Research in News
An Arms Race Among Venomous Animals?
(Hebrew University press release)
In a new study published in the journal PLoS Genetics, scientists at the Hebrew University of Jerusalem have revealed new discoveries about how animal venom evolves.
Venom is a complex mixture of proteins and other toxic chemicals produced by animals such as snakes and spiders, either to incapacitate their prey or to defend against predators. The influence of positive selection (the process by which a protein changes rapidly over evolutionary time scales) in expanding and diversifying animal venoms is widely recognized. This process was hypothesized to result from an evolutionary chemical arms race, in which the invention of potent venom in the predatory animals and the evolution of venom resistance in their prey animals, exert reciprocal selection pressures. In contrast to positive selection, the role of purifying selection (also known as negative selection, which is the selective removal of deleterious genetic changes from a population) has rarely been considered in venom evolution. Moreover, venom research has mostly neglected ancient animal groups in favor of focusing on venomous snakes and cone snails, which are both “young” animal groups that originated only recently in evolutionary timescales, approximately 50 million years ago. Consequently, it was concluded that venom evolution is mostly driven by positive selection.
In the new study, Dr. Yehu Moran at the Hebrew University’s Department of Ecology, Evolution and Behavior and the guest scientist Dr. Kartik Sunagar examined numerous venom genes in different animals in order to unravel the unique evolutionary strategies of toxin gene families. The researchers analyzed and compared the evolutionary patterns of over 3500 toxin sequences that belonged to 85 different families. These toxins spanned the breadth of the animal kingdom, including ancient venomous groups such as centipedes, scorpions, spiders, coleoids (octopus, cuttlefish and squids) and cnidarians (jellyfish, sea anemones and hydras). Unexpectedly, despite their long evolutionary histories, ancient animal groups were found to have accumulated low variation in their toxins.
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