Bioluminescence and environmental light drive the visual evolution of deep-sea shrimp (Oplophoroidea)

Light functions as the universal language in the deep sea (> 200
m). Both bioluminescent emissions and downwelling light sources dimly
illuminate the water column and can drive sensory system evolution. In
pelagic environments, vertically migrating animals can experience drastic
changes to their lighting environment across depth, subjecting them to
unique selective pressures, possibly to distinguish between changes in
ambient light and bioluminescent sources. Here we show that visual opsin
diversity across a group of variable vertical migrators- bioluminescent
deep-sea shrimp belonging to the Superfamily Oplophoroidea- is higher
among species who migrate to shallower waters with more variable light
conditions. Further, we provide evidence for adaptive visual evolution
among species who have evolved an additional mode of bioluminescence
(photophores), including positive selection for a putative mid-wavelength
sensitive opsin that may facilitate light source discrimination.
Diversification of this opsin appears to play an important role in the
visual ecologies of photophore-bearing shrimp with its diversification in
Oplophoroidea likely playing a critical role in the fitness and
evolutionary success of this group.