Spectral sensitivity in ray-finned fishes: diversity, ecology, and shared descent

Abstract

A major goal of sensory ecology is to identify factors that underlie sensory-trait variation. One open question centers on why fishes show the greatest diversity among vertebrates in their capacity to detect color (i.e. spectral sensitivity). Over the past several decades, λ max values (photoreceptor class peak sensitivity) and chromacy (photoreceptor class number) have been cataloged for hundreds of fish species, yet the ecological basis of this diversity and the functional significance of high chromacy levels (e.g. tetra-and pentachromacy) remain unclear. In this study, we examined phylogenetic, physiological and ecological patterns of spectral sensitivity of ray-finned fishes (Actinoptergyii) via a meta-analysis of data compiled from 213 species. Across the fishes sampled, our results indicate that trichromacy is most common, ultraviolet λ max values are not found in monochromatic or dichromatic species, and increasing chromacy, including from tetra-to pentachromacy, significantly increases spectral sensitivity range. In an ecological analysis, multivariate phylogenetic latent liability modeling was performed to analyze correlations between chromacy and five hypothesized predictors (depth, habitat, diet, body coloration, body size). In a model not accounting for phylogenetic relatedness, each predictor with the exception of habitat significantly correlated with chromacy: a positive relationship in body color and negative relationships with body size, diet and depth. However, after phylogenetic correction, the only remaining correlated predictor was depth. The findings of this study indicate that phyletic heritage and depth are important factors in fish spectral sensitivity and impart caution about excluding phylogenetic comparative methods in studies of sensory trait variation.

Light environment drives evolution of color vision genes in butterflies and moths

“…Resource allocation trade-offs can cause a loss of stabilizing selection on genes of inefficient sensory systems, resulting in their downregulation or them becoming pseudogenes. This has been seen in nocturnal mammals 21 , cave-dwelling crayfish 22 , and deep-sea organisms [23][24][25] . If diminished light availability causes reduced opsin expression and loss, abundant light, conversely, may cause higher opsin expression, or prevent the loss of duplicated opsins and eventually lead to functional divergence.…”

Seeing the rainbow: mechanisms underlying spectral sensitivity in teleost fishes

“…The peak spectral sensitivities of fish visual pigments have been quantified physiologically for more than 50 years; first through pigment extraction and then using microspectrophotometry of individual photoreceptors (Dartnall and Lythgoe, 1965;Levine and MacNichol, 1979;Loew and Lythgoe, 1978;Munz, 1958;reviewed in Bowmaker 1995;Schweikert et al, 2019Schweikert et al, , 2018. This work demonstrated the diverse sensitivities of rods and cones based on a diverse set of opsin genes.…”

A five‐channel LED display to investigate UV perception

“…The pixels have a 5.3 mm centre‐to‐centre spacing and each contains five LEDs ranging from 367 to 629 nm (Figure 1). The specific LEDs were chosen for their coverage of spectral ranges relevant to various animals, including many teleost fishes, birds, insects and some reptiles (reviewed in Briscoe & Chittka, 2001; Hart & Vorobyev, 2005; Schweikert et al., 2018). To promote uniform colour mixing, a diffuser (0.5 mm PTFE sheet) is mounted 1 cm from the LEDs with a baffle to prevent mixing between pixels (Figure 2).…”