Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia
J Exp Biol. 2019 Jun 19;222(Pt 12):jeb203018. doi: 10.1242/jeb.203018.
Vision is crucial for animals to find prey, locate conspecifics and navigate within cluttered landscapes. Animals need to discriminate objects against a visually noisy background. However, the ability to detect spatial information is limited by eye size. In insects, as individuals become smaller, the space available for the eyes reduces, which affects the number of ommatidia, the size of the lens and the downstream information-processing capabilities. The evolution of small body size in a lineage, known as miniaturisation, is common in insects. Here, using pattern electroretinography with vertical sinusoidal gratings as stimuli, we studied how miniaturisation affects spatial resolving power and contrast sensitivity in four diurnal ants that live in a similar environment but vary in their body and eye size. We found that ants with fewer and smaller ommatidial facets had lower spatial resolving power and contrast sensitivity. The spatial resolving power was maximum in the largest ant at 0.60 cycles deg compared with that of the ant with smallest eyes at 0.48 cycles deg Maximum contrast sensitivity (minimum contrast threshold) in (2627 facets) was 15.51 (6.4% contrast detection threshold) at 0.1 cycles deg, while the smallest ant (227 facets) had a maximum contrast sensitivity of 1.34 (74.1% contrast detection threshold) at 0.05 cycles deg Miniaturisation thus dramatically decreases maximum contrast sensitivity and also reduces spatial resolution, which could have implications for visually guided behaviours. This is the first study to physiologically investigate contrast sensitivity in the context of insect allometry.
视觉对于动物寻找猎物、定位同种个体和在杂乱的环境中导航至关重要。动物需要在视觉嘈杂的背景下辨别物体。然而，检测空间信息的能力受到眼睛大小的限制。在昆虫中，随着个体变得越来越小，眼睛的可用空间减少，这会影响小眼数量、透镜的大小以及下游的信息处理能力。在一个谱系中，小体型的进化，即小型化，在昆虫中很常见。在这里，我们使用垂直正弦光栅作为刺激的模式视网膜电图来研究小型化如何影响四种在相似环境中生活但身体和眼睛大小不同的昼行蚂蚁的空间分辨率和对比敏感度。我们发现，小眼数量较少和较小的蚂蚁的空间分辨率和对比敏感度较低。最大的蚂蚁的空间分辨率最高，为 0.60 个周期/度，而眼睛最小的蚂蚁的空间分辨率为 0.48 个周期/度。最大对比度灵敏度（最小对比度检测阈值）在 （2627 个小面）为 0.1 个周期/度时为 15.51（6.4%对比度检测阈值），而最小的蚂蚁 （227 个小面）在 0.05 个周期/度时最大对比度灵敏度为 1.34（74.1%对比度检测阈值）。因此，小型化极大地降低了最大对比度灵敏度，也降低了空间分辨率，这可能对视觉引导的行为产生影响。这是首次在昆虫比例关系的背景下对对比敏感度进行生理研究的研究。
