Overcoming the loss of blue sensitivity through opsin duplication in the largest animal group, beetles

Camilla R Sharkey,Nathan P Lord,Gavin J Martin,Seth M Bybee,M Stanley Fujimoto,Seunggwan Shin,Anton Suvorov,Duane D Mckenna

doi:10.1038/s41598-017-00061-7

Camilla R Sharkey, Nathan P Lord + Show 6 more

Open Access

https://doi.org/10.1038/s41598-017-00061-7

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Abstract

Opsin proteins are fundamental components of animal vision whose structure largely determines the sensitivity of visual pigments to different wavelengths of light. Surprisingly little is known about opsin evolution in beetles, even though they are the most species rich animal group on Earth and exhibit considerable variation in visual system sensitivities. We reveal the patterns of opsin evolution across 62 beetle species and relatives. Our results show that the major insect opsin class (SW) that typically confers sensitivity to “blue” wavelengths was lost ~300 million years ago, before the origin of modern beetles. We propose that UV and LW opsin gene duplications have restored the potential for trichromacy (three separate channels for colour vision) in beetles up to 12 times and more specifically, duplications within the UV opsin class have likely led to the restoration of “blue” sensitivity up to 10 times. This finding reveals unexpected plasticity within the insect visual system and highlights its remarkable ability to evolve and adapt to the available light and visual cues present in the environment.

Highlights

At the molecular level, the wavelength sensitivity of an animal photoreceptor is determined by the photopigment, comprising an opsin protein bound to a light-absorbing chromophore
While the majority of samples were derived from adult tissue (Table S1), larval tissue was sequenced for 11 species
The SW opsin class was not recovered from these samples, indicating that it has been lost in both major life stages

Summary

Introduction

The wavelength sensitivity of an animal photoreceptor is determined by the photopigment, comprising an opsin protein bound to a light-absorbing chromophore. In the case of opsins, beneficial mutations in duplicates may lead to changes in photopigment properties, such as spectral sensitivity. Such duplications alongside losses of opsins have shaped the major animal opsin classes we observe today. It has been proposed that all beetles may lack the SW opsin class, which typically underpins visual sensitivity to blue wavelengths in insects. The SW opsin class was lost independently in numerous beetle lineages, or secondly, this opsin class was lost prior to or during the early evolutionary history of beetles and blue light sensitivity was regained multiple times, independently of the ancestral SW opsin. Exemplars from the closely related orders Strepsiptera (twisted-wing parasites), Raphidioptera (snake flies), Megaloptera (alderflies, fishflies and dobsonflies) and Neuroptera (lacewings, antlions and mantidflies), comprising the other major lineages of the clade Neuropteroidea[19] were investigated

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