Hungry eyes: Spiders lose vision when they're starving

Newswise —

Researchers at the University of Cincinnati have found that insufficiently nourished jumping spiders experience a loss of light-sensitive cells that are essential for their vision.

Elke Buschbeck, a professor at the UC College of Arts and Sciences, along with her colleagues, investigated the photoreceptors in the eyes of bold jumping spiders, which are small eight-legged predators that can be found throughout North America. These spiders heavily rely on their excellent eyesight to track and capture prey.

However, the researchers discovered that when jumping spiders are underfed, they start to lose the photoreceptors responsible for their exceptional eyesight. These findings have the potential to enhance our comprehension of how nutrition influences age-related vision impairments, including macular degeneration.

The researchers stumbled upon this discovery serendipitously while investigating the eyes of wild bold jumping spiders that were captured, utilizing their lab's custom-built ophthalmoscope, which can capture images of insects and spiders' retinas. They observed dark spots on the photoreceptors of some of the spiders, implying that they had degraded over the course of their lives or development.

“You could tell just by looking at them that some of the photoreceptors had died,” Buschbeck said.

"However, is the degeneration of photoreceptors truly occurring?" inquired Shubham Rathore, a doctoral candidate at UC. "Or are they merely becoming bleached due to our experimental methods?"

Rathore turned to electron microscopy to confirm that the cells indeed were dying.

The study suggests jumping spiders are a compelling model to study retinal and neuronal health.

Did poor nutrition cause it?

Miranda Brafford and John Goté, both UC alumni, investigated their hypothesis by conducting a study on two sets of captive spiders. One group received an unrestricted normal diet, while the other group was fed half-portions. The undernourished spiders experienced a higher loss of photoreceptors, particularly in the region of the retina with the highest concentration of them.

“It’s the functional equivalent of the macula in our eyes,” Buschbeck said.

That is the part of the eye that processes visual information directly in front of you.

"Photoreceptors have a high energy demand, making them energetically expensive," Buschbeck explained. "Without proper nutrition, it becomes difficult to sustain their energy requirements, leading to the failure of the system."

Approximately 20 million individuals in the United States are impacted by macular degeneration. This condition is the primary cause of age-related vision impairment and presently has no known cure.

Buschbeck noted, "What's intriguing is that macular degeneration in humans also exhibits indications of being associated with metabolic processes and challenges in delivering energy."

Rathore and Buschbeck expressed their desire to investigate whether the degeneration originates in the supportive tissues surrounding the photoreceptors and to identify the specific nutrients that promote optimal visual health.

Annette Stowasser, the lead author of the study and an assistant professor in UC's College of Arts and Sciences, cautioned against drawing direct comparisons between the vision deficits observed in spiders and those experienced by humans, stating that it is too early to do so.

Stowasser added, "Nevertheless, the fact that nutrient deprivation can produce the observed effects highlights the significance of closely monitoring the impact of nutrients."

Nathan Morehouse, one of the co-authors, serves as the director of UC's Institute for Research in Sensing and has researched the vision of jumping spiders worldwide.

Morehouse, who is also an associate professor in biological sciences, mused, "Wouldn't it be incredible if advancements in treatments for macular degeneration in humans were inspired by research on jumping spiders that are commonly found in backyards across the United States?"

“Sometimes answers to challenging problems can come from unexpected places,” he said.

The study was supported by grants from the National Science Foundation.