剪形臂尾轮虫形态的时空变化及其与生态因子间的关系

对芜湖市镜湖和汀棠湖中剪形臂尾轮虫(Brachionus forficula)的发生及其形态特征进行了一年的观察,并分析了其与环境因子间的关系。结果表明,镜湖中,剪形臂尾轮虫出现于7月至10月,且仅存在短后棘刺型个体;2样点内,除了前外棘刺长以外,轮虫的其他各形态参数均随季节显著变化,形态参数的样点间差异也因季节的不同而异;轮虫的各形态参数均随pH的升高而延长,随过滤水体中叶绿素a含量和水体中总叶绿素a含量的升高而缩短;体长和体宽均随晶囊轮虫密度的升高而增大。汀棠湖中,短后棘刺型个体出现于6月至10月,而长后棘刺型个体仅出现于6月至8月;2种形态型个体同时存在时,长后棘刺型个体在种群中所占比例始终高于短后棘刺型个体,并与水温、水体中总叶绿素a含量以及枝角类、桡足类和晶囊轮虫的密度均呈显著的正相关;2样点轮虫短后棘刺型个体各形态参数均随季节显著变化;长后棘刺型个体在1号样点内仅前外棘刺和后棘刺长有显著变化,而2号样点内仅体长、体宽和后棘刺长有显著变化;2样点内长后棘刺型个体的体长、体宽以及前外棘刺和后棘刺均显著长于短后棘刺型个体;同一形态型个体形态参数的样点间差异因季节的不同而异;短后棘刺型个体的前外棘刺和后棘刺长均与水体中总叶绿素a含量呈显著的正相关,后者与过滤水体中叶绿素a含量和枝角类密度也呈显著的正相关;长后棘刺型个体的后棘刺长与桡足类密度呈显著正相关,前内棘刺长与水温、溶氧量和晶囊轮虫密度呈显著负相关。两湖泊内剪形臂尾轮虫的后棘刺长和体长之间均呈显著的正相关,提示其后棘刺的延长并不是对体长的异速增长。

Spatio-temporal variation of morphometric characteristics of Brachionus forficula in relation to ecological factors

Cyclomorphosis is a common phenomenon which helps rotifers adapt to aquatic environments.To examine the mechanism and the ecological significance of cyclomorphosis of rotifers,the occurrence and the morphometric characteristics(body length,body width,and lengths of antero-median spine,left and right antero-lateral spines,and left and right posterior spines) of Brachionus forficula in Lake Jinghu and Lake Tingtang were investigated for one year,and the relationships between morphometric parameters and ecological factors(water temperature,pH,total Chl-a concentration,Chl-a concentration in water filtered through 25 μm net,SD readings,DO,N-NH-4 concentration,and densities of Asplanchna,all rotifers except Asplanchna,cladocera and copepod) were regressively analyzed.The results showed that in Lake Jinghu,B.forficula occurred from July to October,and all the individuals belonged to short posterior-spined morphotype.Except for the antero-lateral spine length,all the other morphometric parameters of the rotifers at the two sampling stations varied markedly with season.The differences in morphometric parameters of the rotifers between the two sampling stations also differed with season.All the morphometric parameters of the rotifers increased with increasing pH,but decreased with increasing total Chl-a concentration and Chl-a concentration in water filtered through 25 μm net.Body length and width of the rotifers both increased with increasing Asplanchna density.In Lake Tingtang,B.forficula individuals with short posterior spines occurred from June to October,but those with long posterior spines occurred only from June to August.When the two morphotypes occurred simultaneously,the proportion of the individuals with long posterior spines in the population was always higher than that of the individuals with short posterior spines,and correlated positively with water temperature,total Chl-a concentration in water and densities of cladocera,copepod and Asplanchna.All the morphometric parameters of the individuals with short posterior spines at the two sampling stations varied markedly with season.Only the lengths of the antero-lateral spine and the posterior spine at Station Ⅰ,and the body length and width,and the posterior spine length of the individuals with long posterior spines at Station Ⅱ varied remarkably with season.At the two stations,the body length and width,and the antero-lateral and posterior spine lengths of the individuals with long posterior spines were all significantly longer than those of the individuals with short posterior spines.The differences in morphometric parameters of the individuals with an identical morphotype between the two sampling stations differed with the season.The lengths of the antero-lateral spine and the posterior spine of individuals with short posterior spines were both positively correlated with total Chl-a concentration,and the latter was also positively correlated with Chl-a concentration in water filtered through 25 μm net and the density of cladocera.The posterior spine length of the individuals with long posterior spines was positively correlated with copepod density,and the antero-median spine length was negatively correlated with water temperature,DO and Asplanchna density.The posterior spine length of B.forficula in both the two lakes was positively correlated with the body length,indicating an absence of allometric growth of the posterior spine.