The Early Larval Stages of Schistosoma mansoni Sambon, 1907 in the Snail Host, Australorbis glabratus (Say, 1818)

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Abstract
The mother sporocyst is an elongate, thin-walled sac which lies, tightly convoluted, usually near the external surface, in the head-foot region of the snail. From 200 to 400 daughter sporocysts are produced within each mother sporocyst by multiplication of the cells of the germinal line carried by the miracidium, which carries 50 to 100 germinal cells. Each of these germinal cells then gives rise to a daughter sporocyst embryo. No germinal masses were found in mother sporocysts. The daughter sporocysts leave the mother sporocyst and migrate to the digestive gland or, occasionally, to other organs of the snail. At the time of migration the daughter sporocyst is a small, elongate sac containing 50 to 100 germinal cells in the lumen. After reaching the definitive location the daughter sporocysts elongate and enlarge and ultimately give rise to numerous cercarial embryos. Most of the cercarial embryos arise from separate germinal cells which result from division of the germinal cells carried by the migrating daughter sporocysts. However, some of the germinal cells give rise to germinal masses which in turn produce cercarial embryos by a form of polyembryony. The cercariae leave the daughter sporocysts through a terminal birth pore. The stages are similar to those previously descr. for Trichobilharzia stagnicolae and Schistosomatium douthitti.
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