temperatures of night. This is especially true for tropical and desert areas. In the case of viperids found further north, the cat eyes might just be a carried-on trait from when an ancestor lived in a hotter clime.

My San Diego Night Snake (non-lethal, but venomous rear-fanged colubrid) is completely nocturnal and has cat eyes!

Regarding venom, Dr. Fry's research also reveals that all snakes have the evolutionary predisposition for producing venom. This means that all snakes could potentially produce venom, but those who don't simply don't have the gene "turned on". Since snakes evolved from lizards, the study also shows that the same gene is present in varanids (monitors), iguanids, bearded dragons (and their relatives), and gila monsters. It is not found in geckos and skinks...

There was a big "WOW!" from me when I read that!

Steve

[Garter_Gertie]

Yeah, Steven! WOW! Fascinating. I like the first paragraph as it explains "Why?" to me. So, like if we could live a million years and watch the cat-eyed snakes like up in MN, MAYBE evolution would change their eyes to round. Do alligators have cat-eyes? I'll have to check since they're found in warm zones.

Are there any warm-zoned snakes that *don't* have cat eyes? If so would they then be active during the heat of the day? But red bellies are active at nite (I think I read that here; I'm positive I did) and they have round pupils.

It's all very confusing to me. But fun and interesting and I'm sure I'll get it once I get education on boas, pythons, genus, species, locales, etc. It's just a matter of learning. Keep the info coming! This eye-thing is ssssoooo fun to learn about.

Gertie, the wannbe herpatologist

[Garter_Gertie]

P.S. So, regarding the 'turned-on-gene,' garter's don't have it turned on, Hoggies kind'a do, and vipers REALLY do. That correct?

I thought lizards evolved from snakes! That snakes wanted to get somewhere, didn't have leges and develope them. So, lizards got lazy and lost their legs?

And lizards and geckos just don't have the gene whatsoever?

[anji1971]

This is interesting stuff!
Good topic, Gertie............I'm learning a fair bit, too!

As for all the evolution, I like to think that one day when I pass on, God will be able to "show" me how everything happened, so I can finally say "Aaaahhhh.............now it all makes sense!"
If only we could go back in time...........

[Garter_Gertie]

Thanks, Anj. I so get into stuff I don't know. I've never evolved mentally from the age of two, "Why?"

There has to be a reason - to me - why things are the way they are because of survival of the fitest. I guess, for rite now until I am able to learn more, I'm just going to have to go with eye-nocturnal thingy. But I just know there's exceptions to that 'rule' and I want to know "Why?" for those expcetions!

My mother always said, "Gertie, I'm SO GLAD you were NOT twins!"

[infernalis]

If only we could go back in time...........

Where would one even begin Anj? how far back? you have entered a dimension of time and space........

[Stefan-A]

P.S. So, regarding the 'turned-on-gene,' garter's don't have it turned on,
Apparently they do have a venom production gene turned ON, considering that..


Secretion from Thamnophis had an LD50 of 33.3 micrograms/gm; Lethal factors and enzymes in the secretion from D...[J Exp Zool. 1985] - PubMed Result (http://www.ncbi.nlm.nih.gov/pubmed/2982993)

[gregmonsta]

Vertical pupils are more suited to night-time hunting are they not? ... hence the variety.

[Garter_Gertie]

I went and read the whole thing, Stefan. Like I understood any of it. Not.

Then WHY am I messing around with venomous snakes????!!! Because they're not for humans? I don't mind adding to Dave's presentation with *additional* info, but I'm not real keen on letting him know it's incorrect to say garters are nonvenomous.

I'm so confused! I won't give up or shut my eyes, but I am frustrated.

Are all, snakes, bascially "venomous" in that there's some enzyme in their saliva (if they've no channeld teeth and cannot be milked) that's an irritant in varying degrees to varying creatures?

(Gertie, running screaming into the nite) -------------------------------------->

[Stefan-A]

It's not a part of their saliva, even if it does mix with saliva because they don't inject their venom.

Well, anyway, I use the term 'harmless' to avoid the issue of whether or not they're venomous.

[aSnakeLovinBabe]

I would not start saying in presentations "these are garter snakes and they are venomous"

people will end up killing every garter snake they see.

[Garter_Gertie]

It's not a part of their saliva, even if it does mix with saliva because they don't inject their venom.

Well, anyway, I use the term 'harmless' to avoid the issue of whether or not they're venomous.

Okay. They have their usual spit PLUS the 'venom' out of that Dubois or whatever gland. And then the TWO mix. Is that correct?

"Harmless." I shall mention that to Dave. He may have to change the entire first part of his presentation. Not that Naturalists can't err and he's not a Herpie for sure. And he is only human... But I'd rather us give correct info than not. I'd sure HATE one of our visitors to find THIS place and come screaming back to us we gave them false or incorrect info.

Sheesh!

[ssssnakeluvr]

What I've been taught, the teeth in back rotate forward to puncture and deflate the toad and the paralizing toxin is in the saliva of the Hognose.
rotate forward??? never heard of that...only moving teeth I have heard of are the pit vipers fangs, they lay flat on the roof of the mouth and are pulled out when the mouth opens...

[ssssnakeluvr]

I thought lizards evolved from snakes! That snakes wanted to get somewhere, didn't have leges and develope them. So, lizards got lazy and lost their legs?



not all did....boas and pythons have spurs and small bones inside at the base of the spurs. I read they are vestigial hip bones. there are fossils of boas and pythons, but I read somewhere that there are fossil colubrids. I don't believe they would be evolved from lizards.

[drache]

I thought lizards evolved from snakes! That snakes wanted to get somewhere, didn't have leges and develope them. So, lizards got lazy and lost their legs?
I know this is a bit off topic
but legs don't necessarily make for better locomotion
in fact, when my plated lizards want to go faster, they tuck their legs flat to their sides and slither

[Stefan-A]

Indeed. Especially in tight places legs will just get in the way.

About the whole venom thing, venom probably predates constriction as a method of subduing prey.

[Garter_Gertie]

Don, yup. Hoggies are rear 'fanged.' I'm assuming it's much the same was as the viper, as hognose teeth lay flat and rotate forward to puncture the toad and deflate it. I'm also assuming as the hognose swallows the toad this pushes the teech back into place.

[Stefan-A]

Don, yup. Hoggies are rear 'fanged.' I'm assuming it's much the same was as the viper, as hognose teeth lay flat and rotate forward to puncture the toad and deflate it. I'm also assuming as the hognose swallows the toad this pushes the teech back into place.
Nope, only the fangs on vipers swing forward (a couple of exceptions exist). The hognoses' "fangs" are fixed.

[drache]

also - I believe that the hognose does need to hold on for a bit, because the teeth are only grooved and merely bring the venom to the site, rather than injecting it

[Steven@HumboldtHerps]

About the whole venom thing, venom probably predates constriction as a method of subduing prey.

I am not so sure about that. I was under the impression that colubrids and vipers are the "newer" snakes and that the intricate varieties of venom (whether lethal or not) are the "cutting edge" of snake evolution.

Fossil record indicate boids to be among the oldest snakes (with their vestigial hips and spurs). I would think (don't quote me on that) death by constriction may go way back!

Steve

[Zephyr]

I actually discussed this with a person who was studying easter indigos at the international science fair; garter snakes, along with most other colubrids, ARE venomous. Their venom (Garter's) is designed to target the nerves of INVERTEBRATE prey. It only has a minor effect on toads. Hence the fact that when you see a garter grab onto a big night crawler, the area becomes puffy and inflamed.

[Stefan-A]

I am not so sure about that. I was under the impression that colubrids and vipers are the "newer" snakes and that the intricate varieties of venom (whether lethal or not) are the "cutting edge" of snake evolution.

Fossil record indicate boids to be among the oldest snakes (with their vestigial hips and spurs). I would think (don't quote me on that) death by constriction may go way back!

SteveThe evolution of the snake from lizards, which also have the gene as you mentioned (meaning that venom actually predates snakes) to a more subterranean lifestyle would suggest that constriction probably wasn't the first method and it certainly wouldn't be a practical one under those conditions. Venom on the other hand would be. Constriction probably wouldn't have been a solution until the snakes started to return to the surface.

But you are definitely right about boids coming early and viperids etc. being a more recent "invention".

[Zephyr]

I also recall there being venom glands in monitors, hinting and ancestor to snakes...

[Steven@HumboldtHerps]

Snake evolution: This conundrum has been locked in debate for many years.
The current argument that snakes evolved from lizards still holds the most ground. But which lizards?

For a while some theorists actually believed that the extinct line of aquatic reptiles known as the mososaurs were the predecessors to the serpentine form. While it sounds good, and mososaurs like the plesiosaur did have elongated serpentine forms, the whole "snakes crawling out of the sea" thing just didn't cut the cake. One might think that sea snakes might have been the orginal snakes, but DNA tells us they are relatively new arrivals on the evolutionary scene. It also does not explain the process of why suspected "live-bearers" such as mososaurs would revert to the egg-laying process that so many snakes today endure.

Going backwards down the snake family tree all the way to primitive boas, sunbeam snakes, and the likes, we may find ourselves looking at something more like skinks, varanids, or anguids. Here we find long, lanky bodies and tails (many), the presence of forked tongues in some families, the evidence of limb reduction (skinks and anguids). Anguids include the legless lizards and the glass lizards (all limbless). We should also not forget that mysterious group of squamates (Remember: the order Squamata includes both snakes and lizards and...): the amphisbaenians! Look these funky sand swimmers up, and you may totally start imagining how things way back when underwent numerous trial and error "experiments". Ha! Another reminder: You don't lose your legs because you need to... Evolution doesn't work that way. You lose your legs because you're a mutant compared to the norm, and the mutation did not affect you ability to survive, and you passed the trait on.... Even if the new trait helps you perhaps survive better than your normal homies, evolution is still an accidental occurrence!

One could surmise that skinks be left out of the list of suspects, simply because they lack the venom genes we have been talking about, and that they are along a separate (older?) lineage of lizards.

Really, look at some pics of some amphisbaenians. Some have front stubs (limbs), and some have hind stubs!

Here is the way I like to paint the picture (and it sure didn't happen overnight; probably took a long time....). Let say you belong to a group of lizards who somehow adapted to a more fossorial (underground) lifestyle. With each subsequent generation you have very subtle mutations whereby you, as a species, slowly change physiology. If you start chasing rodents, worms, or other subterranean prey, legs will get in the way. The serpentine or worm shape is just perfect for an underground lifestyle. With each evolutionary "mistake for the better" you are becoming ruler of the underground niche. Are there any other potential mutations that, in the long run, can serve you better for this lifestyle? Of course there are! You don't need external ear openings. Since you have become elongated, why do you need two lungs side by side? Gosh darn! San keeps getting in under your eyelids; don't need them either; an eye scale works better! And then there are the eyes.... It is very likely that retinal regression occurred in these lizard-snakes - Who needs eyes if you are in complete darkness, and you have a tongue that smells better than most animals?! In regards to the eyes, I believe that the blueprint for a functional eye may have gone dormant and then re-invented itself.

So how do you explain going from above-ground seeing serpentine lizard to fossorial blind lizard-snake to once again above-ground seeing snake? (Remember, their are primitive blind snakes alive today!)

Think apocalypse! We have had numerous extinction level events in Earth's amazing history (too many years for most humans to imagine - We are so small in our scope of time!). Many of these disasters (meteors, comets, super-volcanoes, mega methane burps, glaciation, global warming, etc.) may have left alive only species who were adapted to a more fossorial lifestyle. Say the earth went dark for a while; say the earth's surface was severely pummeled; maybe the underground denizens were better off. Who's to say that when the environment changed (or "got better") some of the burrowers didn't poke their heads out of some holes to smell the sunshine?!

Uh, oh... I have to get off the computer...

Talk to you all soon...

Steve

[Steven@HumboldtHerps]

The evolution of the snake from lizards, which also have the gene as you mentioned (meaning that venom actually predates snakes) to a more subterranean lifestyle would suggest that constriction probably wasn't the first method and it certainly wouldn't be a practical one under those conditions. Venom on the other hand would be. Constriction probably wouldn't have been a solution until the snakes started to return to the surface.

But you are definitely right about boids coming early and viperids etc. being a more recent "invention".

I stand corrected. Thanks Stefan. Makes complete sense.

[adamanteus]

Of course Heloderma have venom glands. I think the recognised ancestors of snakes were early 'skink-like' lizards, which adapted to a subterrainian lifestyle. I have no idea which came first... venom or constriction.... I've never really thought about it... but I will now.

[Stefan-A]

I stand corrected. Thanks Stefan. Makes complete sense.
I may yet stand corrected myself, but at the moment, it seems to me that early snakes wouldn't have been much better at constriction than their lizard ancestors, which may or may not have had the ability to produce venoms.

[Zephyr]

I'm going to say venom came first. :P

[adamanteus]

Maybe not relevent.... but what springs to my mind is certain snakes (such as Pituophis) which are known constrict their prey underground (in burrows) by pressing the animal against the side of it's tunnel. Obviously Pituophis are pretty successful constrictors above ground too.:rolleyes:

[Stefan-A]

I'm going to say venom came first. :P
You better not. :D Say that venom may have come first. ;)

[Zephyr]

Well, we'll never really know for sure until Back to the Future becomes a reality. :P

[Stefan-A]

Maybe not relevent.... but what springs to my mind is certain snakes (such as Pituophis) which are known constrict their prey underground (in burrows) by pressing the animal against the side of it's tunnel. Obviously Pituophis are pretty successful constrictors above ground too.:rolleyes:
Which of the North American snakes was it that would often killed rodents through the sheer force of the strike? Could be a myth, but some species or genus has a reputation for doing that. Pituophis? Coluber?

[adamanteus]

I bet Pituophis could do this. They're also well known for multiple kills, constricting two or more animals at one time.

[Stefan-A]

Well, we'll never really know for sure until Back to the Future becomes a reality. :P
Well, the fact that nobody has come back from the future, pretty much shows that it's not going to become reality. ;)

[Zephyr]

My friend had a garter *this was a LONG time ago* that would take full grown mice. It would absolutely devastate them. My friend would drop a mouse in the cage and it would already be dead. lol

[Garter_Gertie]

Ripley, a bull snake, while a constrictor will sometimes smoosh his prey against the sides of the glass. And he goes down little animal holes.

[Steven@HumboldtHerps]

Perhaps the potential for producing venom was always there, lying dormant, and it didn't start becoming lethal until much later; which would give constriction being first a chance... Perhaps we will never know; we weren't there...

Time machines??? Naaah... Too messy with keeping the continuum intact and all... Perhaps parallel universes... Either way, we'd probably catch a nasty virus from the foreign environment and die in a flaming fever with boils, never having given the origins of snake venom even a second thought! LOL!

Steve