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

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."

[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