Dept. of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
Dept. of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.
J Exp Biol. 2018 Jun 5;221(Pt 11):jeb178160. doi: 10.1242/jeb.178160.
Suction-feeding fish rapidly expand the mouth cavity to generate high-velocity fluid flows that accelerate food into the mouth. Such fast and forceful suction expansion poses a challenge, as muscle power is limited by muscle mass and the muscles in fish heads are relatively small. The largemouth bass powers expansion with its large body muscles, with negligible power produced by the head muscles (including the sternohyoideus). However, bluegill sunfish - with powerful strikes but different morphology and feeding behavior - may use a different balance of cranial and axial musculature to power feeding and different power outputs from these muscles. We estimated the power required for suction expansion in sunfish from measurements of intraoral pressure and rate of volume change, and measured muscle length and velocity. Unlike largemouth bass, the sternohyoideus did shorten to generate power, but it and other head muscles were too small to contribute more than 5-10% of peak expansion power in sunfish. We found no evidence of catapult-style power amplification. Instead, sunfish powered suction feeding by generating high power outputs (up to 438 W kg) from their axial muscles. These muscles shortened across the cranial half of the body as in bass, but at faster speeds that may be nearer the optimum for power production. Sunfish were able to generate strikes of the same absolute power as bass, but with 30-40% of the axial muscle mass. Thus, species may use the body and head muscles differently to meet the requirements of suction feeding, depending on their morphology and behavior.
摄食性鱼类会迅速扩张口腔，产生高速的流体流动，从而加速食物进入口中。这种快速而有力的抽吸扩张带来了挑战，因为肌肉力量受到肌肉质量的限制，而鱼头中的肌肉相对较小。大口黑鲈利用其庞大的身体肌肉来实现扩张，头部肌肉（包括胸骨舌骨肌）产生的力量可以忽略不计。然而，蓝鳃太阳鱼——虽然具有强大的攻击能力，但形态和摄食行为不同——可能会利用头部和轴肌的不同平衡来为摄食提供动力，并从这些肌肉中产生不同的功率输出。我们通过测量口腔内的压力和容积变化率来估算太阳鱼在抽吸扩张过程中所需的功率，并测量了肌肉长度和速度。与大口黑鲈不同的是，胸骨舌骨肌确实会缩短以产生力量，但它和其他头部肌肉太小，无法为太阳鱼的扩张功率贡献超过 5-10%的峰值。我们没有发现弹射式功率放大的证据。相反，太阳鱼通过其轴肌产生高功率输出（高达 438 W/kg）来为抽吸摄食提供动力。这些肌肉在头部到身体的一半处缩短，就像在大口黑鲈中一样，但速度更快，可能更接近功率产生的最佳状态。太阳鱼能够产生与大口黑鲈相同的绝对力量的攻击，但只需其轴肌质量的 30-40%。因此，不同物种可能会根据自身的形态和行为，以不同的方式利用身体和头部肌肉来满足抽吸摄食的要求。
