温度和培养体积对大型溞种群动态和两性生殖影响的研究

研究了5个培养体积(50、100、200、400、1000 mL)和2个温度(20℃、25℃)下大型溞(Daphnia magna Straus)种群动态和两性生殖的变化,结果表明:(1)在相同培养体积下,随温度升高,大型溞首次抱卵时间缩短、首次产幼涵时间提前.在相同温度下,大型涵首次抱卵体长随培养体积的增大而增大.20℃和25℃下,1000 mL组大型溞首次抱卵体长分别是(2.54±0.02)mm和(2.71±0.01)mm.(2)在一定时间内,大型溞种群数量快速增加.但在较小培养体积下大型溞种群增长明显受到抑制.20℃和25℃下1000 mL培养体积组最大种群数量是2152 ind./1000 mL和3085 ind./1000 mL,分别约为50 mL组的4倍和13倍.培养体积与大型溞最大种群数量间存在显著相关性(P<0.01,n=15).(3)所有种群实验组均产生雄体,且雄体数量随种群数量的增加而相应增加.20℃下1000 mL组产生的雄体数量明显高于其他培养体积组,最大比例可达36%,且第一次产幼溞即出现雄性.雄体数量与大型溞最大种群数量之间呈显著的相关性(20℃:P<0.01,n=15;25℃:P<0.05,n=15).(4)20℃和25℃下,1000 mL组大型涵累计产生卵鞍分别为814和359个,且均由母溞后代形成.而其他体积组仅产生少量卵鞍或不产卵鞍,且所产卵鞍均由培养时的母溞形成.20℃和25℃下1000 mL组所产卵鞍的空卵鞍率分别达61.18%和99.16%.实验期间,20℃、1000 mL组所产生的卵鞍中,含休眠卵的比例均在20%以上.

Effect of temperature and culture volume on population dynamic and sexual reproduction of Daphnia magna straus

Under two temperatures(20℃ and 25℃ )and five culture volumes(50, 100, 200, 400 and 1000 mL) , population dynamic and sexual reproduction of Daphnia magna which came from Huaihe river were studied in this paper. The results showed that: (1) At same culture volume, the mature time and the first brood time of D. magna shortened with the increase of temperature. The mature body length of D. magna increased with the increase of culture volume at same temperature. The mature body length of D. magna in the 1000 mL group was (2.54±0.02) mm at 20℃ and (2.71±0.01) mm at 25℃. (2) At the initial stage, the population size could increase rapidly through parthenogenesis. However, population growth of D. magna was evidently limited at lower culture volumes. The maximal population size of D. magna in the 1000 mL group were 4 times at 20℃ (2152 ind. /1000 mL) and 13 times at 25℃ (3085 ind. /1000 mL) higher than that in the 50 mL group. It had significant relationship between the maximal population sizes of D. magna and culture volumes (F<0.01, n = 15 ). The first brood size of D. magna were (96.0±36.4) ind. /50 mL, (82.3±25.1) ind. /100 mL, (328.0±28.8) ind. /200 mL, (296.7±36.7) ind. /400 mL and (290.3±27.0) ind. /1000 mL at 20℃: , and was (44.3±3.1) ind./50 mL,(64.0±11.4)ind./100mL,(283.7±5.5) ind./200mL, (524.3±18.7) ind./400 mL and (525.7±26.8) ind./1000 mL at 25℃, respectively. (3) During the experiment, the males occurred in all the groups. The number of male of D. magna increased with the increase of population size. The number of male of D. magna in the 1000 mL group was obviously higher than that in other culture volumes at 20℃, and the highest male percent reached 36%,and the males was induced in the first broods. The number of male was positively correlated with the maximal population size of D. magna (20℃: P<0.01, n=15;25℃: P<0.05 , n=15). (4) It was totally produced 814 ephippia at 20℃ and 359 ephippia at 25℃ in the 1000 mL group, which produced by the offspring of the mother, while a few ephippia were produced by the mother or no ephippia appeared in the other groups. The percent of empty ephippia among ephippia was 61.18% at 20℃ and 99.16% at 25℃ in the 1000 mL group. During the experiment, the percent of ephippia containing the resting eggs in the 1000 mL group was up to 20% at 20℃.It was likely that lower temperature and population size might be two important factors that caused sexual reproduction and produced the resting eggs in D. magna.