Shaw S
J Exp Biol. 1994 Aug;193(1):13-47. doi: 10.1242/jeb.193.1.13.
Extracellular recordings from nerve 5 in metathoracic legs of Periplaneta americana disclose a sense organ that is extremely responsive to vibration but also detects sound (best response near 1.8 kHz) with a sensitivity similar to some insect auditory organs. The energy required from an auditory signal for a criterion response is similar or even smaller than for an optimal vibratory input. Responses originate in the subgenual organs (SGO) in the proximal tibiae, and cross-modal adaptation indicates that the same cells respond to both vibration and sound. Sound is picked up directly on some internal structure, not via sound-induced substratum vibration. Adaptation at different frequencies discloses no frequency-selectivity in the SGO. The nerve response is a burst of synchronized impulses at a frequency, fR, of approximately 300 Hz, that is practically invariant both with sound intensity and within the burst, suggesting that fR might represent some underlying resonance phenomenon, either of the SGO or of air in the tracheal system. The latter possibility is ruled out by observations made while the tracheae are perfused with HeO2. Similar responses can be recorded from the pro- and mesothoracic legs. Although Periplaneta is thought to be deaf and appears to ignore loud tones presented to the home colony, a more sensitive assay detects small leg movements in response to sound, confirming the presence of a functional auditory sense. The SGO is suspended from an expansion of the leg trachea, which may function to enhance sensitivity to vibration. This linkage preadapts the SGO to detect airborne sound transmitted in the tracheal system, and contact vibration may also stimulate the system in part by deforming the tracheae. It is proposed that auditory organs of crickets evolved from an ancestral SGO that already possessed dual responsiveness by subsequently developing effective vibration-isolating filters.
对美洲大蠊后胸腿的第5条神经进行细胞外记录，发现了一种感觉器官，它对振动极为敏感，但也能检测声音（在1.8千赫兹附近反应最佳），其灵敏度与一些昆虫听觉器官相似。产生标准反应所需的听觉信号能量与最佳振动输入所需能量相似甚至更小。反应起源于近端胫节的膝下器官（SGO），跨模态适应表明相同的细胞对振动和声音都有反应。声音是直接在某些内部结构上接收的，而不是通过声音引起的基质振动。不同频率下的适应情况表明，SGO没有频率选择性。神经反应是一串频率约为300赫兹的同步冲动，其频率fR实际上不随声音强度变化，在冲动串内也保持不变，这表明fR可能代表某种潜在的共振现象，要么是SGO的，要么是气管系统中空气的。当气管用氦氧灌注时的观察结果排除了后一种可能性。在前胸和中胸腿上也能记录到类似的反应。虽然美洲大蠊被认为是聋的，似乎会忽略向其栖息地发出的响亮音调，但一种更灵敏的检测方法能检测到腿部对声音的微小运动，证实了功能性听觉的存在。SGO悬挂在腿部气管的一个扩张部位，这可能起到增强对振动敏感度的作用。这种联系使SGO预先适应检测在气管系统中传播的空气传播声音，接触振动也可能部分通过使气管变形来刺激该系统。有人提出，蟋蟀的听觉器官是从一个已经具有双重反应能力的祖先SGO进化而来的，随后通过发展有效的振动隔离滤波器而形成。
