Fang evolution in venomous snakes: Adaptation of 3D tooth shape to the biomechanical properties of their prey

Abstract

Venomous snakes are among the world's most specialized predators. During feeding, they use fangs to penetrate the body tissues of their prey, but the success of this penetration depends on the shape of these highly specialized teeth. Here, we examined the evolution of fang shape in a wide range of snakes using 3D geometric morphometrics (3DGM) and cross‐sectional tooth sharpness measurements. We investigated the relationship of these variables with six diet categories based on the prey's biomechanical properties, and tested for evolutionary convergence using two methods. Our results show that slender elongate fangs with sharp tips are used by snakes that target soft‐skinned prey (e.g., mammals), whereas fangs become more robust and blunter as the target's skin becomes scaly (e.g., fish and reptiles) and eventually hard‐shelled (e.g., crustaceans), both with and without correction for evolutionary allometry. Convergence in fang shape is present, indicating that fangs of snakes with the same diet are more similar than those of closely related species with different diets. Establishing the relationship between fang morphology and diet helps to explain how snakes became adapted to different lifestyles, while also providing a proxy to infer diet in lesser known species or extinct snakes from the fossil record.

Bioinspired Robust Mechanical Properties for Advanced Materials

“…Studies have assessed the sharpness index to understand the correlation between the fang angle and the puncture. [67,68] The sharpness of fangs differs based on their eating habits. For example, a soil burrower has blunt fangs while prey-eating Viperidae reptiles have sharp fangs (Figure 6K).…”

“…Copyright 2020, Elsevier Ltd. L) Comparison of fangs depending on diet and variation of sharpness index. Reproduced with permission [68]. Copyright 2021, John Wiley & Sons, Inc.…”

Evolutionary allometry and ecological correlates of fang length evolution in vipers

“…The fangs of vipers are highly specialized dental structures, injecting venom from a duct that passes through the maxilla and empties into the top of the hollow fang. Despite the function of puncture and injection of venom seemingly being simple, fangs vary extensively in shape and length [10,11,27,44]. Our work quantitatively assessed several potential correlates of fang length evolution to provide insights into the adaptive significance of this key functional trait linking predator to prey.…”

“…Finally, longer fangs may assist in making contact with more evasive mammalian prey (e.g. [49]), as occurs with the evolution a jaw mobility in some fishes [50,51] The evolution of fang length based on taxonomic diet composition may therefore stem from a complex suite of these putative selective forces, of which none are mutually exclusive [11].…”

“…There may be equally strong selection on morphological variation in the venom injection apparatus among taxa [8,9]. If prey differ in size, shape or handling requirement, alternative evolutionary optima may exist for the venom injection system, providing a route to diversification [10][11][12].…”