Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK.
Integrative Biology and Physiology, UCLA, Los Angeles, CA, 90095, USA.
BMC Biol. 2024 Mar 19;22(1):67. doi: 10.1186/s12915-024-01864-7.
Insects have evolved complex visual systems and display an astonishing range of adaptations for diverse ecological niches. Species of Drosophila melanogaster subgroup exhibit extensive intra- and interspecific differences in compound eye size. These differences provide an excellent opportunity to better understand variation in insect eye structure and the impact on vision. Here we further explored the difference in eye size between D. mauritiana and its sibling species D. simulans.
We confirmed that D. mauritiana have rapidly evolved larger eyes as a result of more and wider ommatidia than D. simulans since they recently diverged approximately 240,000 years ago. The functional impact of eye size, and specifically ommatidia size, is often only estimated based on the rigid surface morphology of the compound eye. Therefore, we used 3D synchrotron radiation tomography to measure optical parameters in 3D, predict optical capacity, and compare the modelled vision to in vivo optomotor responses. Our optical models predicted higher contrast sensitivity for D. mauritiana, which we verified by presenting sinusoidal gratings to tethered flies in a flight arena. Similarly, we confirmed the higher spatial acuity predicted for Drosophila simulans with smaller ommatidia and found evidence for higher temporal resolution.
Our study demonstrates that even subtle differences in ommatidia size between closely related Drosophila species can impact the vision of these insects. Therefore, further comparative studies of intra- and interspecific variation in eye morphology and the consequences for vision among other Drosophila species, other dipterans and other insects are needed to better understand compound eye structure-function and how the diversification of eye size, shape, and function has helped insects to adapt to the vast range of ecological niches.
昆虫已经进化出复杂的视觉系统，并表现出对各种生态位的惊人适应能力。黑腹果蝇亚组的物种在复眼大小上表现出广泛的种内和种间差异。这些差异为更好地了解昆虫眼睛结构的变化以及对视觉的影响提供了极好的机会。在这里，我们进一步探索了毛里求斯果蝇与其姊妹种拟暗果蝇在眼睛大小上的差异。
我们证实，毛里求斯果蝇由于具有比拟暗果蝇更多和更宽的小眼，眼睛迅速进化得更大，因为它们最近在大约 24 万年前就已经分化了。眼睛大小的功能影响，特别是小眼大小的功能影响，通常只是基于复眼的刚性表面形态来估计的。因此，我们使用 3D 同步辐射断层扫描来测量 3D 中的光学参数，预测光学能力，并将模型化的视觉与体内的运动反应进行比较。我们的光学模型预测毛里求斯果蝇的对比度敏感性更高，我们通过在飞行竞技场中向系绳的果蝇呈现正弦光栅来验证了这一点。同样，我们通过证实小眼较小的拟暗果蝇预测的更高空间分辨率，证实了预测的更高空间分辨率。
我们的研究表明，即使在密切相关的果蝇物种之间，小眼大小的微小差异也会影响这些昆虫的视觉。因此，需要进一步研究其他果蝇物种、其他双翅目昆虫和其他昆虫的眼睛形态的种内和种间变异以及对视觉的影响，以更好地了解复眼的结构-功能，以及眼睛大小、形状和功能的多样化如何帮助昆虫适应广泛的生态位。
