The development of a standard method for rapid ecdysis of infective Haemonchus contortus cayugensis larvae

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Abstract
Infective Haemonchus contortus cayugensis larvae were rapidly exsheathed (20 min) using 0·02 m-Na2B4O7. 10H2O, a gas mixture of 40 % CO2–60 % N2, and subsequent aeration with compressed air as reported previously. Several variables in this system were examined. The optimum concentration of sodium tetraborate was found to be 0·02 m. The exsheathment rate decreased with increasing molarities of the salt over the range 0·02–0·08 m. Exsheathment rates were low when the larvae received the full stimulus to exsheath for only 5 and 10 min before aeration. The larvae required at least 15 min of the full stimulus before aeration to ensure high exsheathment rates. The rapid method of ecdysis caused no abnormalities in or death of larvae, and all the larvae at the end of the incubation period were very motile and appeared normal. The exsheathment rate was consistently high as the larval concentration was increased from 2 ×103 to 2×106/10 ml of 0·02 m-Na2B4O7. 10H2O.