Crustacean conundrums: a review of opsin diversity and evolution

Abstract

Knowledge of crustacean vision is lacking compared to the more well-studied vertebrates and insects. While crustacean visual systems are typically conserved morphologically, the molecular components (i.e. opsins) remain understudied. This review aims to characterize opsin diversity across crustacean lineages for an integrated view of visual system evolution. Using publicly available data from 95 species, we identified opsin sequences and classified them by clade. Our analysis produced 485 putative visual opsins and 141 non-visual opsins. The visual opsins were separated into six clades: long wavelength sensitive (LWS), middle wavelength sensitive (MWS) 1 and 2, short wavelength or ultraviolet sensitive (SWS/UVS) and a clade of thecostracan opsins, with multiple LWS and MWS opsin copies observed. The SWS/UVS opsins were relatively conserved in most species. The crustacean classes Cephalocarida, Remipedia and Hexanauplia exhibited reduced visual opsin diversity compared to others, with the malacostracan decapods having the highest opsin diversity. Non-visual opsins were identified from all investigated classes except Cephalocarida. Additionally, a novel clade of non-visual crustacean-specific, R-type opsins (Rc) was discovered. This review aims to provide a framework for future research on crustacean vision, with an emphasis on the need for more work in spectral characterization and molecular analysis. This article is part of the theme issue ‘Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods’.

Ecological genomics in the Northern krill uncovers loci for local adaptation across ocean basins

“…Moreover, we detected expansions of the opsin gene repertoire, which encodes the light-sensitive receptors in ommatidia. Fourteen opsins have previously been identified from RNA in the Antarctic krill E. superba (34), which are thought to enable vision under the divergent light conditions experienced throughout its life cycle and vertical migrations (35), while 16 opsins have recently been inferred from M. norvegica RNA (36). We queried our M. norvegica gene-set and the KrillDB 2 E. superba RNA database against the curated crustacean opsin dataset in ref 35.…”

Comparative population genomics provide new insight into the evolutionary history and adaptive potential of World Ocean krill

“…S9B), automatically annotated as Rh5. However, queries against KrillDB 2 (Urso et al 2022) and NCBI Genbank suggest it is a peropsin, a light-sensitive yet non-visual receptor with poorly understood function in crustaceans but with expression patterns that oscillate daily in Antarctic krill (Henze and Oakley 2015;Biscontin et al 2016;Palecanda et al 2022).…”

“…M. norvegica). This includes efforts to uncover and functionally characterize the photoreceptor and circadian clock gene repertoires (Biscontin et al 2016;Christie et al 2017;Palecanda et al 2022;Urso et al 2022) or genes involved in regulating the molting cycle (Seear et al 2010), seasonal dynamics (Seear et al 2012;Höring et al 2021) and heat shock response (Huenerlage et al 2016;Papot et al 2016). However, analyses of how specific genes may contribute to environmental adaptation through natural selection have only been performed in heat shock proteins hsp70 genes of Antarctic species before.…”

High diversity of arthropod colour vision: from genes to ecology

“…Among Chelicerata, opsins diversity of horseshoe crabs [27] and some spiders [29] have been studied. Pancrustaceans have been covered well by Henze & Oakley [25], but Palecanda et al [19] present the most comprehensive study on opsins in crustaceans to date and report some clades to have only one or two visual opsins (r-opsins) while others have multiple gene duplications specifically of LWS and MWS opsins. A detailed report on the best studied and likely most diverse clade among crustaceans, the stomatopods, is presented by Cronin et al [20].…”

“…[16][17][18]) and crustaceans (e.g. [19,20]). This special issue aims to present the current state of knowledge on arthropod colour vision by combining reviews, new research articles and a methods paper reporting a novel tool for generating colour stimuli.…”