Protein Synthesis and Oxygen Consumption of the Shore Crab Carcinus maenas after a Meal

The oxygen consumption of the crab Carcinus fed a single meal of Mytilus tissue equivalent to 2.6% of the crabs' fresh weight increased 2.3-fold at 3 h after the meal and returned to its previous value within 24 h. The whole-body protein synthesis rates of animals fed meals of similar size paralleled the oxygen consumption changes; protein synthesis rates increased twofold by 3 h after the meal and remained elevated for 16h. Estimates of the minimal costs of protein synthesis indicated that they accounted for between 20% and 37% of the measured oxygen consumption. There was a linear correlation between protein synthesis rates and oxygen consumption rates. The protein synthesis rates of the midgut gland, gill, heart, proventriculus, leg extensor muscle, and claw muscle all increased by 3 h after a meal, but only in the claw muscle was this stimulation in protein synthesis prolonged. These initial increases in protein synthesis were not accompanied by any significant change in RNA:protein ratios in any of the tissues; only at 9 h after the meal had the RNA concentration approached the values found in continuously fed animals. We concluded that a single meal initiated a surge of protein synthesis in the tissues of Carcinus that was closely correlated with total oxygen consumption and that occurred initially through an increase in RNA activity.