Fig. 4.

Phylogenetic relationship of opsins and animal phototransduction cascades. The unrooted tree of the opsin family was inferred based on Fig. S2A. The amino acid sequences of opsins that were revealed to function as photopigments and their apparent homologues were included. The cnidarian lineage is highlighted (red). The G protein subtypes that the opsins are coupled with and the second messengers in the phototransduction cascades, as well as the photoreceptor cell types, are indicated.