Correlations between form, function and behaviour: the inner ears of birds and reptiles

脊椎动物的内耳是一个复杂的结构，包括平衡器官和听力器官。这两种感觉对生物体的正常功能都是必不可少的：不出所料，人们从软解剖和生理/神经机制方面对现存脊椎动物的内耳进行了深入的研究，并对耳朵功能的行为和一般生物学意义进行了深入的研究。软组织被安置在骨性结构中，这些骨性结构构成了头骨后部脑壳侧壁的一部分。很少有研究试图寻找骨骼结构的属性(例如体积、最大长度/宽度、形状)、听力或平衡感与动物由此产生的行为指标之间的相关性。从古生物学家的角度来看，这是一个不幸的遗漏，因为在大多数情况下，化石只提供关于有机体坚硬解剖的信息。部分由于这种情况，到目前为止，许多灭绝的脊椎动物的内耳几乎没有受到关注，直到最近随着非破坏性成像技术的出现，详细的研究才成为可能。我们提出了一项概念验证研究，以调查内耳形态在评估已灭绝的爬行动物和鸟类的行为和听觉表现方面的作用。我们将测试爬行动物/鸟类内耳解剖的差异是否可以用行为、发声、声音功能和社会组织的差异来解释。这项测试将基于对40种现存爬行动物和鸟类的内耳解剖结构的分析，这些内耳解剖结构将被选为代表广泛的声音和听觉行为。关于内耳解剖的数据将使用X射线计算机断层扫描(CT)来收集，这将使我们能够建立耳朵骨骼结构的详细3D虚拟模型。我们将寻求拉格纳的大小(内耳容纳听力器官/基底乳头的部分)、动物已知的听觉能力(例如，可检测到的声音频率范围、灵敏度)和动物表现出的行为范围(例如，使用发声交流的行为与不使用发声交流的行为)之间的相关性。这些不同的数据来源(内耳骨骼解剖、耳朵功能和动物行为)的组合是一种新的方法，将为推断灭绝动物的行为提供严格的基础。如果耳朵解剖、听力和行为之间没有相关性，这将使我们可以证伪已灭绝的爬行动物和鸟类的听力功能的现有假说。然而，如果确定了相关性，该项目将作为未来对各种已灭绝物种(例如，包括非鸟类恐龙和早期羊膜动物)的听力和行为调查的先导研究。此外，该项目还将提供大量关于现存爬行动物和鸟类内耳的新解剖学信息，这对听觉生物学家、动物学家和系统学家都有重要价值。

The vertebrate inner ear is a complex structure that incorporates the organs of balance and hearing. Both senses are essential to the normal functioning of an organism: unsurprisingly, the inner ears of living vertebrates have been studied intensively in terms of their soft anatomy and their physiological/neurological mechanisms, and the behavioural and general biological implications of ear function have been investigated thoroughly. The soft tissues are housed in bony structures that form part of the side walls of the braincase at the back of the skull. Few studies have attempted to seek correlations between the properties of the bony structures (e.g. volume, maximum length/width, shape), hearing ability or sense of balance, and the resulting behavioural repertoire of an animal. From a palaeontologist's perspective, this is an unfortunate omission as, in most cases, fossils only yield information on the hard anatomy of an organism. Partly as a result of this situation, the inner ears of many extinct vertebrates have received little attention hitherto and detailed studies have only become possible recently with the advent of non-destructive imaging technology. We propose a proof-of-concept study to investigate the utility of inner ear morphology in assessing the behaviour and auditory performance of extinct reptiles and birds. We will test whether differences in reptile/bird inner ear anatomy can be explained by differences in behaviour, vocalisation, acoustic function and social organisation. This test will be based upon an analysis of the inner ear anatomy of 40 living reptiles and birds, which will be chosen to represent a wide range of vocal and auditory behaviours. Data on inner ear anatomy will be collected using X-ray Computerised Tomography (CT), which will allow us to build detailed 3-D virtual models of the ear's bony structures. Correlations will be sought between the dimensions of the lagena (that part of the inner ear housing the organ of hearing / the basilar papilla), the known auditory abilities of an animal (e.g. range of sound frequencies detectable, sensitivity), and the range of behaviours that the animal exhibits (e.g. those that use vocal communication versus those that do not). Combination of these different data sources (inner ear bony anatomy, ear function and animal behaviour) is a novel approach and will provide a rigorous basis for inferring behaviour in extinct animals. If no correlations exist between ear anatomy, hearing ability and behaviour this will allow us to falsify existing hypotheses of hearing function in extinct reptiles and birds. However, if correlations are identified this project will act as a pilot study for future investigations on hearing and behaviour in a variety of extinct species (including non-avian dinosaurs and early amniotes, for example). In addition, the project will provide a large amount of new anatomical information on the inner ears of living reptiles and birds, which will be of great value to auditory biologists, zoologists and systematists.