Snakes and lizards share venom, evolutionary history, scientists say

<body leftmargin="0" bgcolor="#000060" text="#FFFFFF" link="#FFFF00" vlink="#FF9900"> <table border="0" cellpadding="0" cellspacing="0" width="95%" height="1"> <tr> <center> <td valign="top" width="33%" height="33"> <b> <p class="MsoNormal"><font face="Arial" size="5">Snakes and lizards share venom, evolutionary history, study finds</font></p> </b> <p class="MsoNormal"><font face="Arial" size="1">Nov. 16, 2005<br> Courtesy Nature<br> and World Science staff<br> <br> </font><b><font size="2" face="Arial">Conventional wisdom has it that, among reptiles, venom delivery is something mainly associated with snakes, and underlies their dramatic evolutionary success: 2,500 out of 3,000 snake species are poisonous. <br> <br> In contrast, venom delivery is found in just two lizard species, in which it is thought to have evolved independently from snakes. <br> <br> </p> </font> <font size="2" face="Arial"> But a new study by Bryan Fry of the University of Melbourne, Australia, and colleagues, to be published online by the research journal <i>Nature</i> this week, has found that that venom delivery among lizards is in fact much more widespread. <br> <br> The researchers said they showed that at least some members of two additional major lizard lineages also produce and can deliver venom toxins.</font> <p><font size="2" face="Arial">The two additional lineages are called varanids, which include Monitor Lizards; and iguanians, which include iguanas. <br> <br> The new work suggests that the side-effects of nasty lizard bites may actually be due to venom rather than incidental bacterial infection, as was previously thought, according to Fry and colleagues.<br> <br> Also, they said, the findings suggest snakes and lizards are much more closely related than has been previously thought. Snakes evolved from relatively advanced lizards, they said, rather than being a separate branch on the evolutionary tree.<br> <br> Among living reptile species, only the Gila Monster and Beaded Lizard were previously known to be poisonous, the researchers wrote. They claimed to have found toxins in four Varanid species and the Eastern Bearded Dragon, an iguanian.<br> <br> A new genetic analysis shows that all lineages with toxin-secreting glands share a common ancestor, they claimed.<br> <br> This demonstrates “a single early origin of the venom system in lizards and snakes,” probably about 200 million years ago, they said, during the dinosaur era.<br> <br> The research opens new avenues for drug development based on still unknown molecules found in lizard venom, they added.<br> <br> “These molecules represent a tremendous hitherto unexplored resource not only for understanding reptile evolution but also for use in drug design and development,” they wrote.</font></b> <font size="2" face="Arial"> <b> </p> <p>* * *</p> </b> <p><b><font face="Arial" size="2" color="#FFFFFF">Send us a <a href="mailto:editor@world-science.net">comment</a> on this story, or <a href="mailto:?Body=http://www.world-science.net/othernews/051116_venomfrm.htm">send it to a friend</a></font></b> </p> <p> </center> </font> </td> </tr> </table> </body>