Studies On The Biology And Behavior Characteristics Of Sphaeroma In Mangroves In China

In recent years,substantial Sphaeroma outbreaks have seriously affected mangroves in China,especially in Dongzhai harbor National Mangroves Nature Reserve of Hainan province and Beihai National Mangroves Nature Reserve of Guangxi Zhuang Autonomous Region.However,the research on Sphaeroma is few.In this study,the species composition and population structure of Sphareoma were studied via molecular and morphological methods.The biology and burrow behavior characters of S.terebrans were also studied.The aims were to provide strategies for prevention and control of S.terebrans,and restoration of eroded mangrove ecosystems in China.1.The species composition of SphaeromaThe specimens of Sphaeroma were collected from Dongzhai harbor and Qinglan harbor of Hainan,Beihai of Guangxi,Zhanjiang and Shenzhen of Guangdong,Taipa island of Macau,respectively.A total of two species of genus Sphaeroma were found,including S.terebrans and S.retrolaeve.S.terebrans was the dominant species which eroded mangroves.The mitochondrial COI gene of S.terebrans which had morphological difference was analysed.Following that,the genetic distances,haplotypes diversity(h),nucleotide diversity(?)of S.terebrans populations were calculated to assess the level of genetic differentiation.The results revealed that the level of genetic differentiation was low among individuals with different phenotypes,and there was no cryptic species in the population of S.terebrans,indicating that the number of teeth on the uropodal exopod and the length of the propodus of the seventh pereopod could not serve as valid taxonomic characteristics.2.The growth and reproduction of S.terebransThe S.terebrans specimens were collected seasonally,the growth and reproduction of S.terebrans were analysed.The ranges of body length and weight of S.terebrans which had the ability to burrow were 3.50~10.00 mm and 0.0027~0.0690 g,respectively.The females of S.terebrans were 468,and the males were 332.The weight-length relationships of S.terebrans were: ? : W= 0.0001L2.7434(n=332,R2=0.6707),?: W= 6E-05L3.1005(n=468,R2=0.8271).The female was in positive allometric growth,the male was in negative allometric growth.The length-fecundity equations revealed that the body length had no significant correlation with absolute fecundity.The fecundity was different among different months.In March 2016,the fecundity was the strongest,the weakest was in June 2016.3.The experimental study on behavior of S.terebransS.terebrans not only burrowed mangroves,but also non-mangroves.S.terebrans had a different preference for substrates: Cystosepiment > Bruguiera gymnorrhiza >Aricennia marina > Heritiera littoralis > Brugu-iera sexangula.The hardness of different substrates was different: Bruguiera sexsngila > Aricennia marina > Heritiera littoralis > Bruguiera gymnorrhiza > Cystosepiment.The preference of S.terebrans for substrates was negatively correlated with the hardness of substrates.S.terebrans mainly distributed in the height of 0~50 cm under the water.The results demonstrated that S.terebrans prefered to live in 0~50 cm zone under the water.