Fig. 4From: Insights into the evolutionary origin of the pineal color discrimination mechanism from the river lampreyThe proposed evolutionary model for color opponency systems in vertebrate pineal-related organs. Bold lines indicate branches of the vertebrate lineage. Speculated ancestral photoreceptor cell types and current types for the pineal color discrimination are drawn on each key node. Please see the “Discussion” section for the detailed descriptions of points (i)–(v)Back to article page