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Use of estimates of ribonucleic acid to predict the growth rates of zooplanktonic organisms. Pease, Alan Kingsley

Abstract

The concentration of RNA (Schneider procedure, 1945) and the dry weight of the developing stages of the brine shrimp Artemia salina were measured during the first 63 days of growth of the organism in the laboratory; RNA and the dry weight of starved stage V Calanus plumchrus were followed for 20 days. The same techniques were applied to the developmental stages of several species of zooplankton obtained during the course of one year from Saanich Inlet, Vancouver Island, B.C. The data collected from the laboratory and the field were used to test the validity of the RNA/Growth relationship proposed by Sutcliffe (1965) as a means to predict the rate of increase in dry weight (growth rate) of such organisms. Errors in the estimation of RNA occured. These resulted from chromogenic materials other than the pentose sugars ribose and desoxyribose being present in the hot PCA extracts of zooplanktonic organisms. Detection of the interfering chromogens was possible by examining the absorption spectra of the hot PCA extracts treated with orcinol between the wave-lengths 550 to 700 mμ. An attempt has been made to minimize such errors by calculating the amount of RNA from the difference in absorbance recorded at 670 mμ minus that at 615 mμ. Correlation of growth predicted from RNA values and the observed increase in dry weight of the organisms was greatest during their most rapid period of development. During other periods of development, RNA values were generally in excess of requirements for the observed increase in dry weight and may represent metabolic processes other than those associated with this increase.

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