Abstracts

The meso- and bathypelagic zones (200 – 4000 m depth) harbor the highest biodiversity of bioluminescent organisms on the Earth. The main light sources in these depths are downwelling sunlight and bioluminescence, both characterized by dim, narrow blue-green spectra. Stomiidae (Stomiiformes) is the most diverse family of bioluminescent deep-sea fishes. Stomiids bear serial body photophores that produce blue-green light for counterillumination, and sub-ocular photophores that emit red light for illumination and intra-specific communication. Red fluorescing pigments are present in both photophore types.Fluorescent proteins were extracted from the body photophores of Stomias affinis and sub-orbital photophore of Malacosteus australis. Proteins were purified by ion exchange and gel filtration chromatography. Red fluorescent fractions were run on SDS-PAGE electrophoresis gel, and respective bands were excised for nLC-MS mass spectrometry. Peptide sequences obtained from nLC-MS were tracked on transcriptomes of respective photophore types and genera. Chromophores were also analyzed using HPLC. Spectral properties of light transmission and fluorescence of the proteins were obtained by spectrophotometry.Two potential novel red fluorescent proteins were found for each photophore type of Stomiidae. The preliminary results suggest the two proteins diverge in peptide sequences, chromophores, physicochemical and spectral characteristics. Body photophores of Stomiidae evolved a lilac protein for spectral cutoff on counterillumination. Sub-orbital photophores arose exclusively in Malacosteinae using a red fluorescent protein to emit red light for illumination. Stomiids evolved two fluorescent proteins in distinct photophore mechanisms for particular ecological purposes, reflecting the benefits and complexity of bioluminescence in the evolution of these deep-sea fishes.