THERMAL COMPENSATION IN PROTEIN AND RNA SYNTHESIS DURING THE INTERMOLT CYCLE OF THE AMERICAN LOBSTER,HOMARUS AMERICANUS

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Abstract
The effect of the intermolt cycle condition upon the capacity of lobsters to acclimate to an altered thermal regime was examined. The in vitro rates of incorporation of labeled precursors into protein and into RNA by both the salvage and de novo pyrimidine pathways were measured in tissues of intermolt and premolt lobsters acclimated to 5.degree. and 20.degree. C. Incorporation of 3H-leucine into protein and 3H-uridine into RNA (pyrimidine salvage pathway) in intermolt tissue responded to temperature acclimation by a compensatory translation of the rate vs. temperature curve, while premolt tissue exhibited either no change or an inverse compensation. The existence of the complete de novo pathway for pyrimidine biosynthesis was demonstrated in Crustacea. The response of this pathway to an altered thermal regime was independent of the molt cycle condition. RNA levels and the rate of incorporation of pyrimidines into RNA by both salvage and de novo pathways increased in the premolt hepatopancreas.