Carbon Dioxide and Temperature Gradielits in Baermann Funnel Extraction of Rotylenchulus reniformis

Vermiform Rotylenchulus reniformis were anesthetized in water by 10-40% CO but were fully motile for 24 hours in water below 5% CO. When air containing 2.5% CO was blown onto agar, nematodes accumulated at the point of highest CO concentration. Nematodes also accumulated when chilling (0.2-1 C) of agar by the gas flow at the accumulation point was offset with heat from a fiber optic. In Baermann funnels containing R. reniformis in silt loam and sandy clay loam soils, CO in funnel water increased during 24 hours from 0 to ca. 1%; more CO accumulated below the soil layer than above. Bubbling air with 2.5% CO into water below soil in covered funnels increased the CO gradient and increased nematode extraction, whereas bubbling air without CO below soil purged CO from the water and decreased nematode extraction. Manipulation of CO within funnels usually increased extraction by only 30% and never by more than 3-fold. Controlling temperature gradients consistently increased extraction by 2-30-fold.