Hatching of Schistosoma mansoni eggs and observations on motility of miracidia.

Eggs of Schistosoma mansoni were obtained from livers of mice and hatching was observed under varying conditions of light and ionic composition of the medium. Hatching occurred equally well in light and in darkness. Eggs also hatched readily in 1- to 50-m OsM solutions of urea, sucrose, sodium chloride, and glycerol, but hatching was inhibited at higher concentrations unless the eggs were left in solutions for long periods of time. Hatching readily occurred in deionized water, but the emerged miracidia did not swim longer than 5 to 10 min unless Na+ was added. Histochemistry of the egg showed DNA-positive egg granules and a polysaccharide-positive vacuole matrix. Acid mucopolysaccharides were stained in the vacuolar matrix and in the anterior sac of the miracidium. Longitudinal alignment of constituents of the egg shell is suggested by the predominance of longitudinal rents in the shell at hatching. A mechanism of hatching involving an osmotic stimulus is proposed.