Dean Mason N, Bizzarro Joseph J, Clark Brett, Underwood Charlie J, Johanson Zerina
Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany.
Institute of Marine Sciences, University of California, Santa Cruz, CA 95060, USA.
R Soc Open Sci. 2017 Sep 6;4(9):170674. doi: 10.1098/rsos.170674. eCollection 2017 Sep.
The shapes of vertebrate teeth are often used as hallmarks of diet. Here, however, we demonstrate evidence of frequent piscivory by cartilaginous fishes with pebble-like teeth that are typically associated with durophagy, the eating of hard-shelled prey. High-resolution micro-computed tomography observation of a jaw specimen from one batoid species and visual investigation of those of two additional species reveal large numbers of embedded stingray spines, arguing that stingray predation of a scale rivalling that of the largest carnivorous sharks may not be uncommon for large, predatory batoids with rounded, non-cutting dentition. Our observations demonstrate that tooth morphology is not always a reliable indicator of diet and that stingray spines are not as potent a deterrent to predation as normally believed. In addition, we show that several spines in close contact with the jaw skeleton of a wedgefish () have become encased in a disorganized mineralized tissue with a distinctive ultrastructure, the first natural and unequivocal evidence of a callus-building response in the tessellated cartilage unique to elasmobranch skeletons. Our findings reveal sampling and analysis biases in vertebrate ecology, especially with regard to the role of large, predatory species, while also illustrating that large body size may provide an escape from anatomical constraints on diet (e.g. gape size, specialist dentition). Our observations inform our concepts of skeletal biology and evolution in showing that tessellated cartilage-an ancient alternative to bone-is incapable of foreign tissue resorption or of restoring damaged skeletal tissue to its original state, and attest to the value of museum and skeletal specimens as records of important aspects of animal life history.
脊椎动物牙齿的形状常被用作饮食特征。然而，在这里我们证明了软骨鱼类频繁捕食鱼类的证据，这些软骨鱼类有着卵石状牙齿，通常与食硬壳猎物的食壳性相关。对一种鲼形目物种的颌骨标本进行高分辨率微计算机断层扫描观察，并对另外两个物种的标本进行视觉研究，发现了大量嵌入的黄貂鱼刺，这表明对于具有圆形、无切割功能齿列的大型掠食性鲼形目动物来说，捕食与最大的肉食性鲨鱼相当规模的黄貂鱼可能并不罕见。我们的观察表明，牙齿形态并不总是饮食的可靠指标，而且黄貂鱼刺对捕食的威慑作用并不像通常认为的那么大。此外，我们发现，与尖吻魟（）颌骨骨骼紧密接触的几根刺已经被包裹在一种结构紊乱、具有独特超微结构的矿化组织中，这是板鳃亚纲骨骼特有的棋盘状软骨中形成骨痂反应的首个自然且明确的证据。我们的发现揭示了脊椎动物生态学中的采样和分析偏差，特别是关于大型掠食性物种的作用，同时也表明大体型可能使动物摆脱饮食方面的解剖学限制（如口裂大小、特化齿列）。我们的观察结果有助于我们理解骨骼生物学和进化，表明棋盘状软骨（一种古老的骨骼替代物）无法对外来组织进行吸收，也无法将受损的骨骼组织恢复到原始状态，并证明了博物馆和骨骼标本作为动物生命史重要方面记录的价值。
