Worm Breeder's Gazette 10(2): 38

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Failure to Find Circadian Rythms in C. elegans

Eric Weiss and Bob Edgar

Since July of 1987 we have been investigating the possibility that C.
elegans exhibits circadian rhythms.  We are abandoning these studies 
now, but they may be interesting to others considering such research.  
Mainly, we looked for temporal changes in activity, oxygen consumption,
and sensitivity to temperature gradients in worms raised in 
light/temperature cycles.  After initial failures with adult nematodes,
we decided to use dauers; the primary reason for this was the 
relative ease of culturing large populations.  Also, we reasoned, 
since the dauer is the energy limited form of the organism it might 
gain some advantage from being active at specific times in the day.  
If analogy can be drawn between the dauer and infectious forms of 
parasitic nematodes, it seems logical that the nematode would benefit 
from being active when prospective hosts are active.  Dauers were 
prepared at first by starving large populations of wild type animals.  
Later, we used temperature constitutive daf mutants to get large 
populations quickly.  Problems arose with keeping dauers in liquid; we 
discovered that cultures that are disturbed fairly often become 
inactive or die in about two weeks.  This was ameliorated by 
suspending the animals in soft agar, which can be easily sampled 
without agitating the population.
Good methods for measuring oxygen consumption were never found, and 
experiments with radial temperature gradients were inconclusive.  Our 
main focus was the activity assay, which consisted of placing a drop 
containing a population of nematodes at the center of a ring of 
bacteria printed on an agar plate.  The animals disperse from the 
center and crawl around until they encounter the ring, in which they 
stop.  The fraction that make it into the ring by a certain time can 
be interpreted as some function of how active the population is.  
Interpretation of the data proved difficult; while there were distinct 
and large fluctuations in the activity during the day, these 
measurements were only marginally repeatable.  It seems that if the C. 
elegans dauer larva has circadian rhythms, they are best studied some 
other way.