A primary study on the morphological changes of embryo of Hyriopsis cumingii in nurturing pouch of outer gill

The morphological changes of embryo of Hyriopsis cumingii in its nurturing pouch of outer gill were examined.It was found that,when the water temperature ranged from 20 ℃ to 23 ℃,the embryonic development from oosperm to mature glochidia took 11 days.After the oosperm sucked the water,the membrance swelt up and its size varied little,while the embryo bulged distinctly.The embryonic development of Hyriopsis cumingii might be divided into four stages: oosperm,cleavage,gastrulae and glochidia.The length of embryo increased 82.8% during the whole embryonic development.The growth rate of late embryo was higher than that of early embryo.The highest growth rate was observed in gastrulae stage and glochidia stage.There were relations between different stages of the embryonic development and the character of the outer gill of the female.