THE IN VITRO HATCHING OF ASCARIS LUMBRICOIDES EGGS

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Abstract
The stimulus leading to in vitro hatching of Ascaris lumbricoides eggs consisted of four components as follows: (1) a temperature similar to that of homoiothermic animals, (2) pCO2 approximating 5 vol.%, (3) pH near 7.0, (4) non-specific reducing conditions such as are established by cysteine, glutathione, sodium hydrosulphite, sodium bisulphite, or sulphur dioxide. Application of this stimulus resulted in 80–95% hatching in 3 hours, the observed morphological changes corresponding to those occurring during intestinal hatching. The stimulus was not effective when applied to preinfective stages of embryonic development, or to infective eggs which were embryonated in 2% potassium dichromate solution. Maximal hatching was obtained when the stimulus was applied continuously. One of the first results of stimulation may be increased permeability of the vitelline membrane sufficient to permit the outward passage of enzymes such as chitinase which digest the chitinous shell. There is no reason to believe that the in vitro stimulus differs significantly from the natural stimulus, which is common to many homoiothermic animals and may account in part for the low degree of host-specificity in Ascaris infections.

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