Regulation of red fluorescent light emission in a cryptic marine fish

TLDR: This is the first time chromatophore units are found to control fluorescent emission in marine teleost fishes and the discovery of a second mechanism for fluorescence modulation strengthens the view that fluorescence is a relevant and adaptive component of fish colouration.

Abstract: Introduction Animal colouration is a trade-off between being seen by intended, intra- or inter-specific receivers while not being seen by the unintended. Many fishes solve this problem by adaptive colouration. Here, we investigate whether this also holds for fluorescent pigments. In those aquatic environments in which the ambient light is dominated by bluish light, red fluorescence can generate high-contrast signals. The marine, cryptic fish Tripterygion delaisi inhabits such environments and has a bright red-fluorescent iris that can be rapidly up- and down-regulated. Here, we described the physiological and cellular mechanism of this phenomenon using a neurostimulation treatment with KCl and histology.