Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th St., Chicago, IL 60637, USA.
Department of Ecology, Evolution, and Organismal Biology, Brown University, 80 Waterman St., Providence RI 02912, USA.
Biol Open. 2022 Sep 15;11(9). doi: 10.1242/bio.059447. Epub 2022 Sep 12.
Suction feeding in fishes is characterized by rapid cranial movements, but extant lungfishes (Sarcopterygii: Dipnoi) exhibit a reduced number and mobility of cranial bones relative to actinopterygian fishes. Despite fusion of cranial elements, lungfishes are proficient at suction feeding, though the impacts of novel cranial morphology and reduced cranial kinesis on feeding remain poorly understood. We used X-ray reconstruction of moving morphology (XROMM) to study the kinematics of seven mobile elements (neurocranium, upper jaw, lower jaw, tongue, ceratohyal, clavicle, and cranial rib) and two muscles (costoclavicular portion of the hypaxialis and rectus cervicis) during the feeding strikes of West African lungfish (Protopterus annectens). We found that feeding by P. annectens on non-evasive prey is relatively slow, with a mean time to peak gape of 273 ms. Lower jaw depression and clavicular rotation were hinge-like, with one degree of freedom, but the ceratohyals rotated in a complex motion involving depression and long-axis rotation. We quantified the relative contributions to oral cavity volume change (RCVC) and found that oral cavity expansion is created primarily by ceratohyal and clavicle motion. P. annectens suction feeds relatively slowly but successfully through muscle shortening of hypaxial and rectus cervicis muscles contributing to hyoid mobility.
鱼类的抽吸式进食以快速的头部运动为特征，但现存的肺鱼（肉鳍鱼纲：总鳍鱼目）相对于硬骨鱼具有较少数量和运动能力的头骨骨骼。尽管头骨元素融合，肺鱼仍然能够很好地进行抽吸式进食，但新颖的头骨形态和减少的头骨运动对进食的影响仍知之甚少。我们使用运动形态的 X 射线重建（XROMM）来研究七种可移动元素（颅腔、上颌、下颌、舌、齿状骨、锁骨和头肋骨）和两块肌肉（胸肋肌的锁骨部分和颈直肌）在西非肺鱼（非洲肺鱼）进食时的运动学。我们发现，肺鱼捕食非逃避性猎物的速度相对较慢，最大张口时间的平均值为 273 毫秒。下颌骨的下凹和锁骨的旋转呈铰链状，具有一个自由度，但齿状骨的旋转运动涉及到下凹和长轴旋转的复杂运动。我们量化了对口腔容积变化（RCVC）的相对贡献，发现口腔的扩张主要是由齿状骨和锁骨的运动产生的。肺鱼的抽吸式进食速度相对较慢，但通过胸肋肌和颈直肌的肌肉缩短，成功地实现了舌骨的运动。
