Scientists have long grappled with the question of why some tarantulas – an animal most active during nocturnal hours – sport very vivid shades of blue and green on their bodies, especially as it was believed that they are incapable of differentiating between colours or truly perceiving colours visually.
New research from Yale-NUS College and Carnegie Mellon University (CMU) reveals that, contrary to previous belief, these bulky spiders have the ability to see in colour and suggest that the blue and green colouration may serve specific purposes.
Some tarantulas are vivid blue or green colours.
The research team led by Dr Saoirse Foley (CMU) and Dr Vinod Kumar Saranathan (Yale-NUS) found support for new hypotheses that tarantulas’ vibrant blue colours may be used to communicate with potential mating partners – meaning they are not colourblind – and green colouration allows the arachnids to conceal themselves among foliage.
In the study, published in the Proceedings of the Royal Society B, the researchers analysed the expression patterns of opsins, a light sensitive-protein often present in animals’ eyes that determines how they perceive colour.
Researchers found that most tarantulas have an opsin array that is similar to that of spiders with colour vision, that are active in the daytime. Therefore, tarantulas may be able to see the bright blue colours displayed by other tarantulas.
The scientists say that ancient tarantulae from 110 million years ago were most likely also blue after they reconstructed the colours using comparative phylogenetic analyses.
They also found that blue colouration does not serve as a defence mechanism, which suggests that the evolution might be a mating call because it is not a predator deterrent.
The presence of green colouration is dependent on whether the species is tree-dwelling, which suggests that the colour serves as camouflage.
According to Dr Foley: ‘While the precise function of blueness remains unclear, our results suggest that tarantulas may be able to see these blue displays, so mate choice is a likely potential explanation. We have set an impetus for future projects to include a behavioural element to fully explore these hypotheses, and it is very exciting to consider how further studies will build upon our results.’
Image credit: Pixabay
