The autofluorescent age pigment lipofuscin: key to age, growth and productivity of the Antarctic amphipod Waldeckia obesa (Chevreux, 1905)

Peracarid crustaceans are among the most important taxa in terms of biodive rsity and carbon-flow within the Weddell Sea benthos; however, very few dat a on their age, growth and productivity are available. This study uses the pigment lipofuscin as on age marker in the scavenging amphipod Waldeckia ob esa (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, an d images were analysed. A modal progression analysis of the lipofuscin conc entration-frequency distribution revealed five regularly spaced modes presu med to reflect consecutive annual age classes. Single females outside the r ange of mode V occurred, indicating maximum age of up to 8 years in females . No regular modes were obvious from the comparable length-frequency distri bution of 386 individuals. Average yearly pigment accumulation was linear, and accumulation rates did not differ between sexes. The estimates of the g rowth parameters L-infinity and k of the von Bertalanffy growth function we re 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 cat ch 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 rega rd to advantages and drawbacks of the methodology, and are compared with re sults from wanner water habitats. (C) 2001 Elsevier Science B.V. All rights reserved.