Worm Breeder's Gazette 9(3): 13

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.

Was C. elegans Originally Associated with an Invertebrate?

G.O. Poinar, Jr.

It appears that a large proportion of rhabditoid nematodes found in 
the soil are associated with specific invertebrates, and of these 
nematodes, a large proportion are protandric hermaphrodites. 
There is a definite advantage in being associated with an 
invertebrate--it provides the nematode with a potential food source 
which becomes available when the invertebrate dies and is colonized by 
Since competition for this bacterial-rich source is great, an 
advantage is gained by nematodes which are 'on the spot.' The best way 
of achieving this is to be associated with the invertebrate before it 
dies. The hermaphrodite's advantage becomes apparent since time is 
valuable and a single amphimictic nematode has no opportunity of 
establishing itself. 
Most of the rhabditoid nematodes remain in the dauer stage while 
associated with the invertebrate (e.g. Rhabditis aspersa in snails, 
Rhabditis pellio in earthworms, Caenorhabditis dolichura in ants) and 
then initiate development as soon as the host dies. Recently Rhabditis 
myriophila, another hermaphrodite, was recovered from the gut of a 
milliped, and basically follows a cycle similar to the above-mentioned 
Other advantages of being associated with invertebrates are 
protection during adverse environmental conditions and distribution. 
Although the easiest way to recover specific rhabditoid species is 
to search for their associated invertebrate, all stages of these 
nematodes can also be found in soil when they are labelled freeliving (
ecological term) or microbotrophic (nutritional term). 
By just being a hermaphroditic rhabditoid nematode, the chances that 
C. nvertebrate associate somewhere out there 
are good.