While much is known of the morphological and some physiological changes which occur during the aging of Caenorhabditis elegans, little attempt has been made to measure the changes in behaviour. Wild type C. elegans (var. Bristol) were cultured axenically, individually observed each day for 15 minutes and their behavioural actions recorded on a multi-channel event recorder or on a video tape recorder of a closed circuit TV_- Particular attention was paid to the rate of backwardly directed somatic waves, pharyngeal bulb pulsations, the interval between defecations and oviposition.

C. elegans lived significantly longer in axenic culture than in bacteria. A gradual linear decline occurred in the rate of backward waves between maturation (day 4) and death (day 20) for those worms in axenic culture. In striking contrast, the mean maximum rate of pharyngeal bulb pulsations maintained a plateau from day 4 to 18, while the mean interval between defecations doubled from 60 sec (days 4 to 8) to 120 sec (days 10–20). These results are discussed in the context of nematode coordination and the mechanisms of aging.