Aggregation and repulsion of nematodes at pH gradients

Abstract

Nematodes show a tendency to aggregate. This may be a result of their migration in response to a source of stimulation or it may occur purely as a chance phenomenon, i.e., the nematodes may get trapped at a particular spot. Wallace (1963) regarded this phenomenon to be of fundamental importance in the survival of nematodes. Bergman and Van Duuren (1959) working with Heterodera schachtii, Bird (1959) with Meloidogyne javanica, M. hapla, H. schachtii and Ditylenchus dipsaci, and Klingler (1961) with D. dipsaci, concluded that these nematodes do not aggregate at any particular pH. However, Bird (1959) showed that M. javanica and M. hapla were repelled at extreme levels of pH 3 and 10.6. Townshend (1964) reported that Aphelenchus avenae was repelled by Sclerotium rolfsii and attributed this repulsion to low pH conditions brought about by the fungus. Edmunds (1967) working with A. avenae concluded that aggregation was more evident at higher pH gradients.