| Abstract: | Weekly core samples of sewage sludge were taken in an effort to correlate independent variables such as depth, biological oxygen demand, moisture, and temperature with a dependent variable (nematode abundance). A multiple regression analysis indicated that the independent factors produced a significant effect on nematode numbers, but the correlation was neither consistent nor predictable from one sampling period to another. There were instances where the observed independent variables showed no statistical evidence of producing an effect on the dependent variable. Fluctuations in nematode quantities were possibly influenced by other factors which were not considered: predation, disease, and natural enemies of nematode populations has not been critically evaluated. The genera of nematodes inhabiting sludge were found to be similar to those reported by previous workers. The nematode species and the predominant population were considerably different from those reported in sewage elsewhere. Rhabditids appeared as the predominant population while diplogasterids showed only spasmodic population peaks, then they declined or disappeared over the summer months. The population of rhabditids peaked in May and then gradually declined, but never disappeared. At times the rhabditids made up 99% of the total population. A fungal contaminant, Aspergillus sp., was found to produce a toxic substance which killed all growth stages of Pelodera chitwoodi cultured in an artificial medium. It was shown that Aspergillus filtrate destroyed nematodes, but had no adverse effects on bacteria growing in the same culture dish. A method for mounting the entire rhabditid male for displaying the bursa in glycerin jelly was described. The process of intestinal elimination for the female P. chitwoodi was observed and described. The intestine was found to contain viable bacteria. |
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