Undissociated bases as the stimulus for the development of early parasitic stages of nematodes

Petronijevic T. and Rogers W. P. 1987. Undissociated bases as the stimulus for the development of early parasitic stages of nematodes. International Journal for Parasitology 17 :911–915. The effects of NH₄Cl and NH₂CH₃ on infective stages of Haemonchus contortus, Nematospiroides dubius and Ascaris suum have been compared with the action of H₂CO₃. Detailed experiments were carried out with H. contortus. NH₄Cl at pH 8 under air was less toxic to infective stages than it was to free-living juveniles of Panagrellus redivivus. The induction of exsheathment or hatching by bases was slow (20–30 h) though the time of development of 4th stage H. contortus was not proportionally increased. Activity at pH 6 was less than that at pH 8. In contrast to the action of H₂CO₃ as the stimulus, NH₄Cl was not Ca²⁺-dependent. Prolonged exposure to anoxia at pH 8 was toxic, but in the presence of NH₄Cl or H₂CO₃ toxicity was decreased. The inhibition of exsheathment due to Dnp at pH 7 was greater when NH₄Cl was the stimulus.The process whereby host signals induce development of parasitic stages is discussed.