Data from: Evolutionary history of chemosensory-related gene families across the Arthropoda

Chemosensory-related gene (CRG) families have been studied extensively in
insects, but their evolutionary history across the Arthropoda had remained
relatively unexplored. Here, we address current hypotheses and prior
conclusions on CRG family evolution using a more comprehensive data set.
In particular, odorant receptors were hypothesized to have proliferated
during terrestrial colonization by insects (hexapods), but their
association with other pancrustacean clades and with independent
terrestrial colonizations in other arthropod subphyla have been unclear.
We also examine hypotheses on which arthropod CRG family is most ancient.
Thus, we reconstructed phylogenies of CRGs, including those from new
arthropod genomes and transcriptomes, and mapped CRG gains and losses
across arthropod lineages. Our analysis was strengthened by including
crustaceans, especially copepods, which reside outside the
hexapod/branchiopod clade within the subphylum Pancrustacea. We generated
the first high-resolution genome sequence of the copepod Eurytemora
affinis and annotated its CRGs. We found odorant receptors and odorant
binding proteins present only in hexapods (insects) and absent from all
other arthropod lineages, indicating that they are not universal
adaptations to land. Gustatory receptors likely represent the oldest
chemosensory receptors among CRGs, dating back to the Placozoa. We also
clarified and confirmed the evolutionary history of antennal ionotropic
receptors across the Arthropoda. All antennal ionotropic receptors in E.
affinis were expressed more highly in males than in females, suggestive of
an association with male mate-recognition behavior. This study is the most
comprehensive comparative analysis to date of CRG family evolution across
the largest and most speciose metazoan phylum Arthropoda.