Variability in the electrophysiological properties of homotypic photoreceptors is widespread and is thought to facilitate functioning under disparate illumination conditions. Compound eyes of insects have three sources of variability: inter-individual, intra-individual, and intra-ommatidial, the latter two overlapping. Here, I explored the causes of variability inPeriplaneta americana, a nocturnal insect characterized by highly variable photoreceptor responses. By recording from photoreceptors in dissociated ommatidia, including consecutive recordings from photoreceptors in the same ommatidium (SO), I studied the variability of six properties: whole-cell membrane capacitance (Cm), phototransduction latency, maximal conductance (Gmax) and the slope factor of the sustained Kv current, absolute sensitivity in dim light, and sustained light-induced current (LIC) amplitude in bright light. Coefficient of variation (CV) metrics were used to compare variances in four experimental groups: SO, same animal (SA), all data combined “full sample” (FS), and full sample of all SO recordings (FSSO). For the normally distributed parametersCm,Gmax, slope factor, and latency, the highest CV values were found in FS and FSSO, intermediate in SA, and the lowest in SO. On average, SO variance accounted for 47% of the full-sample variance in these four parameters. Absolute sensitivity and LIC values were not normally distributed, and the differences in variability between SO and FS/FSSO groups were smaller than for the other four parameters. These results indicate two main sources of variability, intra-ommatidial and inter-individual. Inter-individual variability was investigated by exposing adult cockroaches to constant light or dark for several months. In both groups, the majority of CV measures for the six parameters decreased compared to control, indicating substantial contribution of phenotypic plasticity to inter-individual differences. Analysis of variability of resting potential and elementary voltage responses revealed that resting potential is mainly determined by the sustained Kv conductance, whereas voltage bump amplitude is mainly determined by current bump amplitude andCm.

中文翻译：

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美洲大蠊视网膜电生理变异的来源

同型感光器的电生理特性的变异性很普遍，并且被认为有助于在不同的光照条件下发挥作用。昆虫的复眼具有三种变异来源：个体间、个体内和小眼内，后两者重叠。在这里，我探讨了可变性的原因美洲大蠊，一种夜间活动的昆虫，其特点是光感受器反应高度可变。通过从分离的小眼中的光感受器记录，包括来自同一小眼 (SO) 中光感受器的连续记录，我研究了六种特性的可变性：全细胞膜电容 (C米)、光转导潜伏期、最大电导 (G最大限度) 和持续 Kv 电流的斜率因子、暗光下的绝对灵敏度和强光下的持续光致电流 (LIC) 幅度。变异系数 (CV) 指标用于比较四个实验组的方差：SO、同一动物 (SA)、所有数据组合的“完整样本”(FS) 和所有 SO 记录的完整样本 (FSSO)。对于正态分布参数C米,G最大限度、斜率因子和潜伏期，在 FS 和 FSSO 中发现最高 CV 值，在 SA 中发现中间值，在 SO 中发现最低。平均而言，SO 方差占这四个参数中全样本方差的 47%。绝对敏感性和 LIC 值不是正态分布的，SO 和 FS/FSSO 组之间的变异性差异小于其他四个参数。这些结果表明了变异的两个主要来源，即小眼内和个体间。通过将成年蟑螂暴露在恒定的光照或黑暗中几个月来研究个体间的变异性。在两组中，与对照组相比，六个参数的大多数 CV 测量值均有所下降，表明表型可塑性对个体间差异有重大贡献。C米.