PHYLOGENY AND ONTOGENY OF AN AUDITORY SYSTEM

这项研究试图发现在无耳动物和有耳(听力)动物之间的进化转变过程中，感觉外周和中枢神经系统发生了什么变化。听觉的机械感受性外周和中枢神经系统底物是什么？是否有专门针对听觉和声学行为的新的处理电路出现？或者，来自新的感觉系统的传入信号是否与现有的回路相连？昆虫系统为研究这些问题提供了一个极好的模型，因为在脊椎动物和无脊椎动物中，听觉感受器和耳朵的基本结构非常相似。此外，昆虫的听力已经进化了很多次(大于14次，而脊椎动物不到3次)，所以有许多平行的案例可以比较和对比，以寻找新听觉系统进化的基本规则。螳螂是该项目的焦点动物，它的独特之处在于，它在身体的腹中线拥有一只对超声波敏感的耳朵。以前的研究已经确定了与螳螂最接近的姐妹群蟑螂(没有鼓膜听力)的听觉系统组件的同源物，并详细描述了螳螂耳朵的若虫发育。目前的项目将定义从非听觉行为(蟑螂；听力发育前的螳螂若虫)到听觉行为(成年螳螂)的转变，这些行为必须伴随着听力的获得。这将伴随着对听觉内皮细胞及其同系物的生理学的检查，作为理解行为变化背后的中枢神经系统回路变化的第一步。该项目将研究个体发育路径的进化，这些路径导致螳螂之间不同的听觉能力。它将集中在听觉性别二型性物种中听力男性和聋女性之间的发育差异，强调保幼激素和蜕皮激素的作用。该项目试图证实这样一个假设，即许多看似不同的昆虫耳朵实际上是从昆虫身体上完全相同的结构独立进化而来的。因此，身体上适合制造耳朵的进化热点数量非常有限。免疫染色将被用来绘制一些鼓形昆虫腹部和胸部的脉管器官分布图，以准确地确定哪些脉管器官已经成为鼓膜器官--预计90个以上的脉管器官中有3到4个占大多数昆虫的耳朵。这一系列研究将使人们更清楚地了解神经和非神经特征，这些特征定义了听觉系统进化的热点。

This research seeks to discover what changes occur in the sensory periphery and the CNS during the evolutionary transition between earless and eared (hearing) animals. What are the underlying mechanoreceptive peripheral and CNS substrates for hearing? Do new processing circuits arise specifically for hearing and acoustic behaviors? Or do the afferents from the new sensory system link to existing circuits? Insect systems provide an excellent model for studying these questions since the fundamental structures of auditory receptors and ears are remarkably similar in vertebrates and invertebrates. Further, hearing has evolved many times in insects (greater than 14 compared with less than 3 in vertebrates) so there are many parallel cases to compare and contrast in search of fundamental rules for the evolution of a new auditory system. Praying mantises, the focal animal of the project, are unique in possessing a single, ultrasound-sensitive ear in the ventral midline of the body. Previous research has identified the homologs of auditory system components in the mantis closest sister group, cockroaches (without tympanate hearing) and has detailed the nymphal development of the mantis ear. The current project will define the transition in behaviors-from non-acoustic (cockroach; mantis nymphs before hearing develops) to acoustic (adult mantis)-that must accompany the acquisition of hearing. This will be accompanied by an examination of the physiology of auditory internuerons and their homologs as a first step in understanding the CNS circuitry changes underlying the behavioral changes. The project will study the evolution of ontogenetic paths that have led to different auditory capabilities among mantises. It will focus on the developmental contrast between hearing males and deaf females in species with auditory sexual dimorphism, emphasizing the role of juvenile hormone and ecdysteroids. The project seeks to substantiate the hypothesis that many seemingly disparate insect ears have, in fact, evolved independently from exactly the same structures on the insect body. Thus, there are a very limited number of evolutionary hot spots on the body suitable for building an ear. Immunostaining will be used to map chordotonal organ distribution in the abdomen and thorax of a number of tympanate insects to determine exactly which chordotonal organs have become tympanal organs-the expectation is that three or four chordotonal organs out of greater than 90 account for most insect ears. This line of research will lead to a clearer understanding of the neural and non-neural characteristics that define a hot spot for auditory system evolution.