الفهرس 
Normal development of Helisoma duryi
Embryonic development and time course of the ramshorn snail Helisoma duryi, (Wetherby, 1879Only 14 pages are availabe for public view
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Abstract
Embryonic development of the freshwater planorbid snail, Helisoma duryi, reared under laboratory-controlled conditions was described in detail. The morphological characters and the time
course of embryonic stages are presented. H. duryi generally lay egg masses at night or in the early morning hours. The egg type of H. duryi is isolecithal, and the cleavage is spiral holoblastic. After early cleavages followed by the appearance of the blastula, gastrula, and larval(trochophore, veliger,veliconch)stages,the fully developed young snail start hatched on the eighth day. Many unique developmental features in studied snail were observed and discussed.The present study focuses on comparing and studying the effectiveness of bulk zinc oxide (ZnO-BPs) and its nanoparticles(ZnO-NPs)on the reproductive performance and development of H. duryi, aiming to understand unique biological effects and mechanisms of action of both BPs and NPs and following up the teratogenic potency of ZnO. Both BPs and NPs were examined using numerous techniques. ZnO-NPs were found to be 11–31 nm in size and BPs were found to be around 154 nm as revealed by transmission electron microscope (TEM).