Jumping Spider Can Not Recognize Its Own Brightest Color

Jumping spiders have great sight, one attractive species appears to have a unique visual deficiency. According to new research, the jumping spider Saitis barbipes lacks photoreceptors capable of recognising the colour red. S. barbipes, such as many jumping spiders, has a vibrant coloration, with the male sporting brilliant splashes of rich, resplendent red. These crimson markings, which cover the top of his head and run down both of his back legs, are typically employed for mating and threat displays.

The researchers discovered photoreceptors for ultraviolet, blue, and green wavelengths in the spiders' retinas with microspectrophotometry, though no red photoreceptors. They also examined for filters that would change the colour of green photoreceptors to red, although they couldn't find any.

It appears to the spiders that what we perceive as red is simply an extension of their black patterns. Areas of ultraviolet appear to be visible, however they do not correspond to the patches of red.

Cynthia Tedore, biologist from the University of Hamburg in Germany said that males have bright red and black pigmentation on their forward-facing body surfaces, which they flaunt during courtship dances; females, on the other hand, have no red coloration at all. This led researchers to believe that the colour red must play a role in mate attraction. As such, they discovered that these spiders perceive red and black similarly, or nearly so, and that if red is recognised differently from black, it is perceived as a dark'spider green' rather than red.

As per the team's findings, they created a model of how predators with exclusively red vision, such as birds and lizards, may see the spiders and discovered that, at a distance, the red patches could mix with the black patterns, making the spider appear more brownish, similar to its leaf litter home. Such markings would have less distinction against a brown background if they were all the same hue.