Snake venom research has historically been predominantly focused on front-fanged species belonging to the Viperidae and Elapidae families. This focus has limited our understanding of the evolution of venom in rear-fanged snakes throughout their ecologically diverse lineage. One particular component of venom, known as three-finger toxins (3FTxs), exhibits neurotoxic properties and is present in the venoms of certain rear-fanged snakes, specifically within the Colubrinae subfamily of the Colubridae family.
However, there remains uncertainty about the extent of 3FTx prevalence both in terms of its expression within venom glands and its distribution among various species within the Colubrinae subfamily. In a recent study by Srodawa et al. (2023), a transcriptomic approach was employed to characterize the venom expression patterns of four distinct colubrine snake species native to the Neotropics. These species, identified as Chironius, Oxybelis, Rhinobothryum, and Spilotes, exhibited a predominant expression of 3FTxs.
By conducting gene tree reconstructions of 3FTxs, the researchers uncovered intriguing evidence of potentially novel heterodimers within the genetic sequences of Chironius multiventris and Oxybelis aeneus. This discovery points to a remarkable instance of parallel evolution, indicating that structural changes in 3FTxs have independently occurred among rear-fanged colubrine snakes. Additionally, the study identified positive selection in specific sites located within the structural loops or “fingers” of 3FTxs. These regions are likely crucial binding sites that facilitate interactions with molecules from prey.
The findings underscore the significance of delving into the venom profiles of less-studied species. Such investigations play a pivotal role in piecing together the complete evolutionary narrative of toxins across the entire spectrum of life’s evolutionary tree.
Srodawa K, Cerda PA, Davis Rabosky AR, Crowe-Riddell JM. 2023. Evolution of Three-Finger Toxin Genes in Neotropical Colubrine Snakes (Colubridae). Toxins 15(9):523.
