Development and application of biochemical approaches for understanding age and growth in crustaceans

For crustaceans, information on the demographic structure of field population is typically based on size since they lack the permanent hard structures that are used for age estimation in vertebrates. This dissertation investigated the potential for by-products of cellular oxidation to provide a more quantitative measure of chronological and/or physiological age using the blue crab Callinectes sapidus as a model organism.; Chemical characterization of peroxidation products collectively called lipofuscin extracted from crab neural tissue found it to be dominated by three hydrophilic components of relatively low (<5 kDa) molecular weight. Only one major component is correlated with age which is very nitrogen rich and composed of 14 amino acids with dominance of leucine and isoleucine. Fluorescence properties showed a maximum emission fluorescence of 405–410 nm with a maximum excitation of 340–350 nm.; To understand growth and lipofuscin accumulation rates of blue crabs under natural conditions, juveniles were reared in outdoor ponds for more than one year period. Growth rates during summer and fall exceeded those reported in the literature. Despite growth rates that varied strongly with season, lipofuscin accumulation rate was constant and linear throughout the year. Lipofuscin levels in laboratory and pond-reared crabs were significantly correlated to size, but were more strongly correlated with chronological age. Lipofuscin accumulation rates for pond-reared crabs were similar to those estimated for laboratory-reared crabs, despite very different growth rates and patterns. Field-collected blue crabs contained highly variable levels of lipofuscin with no significant differences between genders. The potential importance of trace metal exposure as an enhancer of lipofuscin accumulation was investigated and found to be insignificant.; Modal analysis of normalized-lipofuscin in field-collected animals provided evidence of multiple demographic modes, whereas carapace width showed only two modes. Lipofuscin levels of age classes identified from lipofuscin-based modal analysis were within the range predicted by the accumulation rate established from known-age reared animals. Moreover, age structures based upon lipofuscin showed more realistic age distribution with expected recruitment patterns to the exploited stock as the blue crab. Therefore, the accumulation of peroxidation products (lipofuscin) would offer a significantly better approach for estimation of age in blue crabs than size alone.