RESUMO
Peracarid crustaceans are among the most important taxa in terms of biodiversity and carbon-flow within the Weddell Sea benthos; however, very few data on their age, growth and productivity are available. This study uses the pigment lipofuscin as an age marker in the scavenging amphipod Waldeckia obesa (Chevreux, 1905) from the eastern Weddell Sea. Resin brain sections of 159 trap-caught specimens (1.2 to 7.7 mm coxal plate length L(cox) equal to 5 to 31 mm total length) were recorded digitally by confocal microscopy, and images were analysed. A modal progression analysis of the lipofuscin concentration-frequency distribution revealed five regularly spaced modes presumed to reflect consecutive annual age classes. Single females outside the range of mode V occurred, indicating maximum age of up to 8 years in females. No regular modes were obvious from the comparable length-frequency distribution of 386 individuals. Average yearly pigment accumulation was linear, and accumulation rates did not differ between sexes. The estimates of the growth parameters L(infinity) and k of the von Bertalanffy growth function were 7.47 mm L(cox) and 0.50 per year in females, respectively, and 6.92 mm L(cox) and 0.60 per year in males, respectively. Mortality, estimated from catch curves, amounted to 0.27 per year in females and 0.43 per year in males. P/B ratio, calculated from the mass specific growth rate method, was 0.38 per year for the pooled population (0.25 per year in females, 0.31 per year in males, 2.26 per year in juveniles). The results are discussed with regard to advantages and drawbacks of the methodology, and are compared with results from warmer water habitats.
