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Table 1 Tetrapoda opsins and their functions. Subfamilies characterization according to [5, 12, 78] and [4]

From: Adaptive genomic evolution of opsins reveals that early mammals flourished in nocturnal environments

Subfamily Opsins Functions
Visual opsins RH1
RH2
OPN1sw1
OPN1sw2
OPN1lw
Rhodopsin mediates vision in dim-light whereas conopsins are responsible for colour vision. OPN1lw is sensitive to red-green or long-wavelengths, RH2 to green or middle wavelengths and two short-wave conopsins (OPN1sw2 and OPN1sw1) respond to blue-violet or violet-ultraviolet wavelengths, respectively.
Non-visual opsins (sensu stricto) OPN3
TMT
TMT2
TMT (teleost-multiple-tissue) are expressed in the liver, kidney and heart as well as eye and brain. Phylogenetic analysis reveals that it clades with OPN3, which also exhibits a multiple patterns of tissue expression.
Pineal opsins PARA
PARIE
PIN
VA
Multiple opsins (PARA, PARIE, PIN) have been isolated from the parapineal complex. VA opsin is also expressed in the retina and was shown that forms a functional photopigment sensitive in the 460–480 nm range.
Photoisomerases and Neuropsins OPN5
RGR
RRH
RGR and RRH have a probable role as all-trans retinal photoisomerases. OPN5 shows an absorption maximum at 380 nm and is thus UV-sensitive.
Melanopsins OPN4x
OPN4m
Melanopsins are involved in circadian rhythm regulation and pupillary light reflexes.