The Sexual Reproduction Biology Of Aurelia Sp.

In recent years, jellyfish have been blooming in the sea worldwide. In order to uncover the mechanism of outbreak of jellyfish, protect ocean ecology environment and fisheries resources, the researchers all round the world have been carrying out experiment to study them in some extent. The moon jellyfish Aurelia sp. is one species of the blooming jellyfish, which was caused great attention. It has been a hot point to study the life cycle of Aurelia sp.In this paper, the testis of male Aurelia sp. was studied. we observed the morphology changes of the male gonad under the condition of laboratory. meanwhile, the structure of different development stages of testis were studied by paraffin slice and histological staining techniques. The rules of the testis development of Aurelia sp. were grasped through the above research. The factors, such as photoperiod, food, damaged. that could induce the spermition of Aurelia sp. were studied according to experimental ecology. we also observed the process of spermition and fertilization, measured the activities of sperm of this species. In addition, the ultrastructure of sperm was studied by scanning and transmission electron microscopes. The detail result follows as:1. under the condition of 20’Cto 22℃, it needed about 40 days from ephyrae to medusae, which bell diameter and weight of medusae reached 7.50±0.71 cm and 28.70±6.60 g respectively. Meanwhile, the testis began to appear and develop. The testis became mature after 60 days’rearing, and its bell diameter and weight was 11.77±0.51 cm and 83.54±10.36 g, respectively. Moreover, the width of testis was about 1.05±0.08 mm at that time. The testis began to degenerate after 90 days since the ephyra stage, and almost disappeared at 110 days. The width and length both grew as the bell diameter being larger in the process of testis development. The process of testis maturation of Aurelia sp. was shown in figure 2. which showed the different growth stages of sperm follicles. The testis development can be divided into five stages that consist of phage Ⅰ (Early active stage),phage Ⅱ(Developing stage), phage Ⅲ(Ripe stage), phageⅣ (Spawning stage)and phage V (Spent stage)according to the tissue changes. Different portions of the testis were in different development phages. Different germ cells always in the same follicle but the same germ cells only in the same small follicle. This type of testis development of Aurelia sp. guarantee the persistence of the spermition, which is benefit for the long live for this species.2. The long photoperiod(14L:10D), starve and damage could affectively induced the sexual matured Aurelia sp. spermition. the vitality of sperm was also tested and relationship between Aurelia sp. percentage of active sperm and time was shown which indicated that the highest moving time and life span was 4 h 30 min and 10 h respectively (temperature,22℃; salinity,30 and pH,8.0).3. The maturated male gonads would release sperms once the environment was suitable. The maturated testis released sperm filament containing large amounts of sperms, then the sperm filament went through gastric circulation groove and gastric-oral arm groove successively, and left the body through oral arm groove finally. Female Aurelia sp. medusae captured sperm filament that the male released into food bag of somatic edge in which the sperm filament became sperm gobbet by tentacle, the sperm gobbets were transported into oral arm groove by oral arm, then they went through gastric-oral arm groove and gastric reproduction groove successively, and arrived at female gonad to fertilize finally.4. The fertilized eggs of Aurelia sp. were round and the diameter was about 150 u m. According to the appearance and characteristics of the embryo, embryonic development was divided into 6 consecutive periods:cleavage stage, blastulation stage,blastula stage, gastrulation stage, gastrula stage, planula stage and four tentacles scyphistoma. In 22±1℃ sea water, the embryo developed into planula at about 29 h 20 min and grown into four tentacles scyphistoma at about 73 h 20 min.5. The total length of spermatozoa of Aurelia sp. is about 33.62 μm, which is made of head, middle piece and tail. The head, likes a sharp chili in shape, is composed of acrosome and nucleus. There is a relative large gap between Plasma Membrane and Nucleolus Membrane, which is full of cytoplasm. The middle piece includes centriolar complex and mitochondrias, as well as sleeve structure. The proximal centriole and the basal body were arranged at an orthogonal, while the basal body was parallelled to the spermatozoon long axis. There has 4 mitochondrias, which were arranged like a cycle. The endomembrane of sleeve is fused with plasma memebrane of flagellum. The main structure of tail is a flagellum, consists of axoneme that is a typical "9+2" microtubular structure and wrapped by an wavy plasma membrane. In conclusion, The results indicate that the spermatozoa of Aurelia sp. were primitive type.The results above is a better supplement content of the life cycle of Aurelia sp. as well as fertilized biology, developmental biology and reproduction biology, which offers the vital information to uncover the mechanism of blooming of Aurelia sp. and has a positive reference value.