Daytime eyeshine contributes to pupil camouflage in a cryptobenthic marine fish

Ocular reflectors enhance eye sensitivity in dim light, but can produce reflected eyeshine when illuminated. Some fish can occlude their reflectors during the day. The opposite is observed in cryptic sit-and-wait predators such as scorpionfish and toadfish, where reflectors are occluded at night and exposed during the day. This results in daytime eyeshine, proposed to enhance pupil camouflage by reducing the contrast between the otherwise dark pupil and the surrounding tissue. In this study, we test this hypothesis in the scorpionfish Scorpaena porcus and show that eyeshine is the result of two mechanisms: the previously described Stratum Argenteum Reflected (SAR) eyeshine, and Pigment Epithelium Transmitted (PET) eyeshine, a newly described mechanism for this species. We confirm that the ocular reflector is exposed only when the eye is light-adapted, and present field measurements to show that eyeshine reduces pupil contrast against the iris. We then estimate the relative contribution ...眼部反光结构（ocular reflectors）可提升弱光环境下的眼部感光灵敏度，但在受光照时会产生反射性眼反光（eyeshine）。部分鱼类可在日间遮蔽其反光结构。而在鲉鱼、蟾鱼这类隐蔽性静候捕食者中则观察到相反现象：它们的反光结构会在夜间被遮蔽，日间则暴露出来。这种特性会产生日间眼反光，该现象被认为可通过降低原本暗沉的瞳孔与周围组织间的对比度，实现瞳孔的隐蔽伪装。本研究以欧洲黑鲉（Scorpaena porcus）为对象验证这一假说，结果表明眼反光由两种机制产生：此前已报道的银膜反射（Stratum Argenteum Reflected, SAR）眼反光，以及本研究首次在该物种中发现的色素上皮传递（Pigment Epithelium Transmitted, PET）眼反光。我们证实眼部反光结构仅在眼部处于光适应状态时才会暴露，并通过野外实测证明眼反光可降低瞳孔与虹膜间的对比度。后续我们将对各机制的相对贡献进行估算……