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 lobster s Homarus americanus (Milne-Edwards) aged 4, 13 and 27 mo reared indiv idually at 19 to 20 degrees C. Lipofuscin was quantified by fluorescen ce microscopy and image analysis. Lipofuscin granules occurred in each age group and in the oldest group appeared as large aggregations coll ectively averaging 2.1% of the area of histological sections of the ol factory lobe cell mass. Carapace length-corrected lipofuscin area % ga ve the highest correlation with age (r = 0.99, p < 0.0001) and a non-l inear best fit regression (y = 0.00264 x Age(2.03)). The size and numb er of lipofuscin granules and carapace length were also significantly related to age. Lipofuscin concentration was not significantly correla ted 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 possi bility of other factors affecting metabolic rate may need to be taken into account when attempting to apply the laboratory model to wild pop ulations.