Mason AC, Forrest TG, Hoy RR
Department of Neurobiology and Behavior, S. G. Mudd Hall, Cornell University, Ithaca, NY 14853, USA.
J Exp Biol. 1998 May 21;201 (Pt 12):1967-79.
We have studied auditory responses in two species of mole cricket (Scapteriscus borellii and S. abbreviatus) to determine (1) whether they show sensitivity to ultrasound, (2) whether their hearing (at both low and high frequencies) is based on the same neural circuitry as that of true crickets, and (3) whether ultrasound sensitivity in different mole cricket species varies with their ability to fly. S. borellii are sensitive to ultrasonic frequencies. There is evidence of a segregation of frequency bands in prothoracic auditory neurons. There are two pairs of &ohgr ; neurons (ONs) with similar morphology to ON1 of true crickets. The two pairs of ONs differ in tuning. One pair has two sensitivity peaks: at the frequency of the calling song of this species (3 kHz), and in the ultrasonic range (25 kHz). The other pair lacks the high-frequency sensitivity and responds exclusively to frequencies in the range of the species song. These two types are not morphologically distinguishable. In S. abbreviatus, only one class of ON was found. S. abbreviatus ONs are narrowly tuned to the frequency of the species' calls. A T-neuron had the best ultrasonic frequency sensitivity in S. borellii. This cell showed a broad tuning to ultrasonic frequencies and was inhibited by low-frequency stimuli. A morphologically similar neuron was also recorded in S. abbreviatus, but lacked the high-frequency sensitivity peak of that in S. borellii. We also assessed the responses of flying S. borellii to ultrasound using field playbacks to free-flying animals. The attractiveness of broadcast calling song was diminished by the addition of an ultrasound signal, indicating that S. borellii avoid high-frequency sound. The results indicate that mole crickets process low-frequency auditory stimuli using mechanisms similar to those of true crickets. They show a negative behavioural response to high-frequency stimuli, as do true crickets, but the organization of ultrasound-sensitive auditory circuitry in mole crickets differs from that of true crickets.
我们研究了两种蝼蛄（博氏蝼蛄和短翅蝼蛄）的听觉反应，以确定：（1）它们是否对超声波敏感；（2）它们的听觉（低频和高频）是否与真正的蟋蟀基于相同的神经回路；（3）不同蝼蛄物种的超声波敏感性是否随其飞行能力而变化。博氏蝼蛄对超声频率敏感。有证据表明前胸听觉神经元存在频带分离。有两对与真正蟋蟀的ON1形态相似的ω神经元（ONs）。这两对ONs的调谐不同。一对有两个灵敏度峰值：在该物种的求偶歌声频率（3千赫）和超声波范围内（25千赫）。另一对缺乏高频敏感性，仅对该物种歌声范围内的频率作出反应。这两种类型在形态上无法区分。在短翅蝼蛄中，只发现了一类ON。短翅蝼蛄的ONs对该物种叫声的频率调谐很窄。在博氏蝼蛄中，一个T神经元具有最佳的超声频率敏感性。该细胞对超声频率表现出广泛的调谐，并受到低频刺激的抑制。在短翅蝼蛄中也记录到了一个形态相似的神经元，但缺乏博氏蝼蛄中该神经元的高频敏感性峰值。我们还通过向自由飞行的动物进行野外回放来评估飞行中的博氏蝼蛄对超声波的反应。添加超声波信号会降低广播求偶歌声的吸引力，这表明博氏蝼蛄会避开高频声音。结果表明，蝼蛄处理低频听觉刺激的机制与真正的蟋蟀相似。它们对高频刺激表现出负面行为反应，与真正的蟋蟀一样，但蝼蛄中对超声波敏感的听觉回路的组织与真正的蟋蟀不同。
