Phylogenetic and transcriptomic analyses reveal the evolution of bioluminescence and light detection in marine deep-sea shrimps of the family Oplophoridae (Crustacea: Decapoda)

Abstract

Bioluminescence is essential to the survival of many organisms, particularly in the deep sea where light is limited. Shrimp of the family Oplophoridae exhibit a remarkable mechanism of bioluminescence in the form of a secretion used for predatory defense. Three of the ten genera possess an additional mode of bioluminescence in the form of light-emitting organs called photophores. Phylogenetic analyses can be useful for tracing the evolution of bioluminescence, however, the few studies that have attempted to reconcile the relationships within Oplophoridae have generated trees with low-resolution. We present the most comprehensive phylogeny of Oplophoridae to date, with 90% genera coverage using seven genes (mitochondrial and nuclear) across 30 oplophorid species. We use our resulting topology to trace the evolution of bioluminescence within Oplophoridae. Previous studies have suggested that oplophorid visual systems may be tuned to differentiate the separate modes of bioluminescence. While all oplophorid shrimp possess a visual pigment sensitive to blue-green light, only those bearing photophores have an additional pigment sensitive to near-ultraviolet light. We attempt to characterize opsins, visual pigment proteins essential to light detection, in two photophore-bearing species (Systellaspis debilis and Oplophorus gracilirostris) and make inferences regarding their function and evolutionary significance.

Keywords: Bioluminescence; Opsins; Photophores; RNA-seq; Shrimp; Ultraviolet.