Stinson Charlotte M, Deban Stephen M
Department of Biology, California State University, Bakersfield, Bakersfield, CA 93311, USA
Department of Integrative Biology, University of South Florida, Tampa, FL 33620, USA.
J Exp Biol. 2017 Nov 1;220(Pt 21):3896-3907. doi: 10.1242/jeb.164285.
Salamanders use the hyobranchial apparatus and its associated musculature for tongue projection on land and for suction feeding in water. Hyobranchial apparatus composition and morphology vary across species, and different morphologies are better suited for feeding in aquatic versus terrestrial environments. We hypothesize that differences in hyobranchial morphology result in functional trade-offs in feeding performance. We predict that semi-aquatic and aquatic salamandrids with hyobranchial morphology suited for aquatic feeding will have lower performance, in terms of tongue-projection distance, velocity, acceleration and power, compared with terrestrial salamandrids when feeding in a terrestrial environment. We found that semi-aquatic and aquatic newts had lower velocity, acceleration and muscle-mass-specific power of tongue projection when compared with the terrestrial salamanders and The fully aquatic newt, , has a robust, heavily mineralized hyobranchial apparatus and was unable to project its tongue during terrestrial feeding, and instead exhibited suction-feeding movements better suited for aquatic feeding. Conversely, terrestrial species have slender, cartilaginous hyobranchial apparatus and enlarged tongue pads that coincided with greater tongue-projection distance, velocity, acceleration and power. exhibited extreme tongue-projection performance, similar to that seen in elastically projecting plethodontid salamanders; muscle-mass-specific power of tongue projection exceeded 2200 W kg, more than 350 times that of the next highest performer, , which reached 6.3 W kg These findings reveal that two fully terrestrial salamandrids have morphological specializations that yield greater tongue-projection performance compared with species that naturally feed in both aquatic and terrestrial environments.
蝾螈利用舌骨装置及其相关肌肉组织在陆地上伸出舌头，并在水中进行吸食式进食。舌骨装置的组成和形态因物种而异，不同的形态更适合在水生环境与陆地环境中进食。我们假设舌骨形态的差异会导致进食性能方面的功能权衡。我们预测，与陆地蝾螈相比，具有适合水生进食的舌骨形态的半水生和水生蝾螈科动物在陆地环境中进食时，在舌头伸出距离、速度、加速度和功率方面的表现会更低。我们发现，与陆地蝾螈相比，半水生和水生蝾螈伸出舌头的速度、加速度和肌肉质量比功率更低。完全水生的蝾螈拥有坚固、高度矿化的舌骨装置，在陆地进食时无法伸出舌头，而是表现出更适合水生进食的吸食式进食动作。相反，陆生物种具有细长的软骨舌骨装置和扩大的舌垫，这与更大的舌头伸出距离、速度、加速度和功率相吻合。表现出极端的舌头伸出性能，类似于在具有弹性伸出舌头的无肺螈科蝾螈中看到的；舌头伸出的肌肉质量比功率超过2200W/kg，是下一个表现最佳者（达到6.3W/kg）的350倍以上。这些发现表明，与自然在水生和陆地环境中进食的物种相比，两种完全陆生的蝾螈具有形态学上的特化，从而产生更大的舌头伸出性能。
