Department of Biology, University of Maryland, College Park, MD 20742, USA
Department of Biology, University of Maryland, College Park, MD 20742, USA.
J Exp Biol. 2019 Sep 3;222(Pt 17):jeb201160. doi: 10.1242/jeb.201160.
Color vision is essential for animals as it allows them to detect, recognize and discriminate between colored objects. Studies analyzing color vision require an integrative approach, combining behavioral experiments, physiological models and quantitative analyses of photoreceptor stimulation. Here, we demonstrate, for the first time, the limits of chromatic discrimination in , a rock-dwelling cichlid from Lake Malawi, using behavioral experiments and visual modeling. Fish were trained to discriminate between colored stimuli. Color discrimination thresholds were quantified by testing fish chromatic discrimination between the rewarded stimulus and distracter stimuli that varied in chromatic distance (Δ). This was done under fluorescent lights alone and with additional violet lights. Our results provide two main outcomes. First, cichlid color discrimination thresholds correspond with predictions from the receptor noise limited (RNL) model but only if we assume a Weber fraction higher than the typical value of 5%. Second, cichlids may exhibit limited color constancy under certain lighting conditions as most individuals failed to discriminate colors when violet light was added. We further used the color discrimination thresholds obtained from these experiments to model color discrimination of actual fish colors and backgrounds under natural lighting for Lake Malawi. We found that, for , blue is most chromatically contrasting against yellows and space-light, which might be important for discriminating male nuptial colorations and detecting males against the background. This study highlights the importance of lab-based behavioral experiments in understanding color vision and in parameterizing the assumptions of the RNL vision model for different species.
颜色视觉对于动物至关重要，因为它使动物能够检测、识别和区分有色物体。分析颜色视觉的研究需要综合的方法，结合行为实验、生理模型和对光感受器刺激的定量分析。在这里，我们首次展示了马拉维湖岩石栖息的慈鲷 的色觉辨别极限，使用行为实验和视觉建模。鱼被训练来区分颜色刺激。通过测试鱼在奖励刺激和在颜色上有差异的干扰刺激（Δ）之间的色觉辨别，量化色觉辨别阈值。这是在荧光灯下单独进行的，并且加入了额外的紫光。我们的结果提供了两个主要结果。首先，慈鲷的颜色辨别阈值与从感受器噪声限制（RNL）模型得出的预测相符，但前提是我们假设韦伯分数高于典型值 5%。其次，在某些光照条件下，慈鲷可能表现出有限的颜色恒常性，因为大多数个体在加入紫光时无法辨别颜色。我们进一步使用这些实验中获得的颜色辨别阈值来模拟马拉维湖自然光照下实际鱼类颜色和背景的颜色辨别。我们发现，对于 来说，蓝色与黄色和空间光的颜色对比最鲜明，这对于区分雄性婚色和在背景中发现雄性可能很重要。这项研究强调了基于实验室的行为实验在理解颜色视觉和为不同物种的 RNL 视觉模型参数化方面的重要性。
