Studies On Reproduction And Development In Daphnia(Ctenodaphnia) Carinata

Cladocera, generally speaking named daphnia, was one kind of the zooplankton in fresh water and it subjected to Crustacea, Arthropoda. Ways of reproduction in Cladocera were quite interesting. There were two types of reproductive modes. When the environmental conditions were very suitable, parthenogenesis was the dominate reproductive mode. However, it would convert into sexual reproduction under environmental stressors, such as temperature changing, food lacking, community density excessing, and so on. Cladocera was also a kind of important economic aquatic animal. For one thing, it had a high protein contents(40%-60% of dry weight). For another thing, it was an ideal and important living diet in fishery farming because of its abundant amino acids, vitamins and calcic ingredients. All these elements were very important to the growth and development of many economic animals such as fish, shrimp and crab. Recently, with the development of the fishery farming and larva breeding, there was an increasing demand of Cladocera and the large-scale artificial culture in production of Cladocera was needed to meet the seasonal demanding. Therefore, it was promising to have further study in the developmental biology of Cladocera, ascertained the rules and mechanisms of reproduction and development in Cladocera, then actualized the artificial regulation of the growth and development in Cladocera.Research towards Cladocera could be dated back to the early period of 18th century. The early reports on Cladocera were limited in the description of the external morphology. It was not until the middle of 19th century, under the great progresses of the productive practices in fishery, that the investigation and research on Cladocera developed greatly. So far, many scholars all over the world had done quite a number of researches in Cladocera, on the field of the morphology, population ecology, idioplasm genetics, environmental evaluation and toxicology, ect. As we all knew, many researchers were very interested in studying the reproductive biology of Cladocera. The main researches were focused on Cladocera reproductive biology including description of the reproductive system, affects of environmental factors changes on the fecundity and reproductive amount, the microstructure and ultrastructure of the sexual eggs, and so on, but reports on the mechanism of thereproductive conversion in Cladocera were very little, and those were only concentrated on induction of some environmental factors in reproductive conversion. As to the germ cells genesis, the chromosome behavior, the changes of the isoenzyme activity and protein constitution as well as function during different reproductive states in Cladocera, few reports had been elucidated so far. These works were not only the bases of studies on the reproductive biology in Clacdocera, but also the precondition of further understanding the life essence in Cladocera from macroscopy, microscopy, to cell level and molecule level. So the research of this paper had both practical and theoretic values.This paper preferred the Daphnia(Ctenodaphnia) carinata, a common species in fresh water, as the experimental animal. Based on describing its external morphologies, our study intended to do some researches on germ cell genesis, chromosome behavior and isoenzyme activity during the different reproductive states, then explore the constitution and function of changing proteins from the parthenogenetic to sexual mode using the new technology of proteomics, and meanwhile analyze its embryo developmental and biochemical components. We tried to make a brief introduction about rules and mechanisms of reproduction and development which would make a good base to further study the actual mechanism of reproductive conversion in Cladocera. These researches would not only had practical significance in the artificial culture of Cladocera and the cultivation and breeding of large-scale aquatic products, but more importantly these could prolongate and enrich the theories of reproductive biology in Crustacea, and even...