Worm Breeder's Gazette 8(1): 25

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.

Laser Microbeam Studies of Chemoreception

B.O. Davis Jr., M. Goode, D.B. Dusenbery

We have been using a laser microbeam to study the location of the 
sense organs used in C.  elegans chemotaxis to various chemicals.  
Electron microscopy has demonstrated that there are two types of 
likely chemoreceptors.  These are the two amphids, one of which is 
found on each of the lateral lips, and the inner labial sensilla, one 
of which is located on each of the 6 lips.  We do not attempt to 
selectively destroy the two sensilla located on a lateral lip, but 
rather damage both lateral lips with the objective of eliminating both 
amphids but only one-third of the inner labial sensilla.  When this is 
done and the nematodes are tested for response to various chemical 
stimuli, no change in response to Na+, D-tryptophan, C02 (pH6, 
phosphate buffer) or high (osmotic) NaCl is found.  The only exception 
to this pattern is that the response to cAMP was weakened or 
eliminated.  When all six lips were targeted, the response to Na+ 
weakened and even reversed in sign.  We conclude that the amphids are 
not the only chemoreceptor mediating responses to these chemicals, 
with the exception of cAMP.  It is suspected that the amphids detect 
stimuli that have not yet been tested.  The reversed response after 
all lips have been targeted is not understood and most of the rest 
lack one.  As expected, the HSNs are restored and the egg-laying 
defect of tra-2(n1106) is largely suppressed by ced-3, whereas other 
phenotypic indications of maleness are not.