Nematode speci c gravity pro les and applications to otation extraction and taxonomy Lynn

A technique is described that reŽ nes the standard sugar  otation procedure used to isolate nematodes from their surroundings. By centrifuging nematodes in a number of increasing speciŽ c gravity solutions and plotting the fraction  oating, the cumulative probability distribution of the population’s speciŽ c gravity is generated. By assuming normality, the population mean, m , and standard deviation,s, are found by a nonlinear least squares procedure. These density parameters along with their error covariance matrix may be used as a taxonomic physical character. A chi-squared test is derived for comparing populations. Mean and standard deviation pairs (m , s) were found for the speciŽ c gravities of the adult stage of the plant parasites Pratylenchus agilis (1.068, 0.017), P. scribneri (1.073, 0.028), P. penetrans (1.058, 0.008) and the bacterial-feederCaenorhabditis elegans (1.091, 0.016).