The deep sea is home to fish species that can detect various wavelengths of light in near-total darkness. Unlike other vertebrates, they have several genes for the light-sensitive photopigment rhodopsin, which likely enables these fish to detect bioluminescent signals from light-emitting organs. The findings were published in the journal Science by an international team of researchers led by evolutionary biologists from the University of Basel.
Color vision in vertebrates is usually achieved through the interaction of various photopigments in the cone cells found in the retina. Each of these photopigments reacts to a certain wavelength of light. In humans, for example, these wavelengths are the red, green and blue range of the light spectrum. Color vision is only possible in daylight, however. In darkness, vertebrates detect the few available light particles with their light-sensitive rod cells, which contain only a single type of the photopigment rhodopsin – explaining why nearly all vertebrates are color-blind at night.
A genetic record for the silver spinyfin
An international team of researchers lead by Professor Walter Salzburger from the University of Basel recently analyzed more than 100 fish genomes, including those of fish living in deep-sea habitats. The zoologists discovered that certain deep-sea fish have expanded their repertoire of rhodopsin genes. In the case of the silver spinyfin (Diretmus argenteus), they found no less than 38 copies of the rhodopsin gene, in addition to two other opsins of a different type. “This makes the darkness-dwelling silver spinyfin the vertebrate with the most photopigment genes by far,” explains Salzburger.
Read more at University of Basel