Fangs for the Memories? A Survey of Pain in Snakebite Patients Does Not Support a Strong Role for Defense in the Evolution of Snake Venom Composition

Abstract

Animals use venoms for multiple purposes, most prominently for prey acquisition and self-defense. In snakes, venom composition often evolves as a result of selection for optimization for local diet. However, whether selection for a defensive function has also played a role in driving the evolution of venom composition has remained largely unstudied. Here, we use an online survey of snakebite victims to test a key prediction of a defensive function, that envenoming should result in the rapid onset of severe pain. From the analysis of 584 snakebite reports, involving 192 species of venomous snake, we find that the vast majority of bites do not result in severe early pain. Phylogenetic comparative analysis shows that where early pain after a bite evolves, it is often lost rapidly. Our results, therefore, do not support the hypothesis that natural selection for antipredator defense played an important role in the origin of venom or front-fanged delivery systems in general, although there may be intriguing exceptions to this rule.

Mutual enlightenment: A toolbox of concepts and methods for integrating evolutionary and clinical toxinology via snake venomics and the contextual stance

“…One such lineage is caenophidian snakes, which explosive radiation in the wake of the Cretaceous–Paleogene mass extinction approximately 60–50 million years ago ( Hsiang et al, 2015 ), was perhaps a consequence of the evolution of venom ( Fry et al, 2006 , 2012 ). Snake venom is thought to have evolved primarily as a trophic adaptation, that is for predatory purposes ( Davies and Arbuckle, 2019 ; Ward-Smith et al, 2020 ), and among the ca. 3700 extant snakes, at least 800 species (within Elapidae, Viperidae, Colubridae and Atractaspididae) use venom to immobilize their invertebrate or vertebrate prey before swallowing it whole.…”

Convergent Evolution of Pain-Inducing Defensive Venom Components in Spitting Cobras

“…Snake venoms consist of variable mixtures of proteinaceous components that cause potent hemotoxic, neurotoxic and/or cytotoxic pathologies in both prey and potential adversaries, including humans ( 2 ). Previous evidence suggests that venom variation is largely driven by dietary variation ( 3 ), but defensive drivers of snake venom evolution are rarely considered (although see ( 4 )). The evolution of venom projection or ‘spitting’ in cobras offers an excellent model system for exploring the evolution of defensive toxins, as this behavior has no role in prey capture, targets specific sensory tissues, and is the only long-distance, injurious defensive adaptation among almost four thousand species of snakes.…”

Duvernoy’s Gland Transcriptomics of the Plains Black-Headed Snake, Tantilla nigriceps (Squamata, Colubridae): Unearthing the Venom of Small Rear-Fanged Snakes

“…Venom has independently evolved over 100 times across the Tree of Life, amounting to more than 200,000 species which use this protein and peptide mixture for prey capture and predator defense [ 1 , 2 , 3 , 4 ]. Snakes have evolved several different venom delivery systems primarily for prey capture [ 5 , 6 ]. Solenoglyphous and proteroglyphous (“front-fanged”) taxa—those with moveable or fixed hollow front fangs that deliver venom from a pressurized venom gland, such as vipers and elapids—have been focal systems in venom research, providing invaluable insight into ecology and natural history [ 7 , 8 , 9 , 10 , 11 ], evolution and phylogenetic patterns [ 12 , 13 , 14 , 15 ], behavior and physiology [ 16 , 17 , 18 ], and importantly the global snakebite epidemic [ 19 , 20 ].…”