A sexual dimorphism in the spatial vision of North American band-winged grasshoppers

Visual acuity (VA) --- a measurement of the fineness or coarseness of vision --- may vary within a species including between the biological sexes. Although numerous studies have found males with finer VA than females, relatively few have shown the opposite with females having finer vision. This is surprising because our understanding of between species differences in VA suggests that females may have finer vision than males if they 1) are larger than males, or 2) need finer vision to detect and/or discriminate between males. Here, we estimate the interommatidial angle (∆Φ, an anatomical measurement of VA) in three species of band-winged grasshoppers in which females are both the larger sex and likely interpret visual signals (Arphia pseudonietana, Dissosteira carolina, and Spharagemon equale; total n = 98). Using a radius of curvature estimation method, we find that females have ~19% finer estimated ∆Φ than males in the most acute region and axis of the eye, but that this dimorphism var...视敏度（Visual Acuity, VA）——即对视觉精细度的量化衡量指标——在同一物种内可存在个体差异，其中也包括不同生物学性别之间的差异。尽管诸多研究已证实雄性的视敏度优于雌性，但极少有研究得出相反结论，即雌性拥有更敏锐的视觉。这一现象颇为出人意料，因为我们对不同物种间视敏度差异的认知表明，若雌性满足以下任一条件，其视敏度或可优于雄性：1）体型大于雄性；或2）需要更敏锐的视觉来检测或辨别雄性个体。本研究针对三种斑翅蚱蜢展开，其中雌性均为体型更大的性别，且具备视觉信号解读能力（Arphia pseudonietana、Dissosteira carolina及Spharagemon equale；总样本量n=98），我们通过曲率半径估算法估算了其小眼间角（interommatidial angle, ∆Φ，一种评估视敏度的解剖学指标）。研究发现，在眼睛最敏锐的区域与轴向上，雌性的估算∆Φ较雄性低约19%，即视敏度更优，但这种视觉二态性存在差异……