Nutrition-induced macular-degeneration-like photoreceptor damage in jumping spider eyes.

Age-related macular degeneration (AMD) is a leading cause of vision loss in humans. Despite its prevalence and medical significance, many aspects of AMD remain elusive and treatment options are limited. Here, we present data that suggest jumping spiders offer a unique opportunity for understanding the fundamentals underlying retinal degeneration, thereby shedding light on a process that impacts millions of people globally. Using a micro-ophthalmoscope and histological evidence, we demonstrate that significant photoreceptor damage can occur during development in the image-forming anterior lateral eyes of the jumping spider Phidippus audax. Furthermore, we find that this photoreceptor degeneration is exacerbated by inadequate nutrition and is most prevalent in the high-density region of the retina, like AMD in humans. This suggests that similar to those in vertebrates, the retinas in P. audax are challenged to meet high-energy cellular demands.

Growing tiny eyes: How juvenile jumping spiders retain high visual performance in the face of size limitations and developmental constraints.

Adult jumping spiders are known for their extraordinary eyesight and complex, visually guided behaviors, including elaborate communicatory displays, navigational abilities, and prey-specific predatory strategies. Juvenile spiders also exhibit many of these behaviors, yet their visual systems are many times smaller. How do juveniles retain high visually guided performance despite severe size constraints on their visual systems? We investigated developmental changes in eye morphology and visual function in the jumping spider Phidippus audax using morphology, histology, ophthalmoscopy, and optical measurements. We find that juvenile spiders have proportionally larger lenses in relation to their body size than adults. This should alleviate some of the costs of small body size on visual function. However, photoreceptor number in the anterior lateral eyes (ALE) remains constant from early development onward, consistent with a developmental constraint on photoreceptor differentiation. To accommodate these photoreceptors within the diminutive volume of the spiderling cephalothorax, ALE rhabdoms in early life stages are more tightly packed and significantly smaller in diameter and length, properties that expand across development. Lens focal lengths increase as eyes and retinas grow, resulting in a remarkable maintenance of ALE spatial acuity and field-of-view across life stages. However, this maintenance of acuity comes at a sensitivity cost given the small rhabdomal volumes required by space constraints early in life. Taken together, our results indicate that young jumping spiders have eyes already equipped for high acuity vision, but these young spiders may struggle to perform visually demanding behaviors in low-light environments, a notion that warrants further testing.