Lipofuscin as an indicator of age in crustaceans: Analysis of the pigment in the American lobster Homarus americanus

Lipofuscin content was determined in the brains of 41 American lobsters Homarus americanus (Milne-Edwards) aged 4, 13 and 27 mo reared individually at 19 to 20 degrees C. Lipofuscin was quantified by fluorescence microscopy and image analysis. Lipofuscin granules occurred in each age group and in the oldest group appeared as large aggregations collectively averaging 2.1% of the area of histological sections of the olfactory lobe cell mass. Carapace length-corrected lipofuscin area % gave the highest correlation with age (r = 0.99, p < 0.0001) and a non-linear best fit regression (y = 0.00264 x Age(2.03)). The size and number of lipofuscin granules and carapace length were also significantly related to age. Lipofuscin concentration was not significantly correlated with carapace length within any of the 3 age classes (4 mo: r = -0.078, 13 mo: r = -0.20, 27 mo: r = -0.351). These results suggest the possibility that the lipofuscin technique can differentiate cohorts in natural populations. However, environmental temperature and the possibility of other factors affecting metabolic rate may need to be taken into account when attempting to apply the laboratory model to wild populations.