Difference Between Rhodopsin And Sea Lampreys

The second metamorphosis occurs at the end of the juvenile stage. When the sea lamprey are ready to travel back upstream, their eye pigment changes from rhodopsin to porphyropsin. The main difference between the two is that porphyropsin is typically found in freshwater vertebrates, versus the rhodopsin in the marine and land vertebrates. Prior to the metamorphosis, the sex of the lamprey is very had to differentiate as well, but after this second metamorphosis, the lamprey is now a sexually mature adult and one is able to tell the male from the female. The sea lamprey now migrates back upstream to spawn (Wald 1957). The sea lamprey uses pheromones, natural chemicals, released by other sea lampreys in their larval stage, to locate certain
streams and tributaries to spawn in. Tens of thousands of eggs are laid by the female lamprey, and after these are laid and fertilized, both the male and female lamprey die (New York State Department of Environmental Conservation 2015).