Quoll

The pro's here probably have caught up with this news, but for the rest of us I thought this was interesting.

Venom systems in reptiles are thought to have evolved only once. Contrast this with something like light detection (eyes) - aren't they estimated to have arisen multiple times?

Anyway, the good news is we can all still keep our pet goannas!http://www.smh.com.au/news/science/v...016892739.html

Quoll

Hey Oolon, is this another for your sub-optimal design list? The goanna produces venom, but its less effective than in snakes because of its delivery method (ie via saliva getting into a puncture (rip) made by the teeth, rather than directly into the wound via fangs.

I'd have thought snakes and lizards are similar enough that the designer could have cut and paste fangs into the lizard design.

Berthold

I looked up if goanna was another name for Gila Monster (as far as I know, the only venomous lizard), but it isn't.

Also, I had supposed that snakes are a clade. But this now looks as if [venomous lizards + venomous snakes] are a clade. Is that compatible with all that is known about other traits of these suborders?

The Lone Ranger

I don't think so. As far as I know, snakes are a legitimate clade. I suppose it may be that possession of venom in snakes is a "primitive" trait and lack of venom is a derived trait.

In fact many more snakes are venomous than most people would suspect. An awful lot of "nonvenomous" snakes simply have venom that isn't strong-enough to be dangerous to humans or (as in most rear-fanged snakes, for instance) aren't normally capable of envenoming a human. For example, garter snakes (genus Thamnophis) are almost universally considered to be non-venomous, but, in fact, they are venomous. It's simply that their venom isn't normally dangerous to humans. A few unusually sensitive individuals have become quite ill after being bitten by garter snakes, however.


Of course, the line between "venom" and "saliva with strong digestive enzymes" is a rather fuzzy one.

Cheers,

Michael

Berthold

Thank you very much!

I had thought that the term "venom system" does not mean the enzymatic wherewithal but the means of application. As for that, the vipers and crotalids are latecomers in the cenozoic (extremely rare or totally absent in the eocene), so I had not considered that non-venomousness might be a secondary trait.

Coragyps

The Cuban mammal Solenodon has been mentioned here not that long ago: they have venemous saliva and a grooved tooth - a not quite a hollow fang - to help deliver it. Well, and they're so unattractive that they ugly their prey to death.

espritch

I wonder how it took so long for anyone to notice that Goannas have venom glands. Surely someone has disected one before?