Individual age and connective tissue lipofuscin in the hard clam Eurhomalea exalbida

In the hard clam Eurhomalea exalbida, autofluorescent granules were detected in high concentrations in the connective tissue around the intestine and in other tissues. Autofluorescence combined with Sudan black B and PAS positive reactions suggested that these granules were lipofuscin-like. The concentration of this material in the connective tissue (CT) around the intestine was quantified by image analysis and expressed as total area fraction occupied by lipofuscin granules. Lipofuscin concentration was distinctly better related with individual age as determined from stable isotope-validated shell growth bands than with any morphometric parameter. This relationship was described best by a Gompertz model: Lipofuscint = 24.79e e 0.029(Age t 58.578) (N= 38; rnl 2 = 0.882). Age was predicted from lipofuscinCT concentration by a von Bertalanffy model: Age t = 68.00 (1 e 0.146(Lipofuscint + ) (N = 38; rnl 2 = 0.933). Our findings suggest that lipofuscinCT concentration in E. exalbida is a function of individual age. If this holds true for bivalves in general, lipofuscin may be a suitable proxy for age in species with less clear shell growth band patterns. D 2002 Elsevier Science B.V. All rights reserved.