温度对发头裸腹溞(Moina irrasa)种群动态和两性生殖的影响

Effect of temperature on population dynamic and sexual reproduction of Moina irrasa

在食物浓度为4×105cells/ml栅藻的条件下,研究了4种温度(15、20、25、30℃)对发头裸腹溞种群动态及两性生殖的影响.结果表明,在4种温度下,发头裸腹溞种群密度在实验初期逐渐增大,达到密度最大值后呈现下降的趋势.随着温度的升高,发头裸腹溞成熟时间、首次产幼溞时间以及达到最大种群密度所需时间均缩短,但母溞成熟时的体长及首次所产幼溞体长则呈缩短的趋势.除30℃外,随着温度的升高,发头裸腹溞最大种群密度依次增大.4种温度下,发头裸腹溞的平均最大种群密度分别是882±136ind./(200ml)、1351±141ind./(200ml)、1643±105ind./(200ml)和1226±82ind./(200ml).发头裸腹溞在所有实验组均产生雄体及卵鞍,且雄体密度随种群密度的增加而增大.发头裸腹溞平均最大雄体密度和最大累积卵鞍数均出现在25℃,分别为169ind./(200ml)和1444ind./(200ml).研究表明温度过高或过低都不利于发头裸腹溞的种群增长,且发头裸腹溞的卵鞍形成倾向于受温度、食物和种群密度的共同影响.

Population dynamics and sexual reproduction of Moina irrasa were studied under four temperatures（15,20,25,30℃） and food concentrations of 4×105cells/ml.The results showed that population density of M.irrasa presented a trend of gradual increase at first stage and decreased after it reached the density peak under four temperatures.With the increase of temperature,mature time,first reproduction time and the time reaching maximal population density declined,while body length of mother at mature and first offspring-produced decreased.In addition,the maximal population density of M.irrasa increased with increasing temperatures except 30℃.Mean maximal population densities of M.irrasa were 882±136ind./（200ml）,1351±141ind./（200ml）,1643±105ind./（200ml）,1226±82ind./（200ml） under four temperatures,respectively.The males and ephippia of M.irrasa were observed in all experimental groups,and male density increased with the incease of population density.The maximal male density and accumulative number of ephippia of M.irrasa occurred at 25℃,i.e.169ind./（200ml） and 1444ind./（200ml）.Relationship between temperature and the number of ephippia of M.irrasa was observed.Our results suggested that extreme temperature was not good for population growth of M.irrasa,and the formation of ephippia of M.irrasa was affected by temperature,food and population density together.