Posted on 02/21/2006 6:39:30 AM PST by GreenFreeper
EARLY EVOLUTION OF THE VENOM SYSTEM IN LIZARDS AND SNAKES 2006 Nature 439: 584-588
Bryan G. Fry, Nicolas Vidal, Janette A. Norman, Freek J. Vonk, Holger Scheib, S. F. Ryan Ramjan, Sanjaya Kuruppu, Kim Fung, S. Blair Hedges, Michael K. Richardson, Wayne. C. Hodgson, Vera Ignjatovic, Robyn Summerhayes, & Elazar Kochva
Abstract: Among extant reptiles only two lineages are known to have evolved venom delivery systems, the advanced snakes and helodermatid lizards (Gila Monster and Beaded Lizard) 1. Evolution of the venom system is thought to underlie the impressive radiation of the advanced snakes (2,500 of 3,000 snake species) 2–5. In contrast, the lizard venom system is thought to be restricted to just two species and to have evolved independently from the snake venom system1. Here we report the presence of venom toxins in two additional lizard lineages (Monitor Lizards and Iguania) and show that all lineages possessing toxin-secreting oral glands form a clade, demonstrating a single early origin of the venom system in lizards and snakes. Construction of gland complementary-DNA libraries and phylogenetic analysis of transcripts revealed that nine toxin types are shared between lizards and snakes. Toxinological analyses of venom components from the Lace Monitor Varanus varius showed potent effects on blood pressure and clotting ability, bioactivities associated with a rapid loss of consciousness and extensive bleeding in prey. The iguanian lizard Pogona barbata retains characteristics of the ancestral venom system, namely serial, lobular non-compound venom-secreting glands on both the upper and lower jaws, whereas the advanced snakes and anguimorph lizards (including Monitor Lizards, Gila Monster and Beaded Lizard) have more derived venom systems characterized by the loss of the mandibular (lower) or maxillary (upper) glands. Demonstration that the snakes, iguanians and anguimorphs form a single clade provides overwhelming support for a single, early origin of the venom system in lizards and snakes. These results provide new insights into the evolution of the venom system in squamate reptiles and open new avenues for biomedical research and drug design using hitherto unexplored venom proteins.
First evidence of a venom delivery
A pdf of this article can be accessed and downloaded at the CNAH pdf library. Go to:
http://www.cnah.org/cnah_pdf.asp
SNAKE FANGS FROM THE LOWER MIOCENE OF GERMANY: EVOLUTIONARY STABILITY OF PERFECT WEAPONS
FReepmail me to be added or removed to the ECO-PING list!
If this is some lead in to refer to James "Serpent Head" Carville...cool.
It that is what they want to believe so be it.
We went straight from snakes to politicians in the first post!
Actually snakes are an enjoyable animal to have around, whereas a politician, well, I think we can all agree that there is quite possibly not a lower life form.
So, this solves global warming. Cool.
..and a real insult to reptiles worldwide.
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