Reproductive characteristics and embryonic development of Bullacta exarata
Bullacta exarata is a unique gastropod in the coastal areas of the west coast of the Pacific Ocean.It is widely distributed in the northeast of China and the western coast of the Korean Peninsula,inhabiting the sandy or muddy beaches in the middle and lower intertidal zone.Due to its tender meat,delicious taste,and it is rich in protein,calcium,phosphorus,iron and a variety of vitamins,B.exarata has high edible and medicinal value,and its market value continues to rise.In addition,B.exarata has strong adaptability to temperature and salinity changes,and its growth speed is fast,so the artificial breeding market has broad prospects.At the beginning of this century,a large area of artificially cultivated B.exarata began to appear in the coastal areas of China.At present,B.exarata cultured on mudflat mainly comes from wild populations.However,the hatching rate of B.exarata eggs in natural sea areas is extremely low,and the hatching is not synchronized,resulting in a shortage of fry.Therefore,a deep understanding of the reproductive behavior and embryonic development patterns of B.exarata is of great significance for the development of artificial breeding techniques for B.exarata and for the promotion of industrial breeding of B.exarata.To study reproductive characteristics and embryonic development process of B.exarata,a batch of B.exarata and their egg masses were collected from the wild in June 2021,the size and quality of the egg masses and the number of eggs they carried were measured.The embryonic development of B.exarata under temperature(20±1)℃ was observed using microscopy and imaging system.The morphological characteristics of B.exarata at different development stages were recorded.The results showed that there was power function relation between egg mass size and egg number:the larger the egg mass was,the greater the number of eggs it contained.But there was no regular relation between egg mass quality and egg number.The average egg diameter of B.exarata embryos was 210 μm.The embryonic development of B.exarata could be divided into 6 stages and 16 periods according to the characteristics of B.exarata at different embryonic development periods.The fertilized egg began to crack at 50 min after fertilization,and after 23 h,the embryonic development of B.exarata entered the blastocyst stage.It took 31 h for B.exarata to enter the primary intestinal stage.After that organ formation began at 38 h 25 min.Experiencing 115 h 30 min after eggs laying,it eventually metamorphosed into juvenile shellfish.It was also found that it was crucial for embryo to get rid of the glial membrane as well as the temperature setting in the incubation process to improve the success rate and speed of incubation.This study aims to provide a theoretical reference and technical guidance for the artificial breeding and aquaculture of B.exarata at large scale.
万方数据
维普
