Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.
Department of Biology, Dickinson College, Carlisle, PA 17013, USA.
J Exp Biol. 2022 Mar 15;225(6). doi: 10.1242/jeb.243119. Epub 2022 Mar 24.
The evolution of constriction and of large prey ingestion within snakes are key innovations that may explain the remarkable diversity, distribution and ecological scope of this clade, relative to other elongate vertebrates. However, these behaviors may have simultaneously hindered lung ventilation such that early snakes may have had to circumvent these mechanical constraints before those behaviors could evolve. Here, we demonstrate that Boa constrictor can modulate which specific segments of ribs are used to ventilate the lung in response to physically hindered body wall motions. We show that the modular actuation of specific segments of ribs likely results from active recruitment or quiescence of derived accessory musculature. We hypothesize that constriction and large prey ingestion were unlikely to have evolved without modular lung ventilation because of their interference with lung ventilation, high metabolic demands and reliance on sustained lung convection. This study provides a new perspective on snake evolution and suggests that modular lung ventilation evolved during or prior to constriction and large prey ingestion, facilitating snakes' remarkable radiation relative to other elongate vertebrates.
蛇类的收缩和大型猎物摄取行为的进化是关键创新，这可能解释了相对于其他长形脊椎动物，该类群具有显著的多样性、分布和生态范围。然而，这些行为可能同时阻碍了肺部通气，使得早期的蛇类在这些行为进化之前必须规避这些机械限制。在这里，我们证明了王蛇可以根据身体壁运动的物理阻碍来调节用于肺部通气的肋骨的特定节段。我们表明，肋骨特定节段的模块化驱动可能是由于衍生辅助肌肉的主动募集或静止。我们假设，如果没有模块化的肺通气，收缩和大型猎物摄取就不太可能进化，因为它们干扰了肺通气、高代谢需求以及对持续肺对流的依赖。本研究为蛇类进化提供了新的视角，并表明，在收缩和大型猎物摄取之前或期间，模块化的肺通气就已经进化，这使得蛇类相对于其他长形脊椎动物具有显著的辐射能力。
