The feeding biology of two bacterivorous nematodes found in percolating filter-bed sewage treatment plants were investigated in relation to food supply and temperature at all developmental stages. Temperature profoundly affected feeding activity and ingestion rates. As temperature increased ingestion rates increased. The larger species, Rhabditis curvicaudata possessed lower rates of pharyngeal pulsation than the small species Diplogasteritus nudicapitatus. R. curvicaudata reduced feeding activity as bacterial density fell from 8x10 cells ml to 5x10 cells ml, below which it ceased feeding. D. nudicapitatus pumped continuously at a more or less constant rate irrespective of food density. The evolutionary and ecological aspects of these two patterns of feeding behaviour are discussed.
The growth, reproduction and longevity of Diplogasteritus nudicapitatus, Paroigolaimella bernensis and Rhabditis curvicaudata were investigated under conditions of excess food within the temperature range 5°C-20°C. In all three species growth rate increased with temperature, and in D. nudicapitatus and R. curvicaudata the adult size attained varied significantly with temperature. P. bernensis did not reproduce at 5°C, but showed a progressive increase in reproductive output at higher temperatures. D. nudicaitatus showed increased egg production as temperature increased while R. curvicaudata had maximum egg output at 10°C. Longevity is temperature dependent, decreasing with higher temperatures. Virgin females survived for longer than reproducing females. The data indicate that while D. nudicapitatus and P. bernensis are thermophilic species, R. curvicaudata is adapted to lower temperatures.
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