Analysis of opsin variation and expression in cave and surface populations of Gammarus minus

Gammarus minus is a freshwater amphipod crustacean found in both cave and spring ecosystems. The cave populations have reduced eyes, longer antennae, larger body size and reduced pigmentation relative to the spring populations. In this study, I analyzed the opsin gene sequence from 60 cave and 99 spring individuals for determining the opsin gene sequence variation between the cave and spring populations. I also studied the difference in opsin expression between the two populations. My analysis revealed that there is no significant difference in opsin gene variation between the two populations. I also failed to detect any evidence of neutral evolution of opsin within the cave populations. However, there was significant difference in opsin expression between the cave and spring populations. These data suggest that opsin in the cave G. minus is required for survival and could probably be playing a role unrelated to vision.