The diversity of opsins in Lake Baikal amphipods (Amphipoda: Gammaridae)

Polina Drozdova,Anton Gurkov,Maria Firulyova,Ekaterina Govorukhina,Alena Kizenko,Alexandra Saranchina,Maxim Timofeyev

doi:10.1186/s12862-021-01806-9

Abstract

BackgroundVision is a crucial sense for the evolutionary success of many animal groups. Here we explore the diversity of visual pigments (opsins) in the transcriptomes of amphipods (Crustacea: Amphipoda) and conclude that it is restricted to middle (MWS) and long wavelength-sensitive (LWS) opsins in the overwhelming majority of examined species.ResultsWe evidenced (i) parallel loss of MWS opsin expression in multiple species (including two independently evolved lineages from the deep and ancient Lake Baikal) and (ii) LWS opsin amplification (up to five transcripts) in both Baikal lineages. The number of LWS opsins negatively correlated with habitat depth in Baikal amphipods. Some LWS opsins in Baikal amphipods contained MWS-like substitutions, suggesting that they might have undergone spectral tuning.ConclusionsThis repeating two-step evolutionary scenario suggests common triggers, possibly the lack of light during the periods when Baikal was permanently covered with thick ice and its subsequent melting. Overall, this observation demonstrates the possibility of revealing climate history by following the evolutionary changes in protein families.

Highlights

Vision is a crucial sense for the evolutionary success of many animal groups
The diversity of opsin transcripts in different phylogenetic lineages of amphipods suggests multiple losses of middle wavelength-sensitive (MWS) opsins To obtain the first idea of visual opsin diversity in the transcriptomes of endemic Baikal amphipods, we searched for opsin transcripts in the 64 published transcriptome assemblies [47] with PIA3, a pipeline we modified from PIA2 [15]
The first hypothesis was tested by including in the analysis E. verrucosus, E. cyaneus, and G. lacustris assemblies based on whole-body material [48], which returned only long wavelength-sensitive (LWS) opsins (Additional file 1: Table S1)

Summary

Introduction

Vision is a crucial sense for the evolutionary success of many animal groups. Here we explore the diversity of visual pigments (opsins) in the transcriptomes of amphipods (Crustacea: Amphipoda) and conclude that it is restricted to middle (MWS) and long wavelength-sensitive (LWS) opsins in the overwhelming majority of examined species. Opsins form a monophyletic group within the G-coupled receptor superfamily and possess a characteristic conserved lysine residue in the seventh transmembrane domain (Lys7.43, or Lys296 in the bovine rhodopsin), to which retinal is attached via a protonated Schiff base [3]. They are further subdivided into four major groups (major eumetazoan opsin paralogs), one of which includes canonical visual ciliary (c) opsins and rhabdomeric (r) opsins [4]. At least four groups of animals (spiders; Pancrustacea, i.e. insects and crustaceans; cephalopods; and chordates) independently developed complex visual systems. Many insects and crustaceans possess compound eyes equipped with r-opsins [2, 4, 5]

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Conclusion