NILE RED AS A PROBE FOR LIPID-STORAGE PRODUCTS IN BENTHIC COPEPODS

Nile red (NR) is a hydrophobic fluorophore that binds specifically to neutral lipids. We examined the usefulness of NR as a probe for detecting neutral-lipid-storage products in benthic (harpacticoid) copepods. Following a brief (30 min) exposure to NR, lipid droplets, which fluoresce a bright yellow/orange, were clearly visible under epifluorescent illumination. Analysis of fluorescent images was used to determine relative lipid concentrations. The NR procedure was used on copepods subjected to a range of starvation periods. As predicted, detectable lipid reserves decreased with increased starvation period. The sensitivity of the NR procedure makes it a potentially useful tool for comparing relative lipid levels in individual organisms, even where lipid concentrations are near or below the detection limits of conventional analytical methods.