Studies On The Biology And Ecology Of Sphaeroma In Guangxi Mangrove Region

In recent years,there has been an outbreak of Sphaeroma in a number of mangroves in China,where a countless number of Sphaeroma have been eroding mangrove plants,resulting in aggravating degradation of mangrove ecosystem.In particular,the mangrove forests in Guangxi are severely affected by Sphaeroma,but there are few reports on the investigation of Sphaeroma in this region.In this study,histological section technique was used to study the oogenesis of female Sphaeroma terebrans in Xiaoguansha mangrove of Beihai city in Guangxi province,and a field survey was conducted in accordance with the presence or absense of Sphaeroma terebrans ’s larvae in this area,in order to explore the breeding period of Sphaeroma terebrans;Then,we analyzed the species composition and distribution characteristics of Sphaeroma at the managrove forest in Guangxi,in order to discuss the relationship between mangrove degradation and Sphaeroma;In this paper,three seriously-jeopardized mangrove forests in Beihai city of Guangxi were investigated in terms of their degradation degree,to further explore the relationship aOC6ng mangrove degradation degree,Sphaeroma and environmental factors.The above study is purposed to provide theoretical reference for seeking OC6re effective countermeasures to prevent and control Sphaeroma,as well as recover the mangrove ecosystem.Here are the results of this study as follows:(1)Female Sphaeroma terebrans were collected from Xiaoguansha mangrove of Beihai city,Guangxi Province.Then,tissue section experiments were conducted on them to observe the oogenesis of them.Besides,at each sampling,it was necessary to observe and record whether there were larvae of Sphaeroma terebrans on the sampled ground.The results showed that the oogenesis of female Sphaeroma terebrans could be divided into three stages:oogonium,previtellogenic oocyte and vitellogenic oocyte.AOC6ng them,the previtellogenic oocyte could be divided into three sub-stages,including OC1 oocyte,OC2 oocyte and OC3 oocyte;The vitellogenic oocyte could be divided into three sub-stages,including OC4 oocyte,OC5 oocyte,and OC6 oocyte.During the period from the end of February to March of a year,no mature oocytes and embryos were found in females of Sphaeroma terebrans,but at other times,mature oocytes and embryos were found in them;During the period from the end of February to April of a year,no larve of Sphaeroma terebrans was found in the sampled ground,but their larves were found at other times.Therefore,we concluded that the breeding period of Sphaeroma terebrans was the full year with the exception of the period from the end of February to March.(2)By investigating 30 sections in Guangxi mangrove region on the spot,and collecting the local samples of Sphaeroma,we observed and recorded the distribution characteristics of Sphaeroma in each section in order to analyze the species composition and distribution characteristics of Sphaeroma in Guangxi mangrove region,and discussed the relationship between Sphaeroma and degradation of mangrove ecosystem.The results showed that the species composition of Sphaeroma includes three species:Sphaeroma terebrans Bate(1866),Sphaeroma retrolaeve Richardson(1904)and Sphaeroma fujianensis sp.nov.AOC6ng them,Sphaeroma terebrans was the main specie of Sphaeroma in this area,followed by Sphaeroma retrolaeve,while the Sphaeroma fujianensis appeared in three sections in Beihai city of Guangxi province.This was the first time that Sphaeroma fujianensis had appeared in the mangroves in Guangxi province.Sphaeroma mainly distributed in the tidal creek of the low-tide and high-tide areas and on both sides of it,as well as forest edge,and these areas were low-lying.A few Sphaeroma distributed in the high tide area,while others distributed in the forest.In this study,the substrates of Sphaeroma were varied,including mangrove plants,timber piles,Styrofoam and soft sedimentary rock.(3)By investigating these three areas of mangrove forests seriously affected by Sphaeroma including Baisha Herong,Dongwei and Xiaoguansha in Beihai city of Guangxi province,the relationship aOC6ng the degradation degree of mangrove forest,Sphaeroma and environmental factors was probed.As indicated in the results,the damaged degree(i.e.degree of degradation)of Baisha Herong mangrove forest was the largest,followed by that of Dongwei and Xiaoguansha mangrove forests,and which of the latter two were similar.All these three areas are attacked by Sphaeroma,and the Sphaeroma specie endangering the mangrove forest of Baisha Herong and Xiaoguansha was Sphaeroma terebrans,while the Sphaeroma species jeopardizing Dongwei mangrove forest included Sphaeroma terebrans,Sphaeroma retrolaeve and Sphaeroma fujianensis,which shows that the Sphaeroma terebrans distributed OC6re widely.Around the mangrove forests of Baisha Herong,Dongwei and Xiaoguansha,the coastal aquaculture was developed,and the waste water discharged from which is untreated.The eutrophication degree of water in the mangrove forest of Baisha Herong was the highest;In addition,the affected communities of Baisha Herong mangrove appeared in the center of patches,while those of Dongwei and Xiaoguansha mangrove forests appeared near tidal creek and forest edge;Apart from this,it was also found that there were habitat and nest of herons in these three areas.The above results indicated that the larger degree of environmental pollution around mangroves,the greater the damage of Sphaeroma to mangroves,and the OC6re serious the degradation of mangroves.