Worm Breeder's Gazette 5(2): 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.
Analysis of serial sections through the head of CB1377 (daf-6,X), a nonchemotactic dauer-defective mutant, indicates that the primary defect may be in the amphidial sheath cells. In L2 larvae, the amphid channels are open at the tip of the nose but are closed off posteriorly, apparently by 'overgrowth' of the sheath cells. In wild- type L2's amphidial neurons e-1 extend to within 1 m of the tip of the nose, but in the mutant only two ciliated processes are observed 2 m from the tip. These neurons project into the channel block. Farther back, bent cilia project laterally into the sheath cell. Approximately 6 m from the tip of the nose, the cilia are nearly wild- type in structure and organization. The CB1377 phenotype is much more severe in the adult, Numerous large, membrane-bound vesicles are located throughout the lateral and ventral regions of the head, whereas these vesicles are confined to the lateral (amphid) regions of the L2. The amphid channels are not observed in transverse serials through the first 8 of the head although they are present farther back. As in the L2, the tips of the amphid neurons are distorted and of different lengths. Scanning electron micrographs of the mutant adult provide no external evidence for the existence of amphids. The lateral outer labial neurons are also affected, perhaps indirectly. One lateral outer labial in the L2 appeared to be missing. The area in which this neuron is normally located is occupied by enlarged sheath cell. Neither lateral outer labial neurons could be located in the adult. Subdorsal and subventral outer labials are normal in individuals of both developmental stages.