Visually dependent dim-light foraging has evolved repeatedly, broadening the ecological niches of some species. Many dim-light foraging lineages evolved from diurnal ancestors, requiring immense visual sensitivity increases to compensate for light levels a billion times dimmer than daylight. Some taxa, such as bees, are anatomically constrained by apposition compound eyes, which function well in daylight but not in starlight. Even with this constraint, the bee genus Megalopta has incredibly sensitive eyes, foraging in light levels up to nine orders of magnitude dimmer than diurnal relatives. Despite many behavioural studies, variation in visual sensitivity and eye morphometry has not been investigated within and across Megalopta species. Here we quantify external eye morphology (corneal area and facet size) for sympatric species of Megalopta, M. genalis and M. amoena, which forage during twilight. We use electroretinograms to show that males, despite being smaller than females, have equivalent visual sensitivity and increased retinal responsivity. Although males have relatively larger eyes compared with females, corneal area and facet size were not correlated with retinal responsivity, suggesting that males have additional non-morphological adaptations to increase retinal responsiveness. These findings provide the foundation for future work into the neural and physiological mechanisms that interface with morphology to influence visual sensitivity, with implications for understanding niche exploitation.

中文翻译：

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两种葫芦毛蜂的眼睛形态和视觉响应能力的物种和性别差异（Megalopta spp。，Hymenoptera：Halictidae）

依赖视觉的暗光觅食已经反复发展，拓宽了某些物种的生态位。许多暗光觅食谱系是由昼夜祖先演化而来的，需要极大的视觉灵敏度来补偿比日光昏暗十亿倍的光照水平。一些类群（例如蜜蜂）在解剖学上受到并置复眼的约束，这些复眼在日光下效果很好，但在星光下效果不佳。即使有这种限制，蜜蜂属Megalopta的眼睛仍然具有令人难以置信的敏感度，它们的光照强度要比昼夜亲戚高9个数量级。尽管进行了许多行为研究，但尚未对Megalopta内及其之间的视觉敏感性和眼部形态变化进行调查。种类。在这里，我们量化外眼形态（角膜面积和小面大小）的域物种Megalopta，M. genalis和M.豌豆，在暮色中觅食。我们使用视网膜电图显示，尽管雄性比雌性小，但它们具有同等的视觉敏感度并增加了视网膜反应性。尽管与女性相比，男性的眼睛相对较大，但角膜面积和小平面大小与视网膜反应性无关，这表明男性具有其他非形态学适应性，可以增加视网膜反应性。这些发现为将来的神经和生理机制的研究提供了基础，这些机制与形态相互作用以影响视觉敏感性，并有助于了解利基市场。