Spiders in Aussie cities undergoing 'terrifying' change

Spiders living in an Australian capital city are undergoing a “terrifying” physiological change. Researchers have discovered artificial light is causing the brains of at least one species to shrink, impacting areas associated with vision and hormonal regulation.

They believe lights around Melbourne are interfering with the melatonin in garden orb-weaving spiders, a chemical that helps animals maintain their natural day and night rhythm. But when it’s light all the time, production in the body drops and this has consequences.

“It can have knock-on effects for immunity, a whole suite of things related to physiology, and possibly neural repair, neural development of organs like the brain, for example,” author and Melbourne University animal behaviour expert Professor Therésa Jones told Yahoo News.

Is light pollution changing how spiders behave?

While it’s too early to know whether light is impacting the behaviour of spiders, there is some indication climbing behaviour could be affected, although this hasn’t been directly linked to the decline in brain size.

Researchers think it is likely the impact on spiders of light pollution isn’t just linked to one species and one city, as separate studies have shown that artificial light is impacting most animals.

“I’ve been working in light pollution for 10 years now, and the more I learn, the more terrifying it is,” Jones said.

“Light pollution has so dramatically transformed something that's been so constant for so long – natural light cycles. We as humans, as animals, plants, bacteria, we're so governed by light. During the daytime we wake, and at nighttime we sleep. It governs seasonality. It controls so many things that changing it so dramatically is problematic.”

Blue light the most problematic for spiders and other animals

Because blue light is the most disruptive when it comes to melatonin production, when councils replaced their traditional yellow lights with LEDs this intensified the problem. Although many are now working to phase in new LEDs that have a phosphorus coating that cuts out the blue.

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Communities around the country are increasingly aware of the impact of blue light, and as a result there has been a rapid uptake of glasses which block it out. And Jones describes them as an essential tool for mitigating damage.

“There’s fairly good evidence now linking it to impacts on certain groups. For instance, night shift workers tend to have much higher incidences of cancers, depression, a whole suite of pathologies, we think are associated with light,” Jones said.

She added, “Medicine has been talking about the impact of light at night for a long time, and to be honest ecology came to the party quite late.”

The effects of artificial light at night on spider brains has been published by the Royal Society in the journal Biology Letters.

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