Evolution in colubrids

[Simon R. Sansom]

Dr. Fry,

I've heard that Atractaspis venom is fairly potent. In addition to the relatively potent venom, why have they developed such huge venom glands? Why does a fossorial snake need that huge quantity of venom?

Cheers!

Simon

[Dr. Bryan Fry]

Hi Simon

Yeah, the Atractaspis genus (Stilleto snakes) are weird little bast*rds. Why they have the side opening fangs may be from the burrowing (they don't even need to open their mouths to pop the fangs out).

They don't actually put out that much venom relatively speaking, the long gland is quite thin. and doesn't secrete really that much more. It is quite potent though and contains a unique toxin class called sarafotoxins. These guys have a devastating effect upon the blood pressure, jacking it up very very quickly and violently.

They also have a couple big enzymes, the M12B class of metalloproteinases, this class is one of the 'ancestral toxins' that were in the venom of the very first venomous snake.

The Atractaspids are therefore a good example of how venom has evolved, it still has as one of its major venom components one of the original toxins but it also has a unique toxin type (sarafotoxins) that is found only in these venoms.

Cheers
B