The recently characterized opsin group of xenopsins is likely a major player in animal eye evolution and may have been present in an ancient, highly plastic eye photoreceptor cell type.

A new member of the family of light-sensitive proteins called opsins has stirred up our view of photoreceptors.

The employment of xenopsin in ciliary and mixed microvillar/ciliary eye sensory cells in several protostome animals suggests high evolutionary plasticity of photoreceptors.