Data from: Specialized specialists and the narrow niche fallacy: a tale of scale-feeding fishes

Although rare within the context of 30,000 species of extant fishes, scale-feeding as an ecological strategy has evolved repeatedly across the teleost tree of life. Scale-feeding (lepidophagous) fishes are diverse in terms of their ecology, behavior, and specialized morphologies for grazing on scales and mucus of sympatric species. Despite this diversity, the underlying ontogenetic changes in functional and biomechanical properties of associated feeding morphologies in lepidophagous fishes are less understood. We examined the ontogeny of feeding mechanics in two evolutionary lineages of scale-feeding fishes: Roeboides, a characin, and Catoprion, a piranha. We compare these two scale-feeding taxa to their nearest, non-lepidophagous taxa to identify traits held in common among scale-feeding fishes. We use a combination of micro-computed tomography scanning and iodine staining to measure biomechanical predictors of feeding behavior such as tooth shape, jaw lever mechanics, and jaw musculature. We recover a stark contrast between the feeding morphology of scale-feeding and non-scale-feeding taxa, with lepidophagous fishes displaying some paedomorphic characters through to adulthood. Few traits are shared between lepidophagous characins and piranhas, except for their highly-modified, stout dentition. Given such variability in development, morphology, and behavior, ecological diversity within lepidophagous fishes has been underestimated.尽管在现存的3万余种鱼类中，食鳞行为（scale-feeding）作为一种生态策略仍属罕见，但该策略已在真骨鱼类生命之树（teleost tree of life）中多次独立演化。食鳞鱼类（lepidophagous fishes）在生态学、行为学以及用于刮食同域分布物种（sympatric species）鳞片与黏液的特化形态方面均表现出丰富的多样性。尽管存在此类多样性，但学界对食鳞鱼类相关摄食形态结构的功能与生物力学（biomechanical）特性背后的个体发育（ontogenetic）变化仍知之甚少。本研究针对两类食鳞鱼类演化支系开展了摄食力学的个体发育研究：其一为脂鲤科鱼类（characin）罗碧脂鲤属（Roeboides），其二为水虎鱼（piranha）卡特普里翁属（Catoprion）。我们将这两类食鳞类群与其最近的非食鳞近亲类群进行对比，以识别食鳞鱼类共有的性状特征。本研究结合显微计算机断层扫描（micro-computed tomography）与碘染色（iodine staining）技术，对摄食行为的生物力学预测指标进行量化，包括牙齿形态、颌骨杠杆力学以及颌部肌肉特征。研究结果显示，食鳞与非食鳞类群的摄食形态结构存在显著差异：食鳞鱼类在成年后仍保留部分幼态持续（paedomorphic）性状。除高度特化且粗壮的齿列（dentition）外，食鳞脂鲤与食鳞水虎鱼之间共有的性状极少。鉴于食鳞鱼类在发育、形态与行为上的高度变异性，其生态多样性此前被学界低估。