Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221, USA.
Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221, USA
J Exp Biol. 2020 Jan 6;223(Pt 1):jeb216192. doi: 10.1242/jeb.216192.
For proper function, vertebrate and invertebrate visual systems must be able to achieve and maintain emmetropia, a state where distant objects are in focus on the retina. In vertebrates, this is accomplished through a combination of genetic control during early development and homeostatic visual input that fine-tunes the optics of the eye. While emmetropization has long been researched in vertebrates, it is largely unknown how emmetropia is established in arthropods. We used a micro-ophthalmoscope to directly measure how the lens projects images onto the retina in the eyes of small, live arthropods, allowing us to compare the refractive states of light-reared and dark-reared arthropods. First, we measured the image-forming larval eyes of diving beetles (), which are known to grow rapidly and dramatically between larval instars. Then, we measured the image-forming principal anterior-median eyes of jumping spiders () after emergence from their egg cases. Finally, we measured individual ommatidia in the compound eyes of flesh flies () that had developed and emerged under either light or dark conditions. Surprisingly, and in sharp contrast to vertebrates, our data for this diverse set of arthropods suggest that visual input is inconsequential in regard to achieving well-focused eyes. Although it remains unclear whether visual input that is received after the initial development further improves focusing, these results suggest that at least the initial coordination between the lens refractive power and eye size in arthropods may be more strongly predetermined by developmental factors than is typically the case in vertebrates.
为了正常运作，脊椎动物和无脊椎动物的视觉系统必须能够实现并维持正视，即远处的物体在视网膜上清晰聚焦的状态。在脊椎动物中，这是通过早期发育过程中的遗传控制和精细调整眼球光学的稳态视觉输入相结合来实现的。虽然正视化在脊椎动物中已经研究了很长时间，但在节肢动物中如何建立正视化还知之甚少。我们使用微眼显微镜直接测量了小活体节肢动物眼睛中晶状体将图像投射到视网膜上的方式，从而可以比较光养和暗养节肢动物的屈光状态。首先，我们测量了潜水甲虫（）幼虫眼睛的成像，已知它们在幼虫期之间迅速而显著地生长。然后，我们测量了从卵囊中孵化出来的跳蛛（）的成像主前中眼。最后，我们测量了在光或暗条件下发育和出现的肉蝇（）复眼的单个小眼。令人惊讶的是，与脊椎动物形成鲜明对比的是，我们对这一系列不同节肢动物的数据表明，视觉输入对于实现良好聚焦的眼睛并不重要。虽然尚不清楚在初始发育后接收到的视觉输入是否会进一步改善聚焦，但这些结果表明，至少在节肢动物中，晶状体屈光力和眼睛大小之间的初始协调可能比通常在脊椎动物中更多地由发育因素预先确定。
