Sisneros Joseph A
Department of Psychology, University of Washington, Seattle, Washington 98195, USA.
J Neurophysiol. 2009 Aug;102(2):1121-31. doi: 10.1152/jn.00236.2009. Epub 2009 Jun 24.
The plainfin midshipman fish, Porichthys notatus, is a seasonally breeding species of marine teleost fish that generates acoustic signals for intraspecific social and reproductive-related communication. Female midshipman use the inner ear saccule as the main acoustic endorgan for hearing to detect and locate vocalizing males that produce multiharmonic advertisement calls during the breeding season. Previous work showed that the frequency sensitivity of midshipman auditory saccular afferents changed seasonally with female reproductive state such that summer reproductive females became better suited than winter nonreproductive females to encode the dominant higher harmonics of the male advertisement calls. The focus of this study was to test the hypothesis that seasonal reproductive-dependent changes in saccular afferent tuning is paralleled by similar changes in saccular sensitivity at the level of the hair-cell receptor. Here, I examined the evoked response properties of midshipman saccular hair cells from winter nonreproductive and summer reproductive females to determine if reproductive state affects the frequency response and threshold of the saccule to behaviorally relevant single tone stimuli. Saccular potentials were recorded from populations of hair cells in vivo while sound was presented by an underwater speaker. Results indicate that saccular hair cells from reproductive females had thresholds that were approximately 8 to 13 dB lower than nonreproductive females across a broad range of frequencies that included the dominant higher harmonic components and the fundamental frequency of the male's advertisement call. These seasonal-reproductive-dependent changes in thresholds varied differentially across the three (rostral, middle, and caudal) regions of the saccule. Such reproductive-dependent changes in saccule sensitivity may represent an adaptive plasticity of the midshipman auditory sense to enhance mate detection, recognition, and localization during the breeding season.
光腹后肛鱼（Porichthys notatus）是一种季节性繁殖的海洋硬骨鱼类，会发出声学信号用于种内社交和与繁殖相关的交流。雌性后肛鱼利用内耳球囊作为主要的听觉终器来检测和定位在繁殖季节发出多谐波求偶鸣叫的发声雄性。先前的研究表明，后肛鱼听觉球囊传入神经的频率敏感性会随着雌性生殖状态的变化而季节性改变，使得处于繁殖期的夏季雌性比处于非繁殖期的冬季雌性更适合编码雄性求偶鸣叫的主要高频谐波。本研究的重点是检验以下假设：球囊传入神经调谐的季节性生殖依赖性变化与毛细胞受体水平上球囊敏感性的类似变化平行。在这里，我研究了冬季非繁殖期和夏季繁殖期雌性后肛鱼球囊毛细胞的诱发反应特性，以确定生殖状态是否会影响球囊对行为相关单音刺激的频率反应和阈值。在通过水下扬声器发出声音时，在体内记录毛细胞群体的球囊电位。结果表明，在包括雄性求偶鸣叫的主要高频谐波成分和基频在内的广泛频率范围内，繁殖期雌性的球囊毛细胞阈值比非繁殖期雌性低约8至13分贝。球囊阈值的这些季节性生殖依赖性变化在球囊的三个区域（吻侧、中间和尾侧）有所不同。球囊敏感性的这种生殖依赖性变化可能代表了后肛鱼听觉的一种适应性可塑性，以在繁殖季节增强配偶的检测、识别和定位。
