Weller H I, Olsen A M, Camp A L, Manafzadeh A R, Hernandez L P, Brainerd E L
Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA.
Department of Musculoskeletal Biology, University of Liverpool, Liverpool, UK.
Integr Org Biol. 2020 Jun 19;2(1):obaa018. doi: 10.1093/iob/obaa018. eCollection 2020.
Most predatory ray-finned fishes swallow their food whole, which can pose a significant challenge, given that prey items can be half as large as the predators themselves. How do fish transport captured food from the mouth to the stomach? Prior work indicates that, in general, fish use the pharyngeal jaws to manipulate food into the esophagus, where peristalsis is thought to take over. We used X-Ray Reconstruction of Moving Morphology to track prey transport in channel catfish (). By reconstructing the 3D motions of both the food and the catfish, we were able to track how the catfish move food through the head and into the stomach. Food enters the oral cavity at high velocities as a continuation of suction and stops in the approximate location of the branchial basket before moving in a much slower, more complex path toward the esophagus. This slow phase coincides with little motion in the head and no substantial mouth opening or hyoid depression. Once the prey is in the esophagus, however, its transport is surprisingly tightly correlated with gulping motions (hyoid depression, girdle retraction, hypaxial shortening, and mouth opening) of the head. Although the transport mechanism itself remains unknown, to our knowledge, this is the first description of synchrony between cranial expansion and esophageal transport in a fish. Our results provide direct evidence of prey transport within the esophagus and suggest that peristalsis may not be the sole mechanism of esophageal transport in catfish.
大多数掠食性硬骨鱼会将食物整个吞下，考虑到猎物的大小可能是捕食者自身的一半，这可能构成重大挑战。鱼类如何将捕获的食物从口腔运输到胃部？先前的研究表明，一般来说，鱼类会利用咽颌将食物送入食道，据认为蠕动在食道中发挥作用。我们使用运动形态的X射线重建技术来追踪沟鲶体内猎物的运输过程。通过重建食物和鲶鱼的三维运动，我们能够追踪鲶鱼如何将食物通过头部运输到胃部。食物以高速进入口腔，作为吸力的延续，在鳃篮的大致位置停止，然后以慢得多、更复杂的路径向食道移动。这个缓慢阶段与头部几乎没有运动以及没有明显的张口或舌骨凹陷同时发生。然而，一旦猎物进入食道，其运输与头部的吞咽动作（舌骨凹陷、腰带收缩、轴下缩短和张口）惊人地紧密相关。尽管运输机制本身仍然未知，但据我们所知，这是首次描述鱼类颅骨扩张与食道运输之间的同步性。我们的结果提供了食道内猎物运输的直接证据，并表明蠕动可能不是鲶鱼食道运输的唯一机制。
