Widespread Occurrence of Fluorescent Morphological Lipofuscin in the Crustacean Brain

Abstract

An indication of the breadth of occurrence of fluorescent lipofuscin age-pigment in the brains of crustaceans was sought, following a recent demonstration of the potential of the fluorescent morphological pigment as an index of age in the commercial fresh-water crayfish Cherax quadricarinatus. The brains of adult individuals from 37 species, in a variety of crustacean orders, were examined. The presence of lipofuscin was assessed using fluorescence microscopy of histological sections and fixed- or fresh-brain squashes. The occurrence of resolvable fluorescent lipofuscin granules was a taxonomically widespread, but not universal phenomenon. Although the fluorescent material was generally more conspicuous in larger animals, its occurrence was not rigidly correlated with either adult body size or estimated chronological age over the range of species examined. Possible explanations for the observed variations are discussed along with implications for the potential use of the pigment as an index of age in the Crustacea.