Nematode specific gravity profiles and applications to flotation extraction and taxonomy

A technique is described that refines the standard sugar flotation procedur e used to isolate nematodes from their surroundings. By centrifuging nemato des in a number of increasing specific gravity solutions and plotting the f raction floating, the cumulative probability distribution of the population 's specific gravity is generated. By assuming normality, the population mea n, mu, and standard deviation, sigma, are found by a nonlinear least square s procedure. These density parameters along with their error covariance mat rix may be used as a taxonomic physical character. A chi-squared test is de rived for comparing populations. Mean and standard deviation pairs (mu, sig ma) were found for the specific gravities of the adult stage of the plant p arasites Pratylenchus agilis (1.068, 0.017), P. scribneri (1.073, 0.028), P . penetrans (1.058, 0.008) and the bacterial-feeder Caenorhabditis elegans (1.091, 0.016).