The action of insect juvenile hormone on the hatching of eggs of the nematode, Haemonchus contortus, and its role in the development of infective and non-infective stages

Abstract

1. 1. With a gas phase of CO 2-free air the inhibitory action of the analogues of juvenile hormone, “dichlorofarnesoate” and farnesol (JH) on the hatching of eggs of Haemonchus contortus was markedly affected by [H +]. The pK of the inhibitory effect was 6.8; above pH 7 inhibition was weak, below 6.5 it was strong. 2. 2. The inhibition of hatching of eggs in 0.1 M NaCl containing JH, 3 × 10 −4 M, and under a gas phase of air, increased as the temperature was raised from 20 to 37°C. 3. 3. In buffer at pH 6 and under air, increases in temperature to 37°C did not inhibit hatching in the absence of added JH. However, when CO 2 was removed from the gas phase hatching was inhibited at the higher temperatures. 4. 4. Acetazolamide, 10 −3M, and ethoxyzolamide, 2 × 10 −5 M, inhibited the exsheatment (ecdysis) of third stage juveniles of H. contortus. 5. 5. The significance of these results in providing a hypothesis for features in the life cycle of nematodes, and in providing a hypothesis describing the action of JH on the target cell, is discussed.