Bumblebee visual allometry results in locally improved resolution and globally improved sensitivity

The quality of visual information that is available to an animal is limited by the size of its eyes. Differences in eye size can be observed even between closely related individuals, yet we understand little about how this affects vision. Insects are good models for exploring the effects of size on visual systems because many insect species exhibit size polymorphism. Previous work has been limited by difficulties in determining the 3D structure of eyes. We have developed a novel method based on x-ray microtomography to measure the 3D structure of insect eyes and to calculate predictions of their visual capabilities. We used our method to investigate visual allometry in the bumblebee Bombus terrestris and found that size affects specific aspects of vision, including binocular overlap, optical sensitivity, and dorsofrontal visual resolution. This reveals that differential scaling between eye areas provides flexibility that improves the visual capabilities of larger bumblebees.动物可获取的视觉信息质量，受其眼睛尺寸的制约。即便在亲缘关系极为相近的个体之间，也可观测到眼睛尺寸的差异，但目前学界对这类差异如何影响视觉功能的认知仍较为匮乏。昆虫是探究尺寸对视觉系统影响效应的理想模型，因诸多昆虫物种均存在体型多态性（size polymorphism）。过往相关研究受限于难以精准测定眼睛的三维结构。我们开发了一种基于X射线显微计算机断层扫描（X-ray microtomography）的全新方法，可用于测定昆虫眼睛的三维结构，并推导其视觉性能的预测结果。我们运用该方法对地熊蜂（Bombus terrestris）的视觉异速生长现象开展研究，结果发现体型会影响视觉的多个特定维度，包括双眼重叠视野、光学灵敏度以及额背区视觉分辨率。该研究揭示，眼睛各区域间的差异化缩放模式，可为体型更大的熊蜂带来视觉性能提升的灵活性。