Van Wassenbergh Sam, Day Steven W, Hernández L Patricia, Higham Timothy E, Skorczewski Tyler
Department of Biology, Ghent University, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium; Department of Biology, University of Antwerp, Universiteitsplein 1, B-2610 Antwerpen, Belgium.
Department of Mechanical Engineering, Rochester Institute of Technology, 76 Lomb Memorial Dr., Rochester, NY 14623, USA.
J Theor Biol. 2015 May 7;372:159-67. doi: 10.1016/j.jtbi.2015.03.001. Epub 2015 Mar 10.
To expand the buccal cavity, many suction-feeding fishes rely on a considerable contribution from dorsal rotation of the dorsal part of the head including the brains, eyes, and several bones forming the braincase and skull roof (jointly referred to as the neurocranium). As the neurocranium takes up a large part of the total mass of the head, this rotation may incur a considerable inertial cost. If so, this would suggest a significant selective pressure on the kinematics and mass distribution of the neurocranium of suction feeders. Here, an inverse dynamic model is formulated to calculate the instantaneous power required to rotate the neurocranium, approximated by a quarter ellipsoid volume of homogeneous density, as well as to calculate the instantaneous suction power based on intra-oral pressure and head volume quantifications. We applied this model to largemouth bass (Micropterus salmoides) and found that the power required to rotate the neurocranium accounts for only about 4% of the power required to suck water into the mouth. Furthermore, recovery of kinetic energy from the rotating neurocranium converted into suction work may be possible during the phase of neurocranial deceleration. Thus, we suggest that only a negligible proportion of the power output of the feeding muscles is lost as inertial costs in the largemouth bass. Consequently, the feeding performance of piscivorous suction feeders with generalised morphology, comparable to our model species, is not limited by neurocranial motion during head expansion. This suggests that it is thus not likely to be a factor of importance in the evolution of cranial shape and size.
为了扩大口腔，许多吸食性鱼类很大程度上依赖于头部背侧部分（包括脑、眼睛以及构成脑壳和颅顶的几块骨头，统称为神经颅骨）的背向旋转。由于神经颅骨占头部总质量的很大一部分，这种旋转可能会产生相当大的惯性成本。如果是这样，这将表明对吸食性鱼类神经颅骨的运动学和质量分布存在显著的选择压力。在此，建立了一个逆动力学模型，以计算旋转神经颅骨所需的瞬时功率（将其近似为具有均匀密度的四分之一椭球体体积），以及根据口腔内压力和头部体积量化来计算瞬时吸力功率。我们将此模型应用于大口黑鲈（Micropterus salmoides），发现旋转神经颅骨所需的功率仅占将水吸入口腔所需功率的约4%。此外，在神经颅骨减速阶段，从旋转的神经颅骨回收的动能有可能转化为吸力功。因此，我们认为在大口黑鲈中，作为惯性成本损失的进食肌肉输出功率比例可忽略不计。因此，具有与我们的模型物种相似的一般形态的食鱼吸食性鱼类的进食性能，在头部扩张过程中不受神经颅骨运动的限制。这表明它不太可能是颅骨形状和大小进化中的一个重要因素。
