Technology that can map out the genes at work in a snake or lizard's mouth has, in many cases, changed the way scientists define an animal as venomous. If oral glands show expression of some of the 20 gene families associated with "venom toxins," that species gets the venomous label. But, a new study from The University of Texas at Arlington challenges that practice, while also developing a new model for how snake venoms came to be. The work, which is being published in the journal Molecular Biology and Evolution, is based on a painstaking analysis comparing groups of related genes or "gene families" in tissue from different parts of the Burmese python, or Python molurus bivittatus.

A team led by assistant professor of biology Todd Castoe and including researchers from Colorado and the United Kingdom found similar levels of these so-called toxic gene families in python oral glands and in tissue from the python brain, liver, stomach and several other organs. Scientists say those findings demonstrate much about the functions of venom genes before they evolved into venoms. It also shows that just the expression of genes related to venom toxins in oral glands of snakes and lizards isn't enough information to close the book on whether something is venomous.

"Research on venom is widespread because of its obvious importance to treating and understanding snakebite, as well as the potential of venoms to be used as drugs, but, up until now, everything was focused in the venom gland, where venom is produced before it is injected," Castoe said. "There was no examination of what's happening in other parts of the snake's body. This is the first study to have used the genome to look at the rest of that picture."