Microhabitat partitioning correlates with opsin gene expression in coral reef cardinalfishes (Apogonidae)

Fish are the most diverse vertebrate group, and they have evolved equally diverse visual systems, varying in terms of eye morphology, number and distribution of spectrally distinct photoreceptor types, visual opsin genes and opsin gene expression levels.
This variation is mainly due to adaptations driven by two factors: differences in the light environments and behavioural tasks. However, while the effects of large-scale habitat differences are well described, it is less clear whether visual systems also adapt to differences in environmental light at the microhabitat level.
To address this, we assessed the relationship between microhabitat use and visual system features in fishes inhabiting coral reefs, where habitat partitioning is particularly common.
We suggest that differences in microhabitat use by cardinalfishes (Apogonidae) drive morphological and molecular adaptations in their visual systems. To test this, we investigated diurnal microhabitat use in 17 cardinalfish spec...