The translational system was isolated from the gills of the Antarctic scallop Adamussium colbecki (Smith) and the European scallop Aequipecten opercularis (Linnaeus) for in vitro protein synthesis capacities (µg protein mg FW-1 day-1) and the translational capacities of RNA (kRNA in vitro mg protein per mg RNA per day). In vitro protein synthesis capacity in the cold adapted pectinid at 0°C was similar to the one found in the temperate scallop at 25°C. These findings might reflect cold compensated rates in A. colbecki, partly explainable by high tissue levels of RNA. Cold compensated in vitro protein synthesis capacities may further result from increments in the translational capacity of RNA. The thermal sensitivity of the translation machinery was slightly different in the two species, with significantly lower levels of Arrhenius activation energies Ea and Q10 in A. colbecki in the temperature range 0-15°C. Reduced protein synthesis and translational capacities were found in vitro in gills of long term aquarium maintained A. colbecki and were accounted for by a loss of protein synthesis machinery, i.e. a reduction in RNA levels, as well as a decrease in the amount of protein synthesised per mg of RNA (RNA translational capacity, kRNA in vitro). Such changes may involve food uptake or mirror metabolic depression strategies as during winter. Consequences of high in vitro RNA translational capacities found in the permanently cold adapted species are discussed in the context of seasonal food availability and growth rates at high latitudes.