Dial Terry R, Lauder George V
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA.
J Morphol. 2020 Aug;281(8):956-969. doi: 10.1002/jmor.21224. Epub 2020 Jun 17.
What is the functional effect of prolonged development? By controlling for size, we quantify first-feeding performance and hydrodynamics of zebrafish and guppy offspring (5 ± 0.5 mm in length), which differ fivefold in developmental time and twofold in ontogenetic state. By manipulating water viscosity, we control the hydrodynamic regime, measured as Reynolds number. We predicted that if feeding performance were strictly the result of hydrodynamics, and not development, feeding performance would scale with Reynolds number. We find that guppy offspring successfully feed at much greater distances to prey (1.0 vs. 0.2 mm) and with higher capture success (90 vs. 20%) compared with zebrafish larvae, and that feeding performance was not a result of Reynolds number alone. Flow visualization shows that zebrafish larvae produce a bow wave ~0.2 mm in length, and that the flow field produced during suction does not extend beyond this bow wave. Due to well-developed oral jaw protrusion, the similar-sized suction field generated by guppy offspring extends beyond the horizon of their bow wave, leading to successful prey capture from greater distances. These findings suggest that prolonged development and increased ontogenetic state provides first-feeding fish time to escape the pervasive hydrodynamic constraints (bow wave) of being small.
长期发育的功能效应是什么？通过控制大小，我们量化了斑马鱼和孔雀鱼幼体（体长5±0.5毫米）的初次摄食性能和流体动力学，它们在发育时间上相差五倍，在个体发育状态上相差两倍。通过操纵水的粘度，我们控制了以雷诺数衡量的流体动力学状态。我们预测，如果摄食性能严格是流体动力学的结果，而不是发育的结果，那么摄食性能将随雷诺数而变化。我们发现，与斑马鱼幼体相比，孔雀鱼幼体能够在距离猎物大得多的地方成功摄食（分别为1.0毫米和0.2毫米），且捕获成功率更高（分别为90%和20%），而且摄食性能并非仅由雷诺数决定。水流可视化显示，斑马鱼幼体产生一个长度约为0.2毫米的弓形波，并且在吸食过程中产生的流场不会延伸到这个弓形波之外。由于发育良好的口腔颌部突出，大小相似的孔雀鱼幼体产生的吸食场延伸到了它们弓形波的范围之外，从而能够从更远的距离成功捕获猎物。这些发现表明，延长的发育和增加的个体发育状态为初次摄食的鱼类提供了时间，使其能够摆脱因体型小而普遍存在的流体动力学限制（弓形波）。
