Quantitative comparison of in situ lipofuscin concentration with soluble autofluorescence intensity in the crustacean brain.

The intensity of soluble 'lipofuscin-like' autofluorescences extracted from the brain of the freshwater crayfish, Cherax quadricarinatus, was compared with the concentration of morphological lipofuscin present in sections of the same tissue. This study represents the first quantitative demonstration that these soluble autofluorescences, previously attributable to lipofuscin or fluorescent age pigment (FAP), actually bear no quantitative relationship to it at all. This result confirms previous suspicions in the literature. In some cases the intensities of these unidentified soluble autofluorescences are positive linear or curvilinear functions of organ or body weight and, therefore, may give the misleading impression that they are related to age and derived from age pigment. It is strongly recommended that researchers, particularly on aquatic species, avoid using the original biochemical assay procedure for lipofuscin and its more recent modifications.