Proteinsynthesekapazität und Wachstum bei Kammmuscheln (Pectiniden) und Fischen (Zoarciden) aus polaren und gemäßigten Breiten

Polar marine invertebrates and fish grow slowly. At present there are three basic explanations for this slow growth: 1. a direct limitation by temperature, 2. rising costs of maintenance at the expense of a reduction in growth, 3. seasonal resource limitation. On the cellular level the rate-limiting effect of temperature on growth could be excluded for the cold stenothermal scallop Adamussium colbecki and for the Antarctic eelpout Pachycara brachycephalum. The protein synthesis, measured in vitro, was cold compensated in these species compared to related eurythermal species, the European scallop Aequipecten opercularis and the North Sea eelpout Zoarces viviparus. Within the temperature tolerance of P. brachycephalum the cold adapted protein synthesis apparatus could still be acclimated to various temperatures. Compensated protein synthesis capacities in Antarctic scallops and eelpout have been achieved by low activation energies and high RNA translation capacities and indicate the development of a cost efficient growth apparatus. Unlike Antarctic fish, Antarctic invertebrates exhibit higher RNA contents when compared to related species from warmer waters. These over compensated protein synthesis capacities due to high RNA contents seem specific for Antarctic invertebrates and support high growth efficiencies during the austral summer. A comparison of in vivo and in vitro protein synthesis rates suggests that actual in vivo rates remain far below capacity. Therefore the regulation must occur on a higher level. A sensible regulation factor could be the pHi. Differing energy budgets and trade-offs between lifestyle, exercise and growth performance of cold stenothermal and eurythermal animals are discussed. A basic requirement is that the energetic costs for the protein synthesis are the same as demonstrated for both scallop species. Despite even low maintenance costs, cold stenothermal animals exhibit slow annual growth rates suggesting seasonal resource limitation.