Ocular and extraocular expression of opsins reveals evolutionary trends underlying visual and non-visual functions in bivalves (Pteriomorphia)

Opsin proteins are central to photoreception and have diversified extensively to support both visual and nonvisual functions in animals. While the molecular conservation is striking, the evolutionary pathways that shaped opsin diversity, particularly in relation to visual and extraocular roles, remain poorly understood. To address this gap, we examined opsin repertoires in Pteriomorphia, a diverse group of mostly sessile marine bivalves with multiple photoreceptor systems and ecologies. We generated transcriptomes for 12 species, including eyed and eyeless adults, and analyzed published RNA-seq data from five additional species, covering all taxonomic orders and eye types. We identified and classified opsins expressed in the photosensitive mantle margin and eyes using phylogenetically informed annotation. We tested whether opsin diversity is associated with eye presence or mobility and determined which opsins are widely used. Our results suggest that bivalve eyes generally express more ..., We compare 17 species based on transcriptomic data to determine opsin profiles from photosensitive tissues, including eyes from eyed species and mantle margin (extraocular tissue) from eyeless species. Individuals of 12 species were collected, dissected, preserved, and immediately stored at -80 ºC. In addition, five other pteriomorphian species with publicly available RNA-seq data from either the mantle margin or the eyes were included. Raw reads were downloaded, and transcriptomes were generated. All five Pteriomorphia orders were sampled, totaling 17 species from 10 families. Our dataset also covers the five eye types, i.e., pigmented cup, cap eyespot, invaginated eye, compound eye, and mirror eye, occurring in the group.
Total RNA was extracted from dissected mantle margins and eye samples. All libraries were prepared and sequenced (300 cycles) on an Illumina NovaSeq 6000. Details on quality checking, de novo assembly, protein prediction, and other relevant information are listed in ..., , # Ocular and extraocular expression of opsins reveals evolutionary trends underlying visual and non-visual functions in bivalves (Pteriomorphia)

Dataset DOI: [10.5061/dryad.kd51c5bhj](https://doi.org/10.5061/dryad.kd51c5bhj)

## Description of the data and file structure

We compare 17 species based on transcriptomic data to determine opsin profiles from photosensitive tissues, including eyes from eyed species and mantle margin (extraocular tissue) from eyeless species. We generated transcriptomes for 12 species, including eyed and eyeless adults, and analyzed published RNA-seq data from five additional species, covering all taxonomic orders and eye types. We identified and classified opsins expressed in the photosensitive mantle margin and eyes using phylogenetically informed annotation. We tested whether opsin diversity is associated with eye presence, photoreception class, or mobility, and determined which opsins are widely used.

### Files and variables

#### File: species_tree.fas..., ,