| Hyriopsis schlegelii is developed as a high-quality freshwater pearl mussel in recent years in China. And it was also widely cultured to produce pearls in aquaculture. So far, there have been reports on genetic breeding of H. schlegelii, its disease-resistant genes, and so forth. But the studies on biology of reproduction for H. schlegelii remain rare. In this present works, we mainly focused on the researches of its reproductive biology including morphology, motility and survival time of sperm, as well as understanding whether the mussel could propagate in winter and exploring the possibility for self-fertilization, which would contribute to the sustainable use of this mussel resource. The results are shown below.1, The movement and survival time of the sperms from H. schlegelii when in three matrixes were observed by dyeing. The semen from gonad was drawn into saline solution, pond water and distilled water, respectively. Then, the results were examined by microscope and staining of sperm based on eosin Y (concentration of0.1%) every30minutes as only dead sperms can be dyed red while living sperms can not be stained. The results showed that the longest survival time of the sperms was in normal saline, and the shortest survival time was in pond water. The sperm was observed to possess a bullet-shaped head and a flagellum-like tail. The total length, head length and head width of the sperm was254.91±20.03μm,32.33±2.15μm, and16.60±3.29μm, respectively. And the length of sperm tail was about216.67±19.73μm. The motion mode of sperm contains three ways:fast linear motion, curved rotation and swaying movement.2, Male and female H. schlegeliis of reaching sexual maturity were polycultured and hung in the isolated pools where there were no other mussels. By means of frozen serial section examination of the morphological changes of embryo in its nurturing pouch of outer gill through HE staining when sampling termly, the nurturing pouch is not development from November to the next March, showing a small but circular shape. And the outer gill was wizened and darker in color. Up to April, its outer gill started to develop. And the nurturing pouch expanded an elongated and large cubage, unfolding gradually a plump shape, and usually with a fine gloss for it, and pale yellow color with hints of white block. Importantly, many embryos can be found in nurturing pouch in this time under microscope, which suggested that it did not reproduce in the course of November to the next March while stated to produce offspring from April for H. schlegelii.3, To investigate whether self-fertilization occur in H. schlegelii, male and female mature H. schlegeliis were isolated and raised in the separate pools where no other mussels existed, sampling at a month interval to detect the number of the embryo in its nurturing pouch of outer gill by using frozen continuous section were carried out. The results showed that no one embryo was found in nurturing pouch of H. schlegeliis sampled from November to the next March. And the similar result also occurred to H. schlegeliis sampled from April, although its nurturing pouches have already formed very well, implied that there is no self-fertilization phenomenon in H. schlegelii, and the development of its nurturing pouches did not need the stimulation of embryo. |
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