饵料种类及密度对透明溞繁殖和种群动态的影响

Effects of microalgal species and density on reproduction and population dynamics of water fleas Daphnia hyaline

为了研究饵料种类及密度对透明溞Daphnia hyaline繁殖和种群动态的影响,以蛋白核小球藻Chlorella pyrenoidosa、双对栅藻Scenedesmus bijugatus、四尾栅藻Scenedesmus quadricauda和沙角衣藻Chlamydomonas sajao 4种不同饵料(生物量均为7.5 mg/L),以及1.0×10^4、5.0×10^4、10.0×10^4、50.0×10^4、100.0×10^4 cells/mL 5种不同密度的蛋白核小球藻,分别培养北京密云水库透明溞,研究透明溞的寿命、生长、繁殖和种群动态变化情况。结果表明:用蛋白核小球藻、双对栅藻、四尾栅藻和沙角衣藻培养的透明溞内禀增长率rm分别为(0.310 2±0.025 0)、(0.292 3±0.030 6)、(0.292 9±0.031 7)、(0.252 1±0.018 9)ind./d,前3者之间无显著性差异(P>0.05),但均与后者有显著性差异(P<0.05);透明溞的寿命以双对栅藻最长,为(38.48±1.88)d,且与其他组有显著性差异(P<0.05);产前发育期以小球藻最短,为(6.80±0.74)d,各试验组间均有显著性差异(P<0.05);生殖总量以四尾栅藻最高,为(70.27±5.34)ind.,与其他组有显著性差异(P<0.05);饵料密度试验中,透明溞内禀增长率和净生殖率均随蛋白核小球藻饵料密度的升高而增大,内禀增长率最大为(0.357 6±0.015 6)ind./d,净生殖率最大为(83.54±8.80) ind.;而寿命随饵料密度升高先略有增加,之后快速减少;产前发育期随饵料密度的升高而降低。本试验结果可为透明溞规模化培养利用中,饵料藻类的选取和藻类密度的确定提供理论参考依据。

Lifespan, growth, reproduction and population dynamics were investigated in water fleas Daphnia hyaline collected from Miyun Reservoir in Beijing cultured in a SE medium incubator and fed four species of microalgae Chlorella pyrenoidosa, Scenedesmus bijugatus, Scenedesmus quadricauda and Chlamydomonas sajao and single C.pyrenoidosa at five cell densities of 1.0×10^4, 5.0×10^4, 10.0×10^4, 50.0×10^4 and 100.0×10^4 cells/mL at water temperature of 25 ℃ and photoperid of light∶dark=12 h∶12 h to explore for effects of microalgal species and density on reproduction and population dynamics of water fleas. It was found that the water fleas had intrinsic rates of increase(rm) of(0.310 2±0.025 0)ind./d in the medium of C.pyrenoidosa,(0.292 3±0.030 6) ind./d in the medium of S.bijugatus,(0.292 9±0.031 7)ind./d in the medium of S.quadricauda and(0.252 1±0.018 9)ind./d in the medium of C.sajao, without significant differences in r_m between the first three diets(P>0.05), and with significant different from that in the fourth diet(P<0.05). The maximal lifespan(38.48±1.88)days was observed in the water fleas fed S.bijugatus, significantly different from those in the water fleas fed the other three diets(P<0.05). The shortest period of prenatal development(6.80±0.74 days), was found in the water fleas fed C.pyrenoidosa, significant differences among the four diets(P<0.05). The water fleas fed S.quadricauda had the maximal reproductive capacity of(70.27±5.34)ind., significantly different from those in the water fleas fed the other three diets(P<0.05). The r_m and net production rate were shown to be increased with the increase in the algal food density within the five densities of C.pyrenoidosa, with the maximal r_m of(0.357 6±0.015 6)ind./d and net reproductive rate of(83.54±0.80)individuals. The life span, however, was increased slightly at first and then decreased rapidly with the increase in the diet density;the period of prenatal development was decreased with the increase in the diet density. The findings provide basis for the choice of microalgae as food and the optimal microalgal density in the large-scale culture and utilization of D.hyaline.