Changes in expression levels of opsins at different life stages of the eel. A. The expression level of rh2 and sws2 cone opsin transcripts as copy numbers per 50 ng total RNA. The level of green opsin is approximately equivalent in the different life stages, but the amount of blue opsin doubles between the glass and silver stage. B. The expression of the two rod (rh1) opsin transcripts as copy numbers per 50 ng total RNA. The level of fwo transcript appears to increase slightly between the glass and later stages, but the amount of dso transcript increases markedly between the glass and silver life stages. Error bars show standard deviations which are necessarily large for the non-glass eels as each sample represents a point on a continuum.