Glass knifefish (Eigenmannia) are a group of weakly electric fishes found throughout the Amazon basin. Their electric organ discharges (EODs) are energetically costly adaptations used in social communication and for localizing conspecifics and other objects including prey at night and in turbid water. Interestingly, a troglobitic population of blind cavefish Eigenmannia vicentespelea survives in complete darkness in a cave system in central Brazil. We examined the effects of troglobitic conditions, which includes a complete loss of visual cues and potentially reduced food sources, by comparing the behavior and movement of freely behaving cavefish to a nearby epigean (surface) population (Eigenmannia trilineata). We found that the strengths of electric discharges in cavefish were greater than in surface fish, which may result from increased reliance on electrosensory perception, larger size, and sufficient food resources. Surface fish were recorded while feeding at night and did not show evidence of territoriality, whereas cavefish appeared to maintain territories. Surprisingly, we routinely found both surface and cavefish with sustained differences in EOD frequencies that were below 10 Hz despite being within close proximity of about 50 cm. A half century of analysis of electrosocial interactions in laboratory tanks suggest that these small differences in EOD frequencies should have triggered the “jamming avoidance response,” a behavior in which fish change their EOD frequencies to increase the difference between individuals. Pairs of fish also showed significant interactions between EOD frequencies and relative movements at large distances, over 1.5 m, and at high differences in frequencies, often >50 Hz. These interactions are likely “envelope” responses in which fish alter their EOD frequency in relation to higher order features, specifically changes in the depth of modulation, of electrosocial signals.

玻璃刀鱼（本征狂）是在整个亚马逊河流域发现的一组弱电鱼。它们的电子器官放电（EOD）耗费大量能源，用于社交交流中，用于定位特定物种和其他物体，包括夜间和浑水中的猎物。有趣的是，盲眼穴居人的穴居群本生草在巴西中部的洞穴系统中完全黑暗中生存。我们通过比较行为自由的穴居鱼与附近的Epigean（表层）种群的行为和运动，检查了穴居条件的影响，其中包括视觉提示的完全丧失和潜在的食物来源减少（三叶本色）。我们发现，穴居鱼类的放电强度要比表面鱼类更大，这可能是由于对电感应感知的依赖性增加，尺寸更大以及食物资源充足所致。在夜间喂食时记录了表层鱼类，没有显示出地域性的证据，而穴居鱼似乎保持了其领土。出乎意料的是，我们常规地发现表层和洞穴鱼的EOD频率均存在持续差异，尽管相距约50厘米，但仍低于10 Hz。半个世纪以来，对实验室水箱中电社会互动的分析表明，EOD频率的这些细微差异应该触发了“干扰避免反应”，即鱼类改变其EOD频率以增加个体之间差异的行为。成对的鱼还表现出EOD频率与距离超过1.5 m的远距离和较高频率差异（通常> 50 Hz）之间的相对运动之间存在显着的相互作用。这些相互作用可能是“包络”响应，在这种响应中，鱼类会改变其与社会电信号的高级特征（特别是调制深度的变化）有关的EOD频率。