NEMATODE (CAENORHABDITIS-ELEGANS) MOVEMENT IN SAND AS AFFECTED BY PARTICLE-SIZE, MOISTURE AND THE PRESENCE OF BACTERIA (ESCHERICHIA-COLI)

The movement of bacterial-feeding nematodes (Caenorhabditis elegans) t hrough sand was investigated using a range of sand sizes, equilibrated at a range of matric potentials, in the presence or absence of an att ractant source (Escherichia coli) at the distal end of a column. In th e presence of E. coli there was significantly greater movement of the nematode population towards the E. coli population, and the extent of the movement depended on the matric potential of the sand. Over time, an increasing proportion of the C. elegans population responded to the presence of the E. coli. The processes controlling these effects are discussed with respect to taxis and kinesis mechanisms of the nematode population, and with regard to the diffusive characteristics of the p hysical structure of the sand.