In vitro protein synthesis capacities in a cold stenothermal and a temperate eurythermal pectinid.

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 microg protein mg FW(-1) day(-1)) and the translational capacities of RNA (k(RNA in vitro) mg protein mg RNA(-1) day(-1)). In vitro protein synthesis capacity in the cold-adapted pectinid at 0 degrees C was similar to the one found in the temperate scallop at 25 degrees C. These findings might reflect cold compensated rates in Adamussium 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 E(a) and Q(10) in Adamussium colbecki in the temperature range 0-15 degrees C. Reduced protein synthesis and translational capacities were found in vitro in gills of long-term aquarium-maintained Adamussium 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 synthesized per milligram of RNA (RNA translational capacity, k(RNA in vitro)). Such changes may involve food uptake or mirror metabolic depression strategies, like those occurring 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.