Effects of pH on embryonic and larval development of Capitulum mitella Linnaeus

Effects of pH(5.0,5.5,6.0,6.5,7.0,7.5,8.0,8.5,9.0 and 9.5) on the embryonic development and larval development of Capitulum mitella were investigated under controlled laboratory conditions.The pH affected significantly not only the development time and hatching rate of embryos but also the survival rate and metamorphosis rate of larvae.At pH 5.0,embryos of Capitulum mitella couldn't hatch,but at pH 5.5-9.5,it could hatch in different degrees.At pH 6.0-8.5,Capitulum mitella had the shortest development time(6 d),and at pH 7.0,Capitulum mitella had the highest hatching rate.On the basis of development speed and hatching rate of embryos,the optimum pH for embryonic development was 7.0-8.0.Larvae could develop and metamorphose at pH 5.5-8.5,but when the pH was lower than 5.0 or higher than 9.0,it couldn't develop normally.According to larval survival rate and metamorphosis rate of Capitulum mitella,the optimum pH for larval development was 7.5-8.5.