On The Influence Of The Environment Of The North And South Of China On The Reproductive Development Of Several Common Simocephalus Species

In this paper,703 samples were collected in 39 waters of 7 provinces in China,involving 6 species in the northern and southern common species.A preliminary study of their distribution range,distribution regular pattern,and growth in natural waters,and having a detailed study about 4 kinds of common simocephalus(simocephalus vetulus,Simocephalus serrulatus,Simocephalus sibiricus and Simocephalus himalayensis)of asexual reproduction,growth,development,population change and sexual reproductive.This paper cultured in the laboratory for 4 kinds of simocephalus collected in different seasons,and the results are summarized,the results showed that:in the different water environments of our country north and south,individual development and sexual reproduction of simocephalus has certain differences.The average number of fecundity of parthenogenetic individuals is more in the north at the same age,the highest fecundity is 27.3±2.4,the body length is larger than southern,and the largest body length is 2.474±0.172 mm.Living in high altitude(4500m-5000m)body length and fecundity of Simocephalus himalayensis in each age were higher than three simocephalus in other areas,the maximum body length 3.314±0.124 mm,the highest fecundity 33.2±1.7.Thus it can be seen,There's a certain impact about altitude differences and unique environmental characteristics of simocephalus growth and reproduction.In this paper,simocephalus vetulus as experimental samples,A observation of samples from two natural waters in Mudanjiang Heilongjiang and Hangzhou Zhejiang Province within two years.Two different kinds of water environment of low amount of Daphnia populations in whether the sexual reproduction of typical were observed.Two different kinds of water environments of simocephalus populations in whether the sexual reproduction of typical were observed,and a comparative study on the occurrence of sexual reproduction in the population was carried out.Samples of two waters in the north and south were compared with the method of artificial monoclonal and single population culture in natural waters.The annual autumn season simocephalus vetulus occurrence sexual reproduction with temperature decreased,Amphoteric reproduction(winter egg)individuals and sexual individuals(egg saddle)begin to appear in the population,The number of individuals in the population changes moreobviously in the stage of parthenogenesis.Results show,the typical sexual reproduction began to occur when the water temperature was 14.9 C in the end of September.Living in the southern water(Zhejiang,Jiangxi,Anhui)of simocephalus in autumn and winter sexual reproduction phenomenon without regularity,it is usually shown that there is no apparent sexual reproduction,or only signs of sexual reproduction according to water temperature change,and return to asexual reproduction as the water temperature rises.There is no significant sexual reproduction in the southern population under the same water temperature in the north,sexually reproductive individuals and male individuals rarely appear in the population,The number of parthenogenetic individuals accounts for the vast majority of the population.According to the observation statistics of the previous years,simocephalus in some waters in Hangzhou Zhejiang under the water temperature continues to a certain extent,the phenomenon of sexual reproduction occurs.Thus it can be seen,in the same species,they have adapted to the changes of their life cycle under the long-term water environment,for a long time it has become a phenomenon similar to geographical isolation,the difference of reproductive development between the same species is obvious.