Adaptations of the Vertebrate Retina to Low-Light Conditions: A Review.

Vision is a critical sensory modality in vertebrates, enabling diverse adaptations to environmental challenges. This review explores the remarkable adaptations of vertebrate eyes to low-light environments, such as nocturnal habitats, deep-sea ecosystems and subterranean niches. Key structural and functional modifications include enhanced eye size, rod-dominated retinas, reflective tapetal layers and photopigment spectral tuning. The role of photoreceptor specialisation and retinomotor movements in optimising photon capture and minimising light scatter is examined, alongside evolutionary trade-offs that prioritise sensitivity over resolution. Furthermore, adaptations such as bioluminescence detection in deep-sea fish and the regressive evolution of vision in subterranean species highlight the intricate relationship between ecological demands and visual evolution. By synthesising current research, this review provides insights into the evolution in vertebrate visual systems and offers future perspectives on the molecular and ecological drivers of these adaptations.