温度和食物密度对两种形态型裂足臂尾轮虫(Brachionus diversi-cornis)生活史特征和后代形态型的影响

Effects of temperature and algal density on life history characteristics and morphotype in offspring of two Brachionus diversicornis morphotypes

运用单个体培养方法研究了温度(15℃、20℃、25℃和30℃)和斜生栅藻(Scenedesmus obliquus)密度(0.75×106、1.5×106、3.0×106和6.0×106 cells/ml)对等棘刺型和不等棘刺型裂足臂尾轮虫(Brachionus diversicornis)的净生殖率、种群内禀增长率、世代时间、生命期望和后代混交率等生活史参数和后代形态型的影响.结果表明:各温度下,两种形态型轮虫的存活率无显著差异;除20℃外,其余三个温度下,等棘刺型轮虫的繁殖率显著高于不等棘刺型;除30℃下等棘刺型轮虫的世代时间长于不等棘刺型轮虫外,各温度下两种形态型轮虫的各生活史参数均无显著差异.各食物密度下,两种形态型轮虫的存活率、繁殖率、各生活史参数也均无显著差异.两种形态型轮虫的种群内禀增长率、世代时间和生命期望对升高的温度反应不同,但食物密度仅对等棘刺型轮虫的净生殖率和内禀增长率有显著影响.等棘刺型轮虫的净生殖率在6.0×106cells/ml食物密度下显著低于0.75×106和3.0×106cells/ml食物密度下,1.5×106cells/ml食物密度下与上述三食物密度间均无显著差异;内禀增长率在6.0×106cells/ml食物密度下显著低于3.0×106cells/ml食物密度下,但两者均与0.75×106和1.5×106 cells/ml食物密度下无显著差异.在各温度和食物密度下,两种形态型轮虫都能产生等棘刺型和不等棘刺型的后代.25℃下等棘刺型轮虫所产后代中等棘刺率明显高于不等棘刺型轮虫,但各食物密度下两种形态型轮虫所产后代中等棘刺率无显著的差异.温度对等棘刺型轮虫所产后代中等棘刺率有显著的影响,但食物密度对两种形态型轮虫所产后代中等棘刺率均无显著的影响.等棘刺型轮虫所产后代中等棘刺率在15℃和25℃、20℃和30℃间分别无显著差异,但前两者显著高于后两者.

Effects of temperature（15℃,20℃,25℃ and 30℃） and Scenedesmus obliquus density（0.75×106,1.5×106,3.0×106 and 6.0×106 cells/ml） on life history parameters including net reproductive rate,intrinsic rate of population increase,generation time,life expectancy at hatching and proportion of mictic offspring,and morphotype in offspring of two Brachionus diversicornis morphotypes were studied by means of individual culture.The results showed that at the four temperatures,the survivorship between the two B.diversicornis morphotypes was similar.The fecundities of the equal-spined rotifers at 15℃,25℃ and 30℃ were significantly higher than those of the unequal-spined rotifer.Each of the life history parameters between the two B.diversicornis morphotypes was similar,except that the generation time of the equal-spined rotifers was longer than that of the unequal-spined rotifers at 30℃.The survivorship,the fecundity and each of all the life history parameters between the two B.diversicornis morphotypes were also similar at the four food densities.All the intrinsic rate of population increased,the generation time and the life expectancy at hatching of the two B.diversicornis morphotypes responded differently to increasing temperature,but food density only affected the net reproductive rate and the intrinsic rate of population increase of the equal-spined rotifers significantly.The net reproductive rate of the equal-spined rotifers at algal density of 6.0×106 cells/ml was lower than that at both 0.75×106 and 3.0×106 cells/ml,and the net reproductive rate at 1.5×106 cells/ml was similar with that at each of all the above-stated three food densities.The intrinsic rate of population increase of the equal-spined rotifers at 6.0×106 cells/ml was lower than that at 3.0 ×106 cells/ml,but both of them were similar with those at 0.75×106 and 1.5×106 cells/ml.At each of the four temperatures and food densities,the two B.diversicornis morphotypes produced both equal-and unequal-spined offspring.Only at 25℃,the proportion of equal-spined offspring produced by the equal-spined mothers was higher than that produced by the unequal-spined mothers.However,at each of all the four food densities,the proportion of equal-spined offspring produced by the two B.diversicornis morphotypes was similar.Temperature affected the proportion of equal-spined offspring produced by the equal-spined mothers significantly,but food density did not affect the proportion of equal-spined offspring produced by both the equal-and unequal-spined mothers.The proportions of equal-spined offspring produced by the equal-spined mothers at 15℃ and 25℃,and 20℃ and 30℃ were similar,respectively,but the former two were higher than the latter two.