As an obligate ectoparasite of bats, the bat fly Trichobius frequens (Diptera: Streblidae) inhabits the same subterranean environment as their nocturnal bat hosts. In this study, we characterize the macromorphology, optical architecture, rhabdom anatomy, photoreceptor absorbance, and opsin expression of the significantly reduced visual system in T. frequens resulting from evolution in the dark. The eyes develop over a 21–22 day pupal developmental period, with pigmentation appearing on pupal day 11. After eclosion as an adult, T. frequens eyes consist of on average 8 facets, each overlying a fused rhabdom consisting of anywhere from 11 to 18 estimated retinula cells. The dimensions of the facets and fused rhabdoms are similar to those measured in other nocturnal insects. T. frequens eyes are functional as shown by expression of a Rh1 opsin forming a visual pigment with a peak sensitivity to 487 nm, similar to other dipteran Rh1 opsins. Future studies will evaluate how individuals with such reduced capabilities for spatial vision as well as sensitivity still capture enough visual information to use flight to maneuver through dark habitats.

作为蝙蝠的一种专性体外寄生虫，蝙蝠蝇Trichobius frequens（双翅目：Streblidae）与其夜间活动的蝙蝠宿主栖息在相同的地下环境中。在这项研究中，我们表征了在黑暗中进化导致T.frequens 中显着减少的视觉系统的宏观形态学、光学结构、横纹肌解剖、光感受器吸光度和视蛋白表达。眼睛发育超过 21-22 天的蛹发育期，色素沉着出现在蛹的第 11 天。成年羽化后，T. frequens眼睛平均由 8 个小平面组成，每个小平面上覆盖着一个融合的横纹肌，该横纹肌由 11 到 18 个估计的视网膜细胞组成。小面和融合横纹的尺寸与在其他夜行昆虫中测量的尺寸相似。与其他双翅目 Rh1 视蛋白类似，T. frequens眼睛的功能表现为 Rh1 视蛋白的表达，该视蛋白形成对 487 nm 具有峰值灵敏度的视觉色素。未来的研究将评估空间视觉能力和敏感性降低的个体如何仍然捕获足够的视觉信息，以利用飞行在黑暗的栖息地中进行机动。