Robust sensory traits across light habitats: Visual signals but not
receptors vary in centrarchids inhabiting distinct photic environments
Abstract
Visual communication in fish is often shaped by the light environment
they inhabit, which influences both sensory (e.g., eye size, opsin gene
expression) and signaling traits (e.g., body reflectance). This study
explores the phenotypic variation in the visual communication traits of
six species of centrarchids (Centrarchidae) inhabiting two contrasting
light environments. We measured morphological, molecular, and signaling
traits to determine their variation across photic conditions. Our
findings reveal significant interspecific variation in sensory traits
but no consistent phenotypic variation between light environments.
Centrarchids showed robust visual systems with red-green dichromatic
vision, which was largely unaffected by different light habitats. We
also found significant molecular evolution in the visual opsin genes,
although these changes were not associated with environmental
conditions. However, body reflectance displayed species-specific
responses to environmental conditions, suggesting that signaling traits
may be more flexible than sensory traits. Overall, our results challenge
the generality of the current paradigm in visual ecology, which portrays
visual systems in fish as highly tunable owing to photic conditions. Our
study highlights the potential evolutionary or developmental constraints
on centrarchid visual systems and their implications for adaptability to
various habitats and novel environmental threats.