Effects of acclimation temperature on the growth of Perna viridis (Bivalvia : Mytilidae), using the RNA/DNA ratio

Temperature affects growth rate in aquatic organisms. This can be evaluated in short term using bio chemical indexes (RNA/DNA and Protein/DNA). The ef fect of acclimatization temperature on the instantaneous growth and physiol ogical condition of Perna viridis was studied in organisms collected in La Esmeralda, Sucre State (Venezuela) and taken to the laboratory, where group s of 100 organisms (size 3.0 - 3.5 cm, anteroposterior measurement) were ac climatized at 15, 20, 26 or 28 degreesC during four weeks. later they were kept in a 60 liters aquarium for another six weeks under the same condition s. Each week, ten organisms per group were extracted to measure concentrati ons of RNA, DNA (by a fluorometric method with ethidium bromide) and protei ns (by a colorimetric method), in tissues (digestive gland, adductor muscle and gills). Protein concentration was greater and highly significant at 15 degreesC for all studied tissues. The opposite was obtained with the RNA/D NA and Protein/DNA ratios: the greatest increase was observed at the highes t temperature (28 degreesC) for all tissues. At the lowest temperature ther e was a tendency to reduce both indexes with time. Greater instantaneous gr owth can be expected at higher temperatures and 28 degreesC was optimal for growth in these specimens.