pH值对日本三角涡虫种群增长、无性生殖及6种酶活力的影响

EFFECT OF MEDIUM pH ON POPULATION GROWTH,ASEXUAL REPRODUCTION AND ACTIVITY OF SIX ENZYMES OF DUGESIA JAPONICA

应用种群累积培养法,就培养液的pH值对日本三角涡虫的生存、种群增长、无性生殖以及涡虫超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-PX)、乳酸脱氢酶(LDH)、Na+-K+-ATP酶和Ca2+-Mg2+-ATP酶等6种酶活力的影响进行了探讨。结果表明,涡虫存活的pH上限为11.0,下限为3.0,涡虫存活的最适pH范围为4.5—8.5;pH值对涡虫种群增长有显著影响,种群密度及种群瞬时增长率均随pH的不同而明显改变。培养27d后,pH4.0—9.0时涡虫种群为正增长:pH4.5—6.5时,涡虫种群密度最高,pH7.5—8.5时次之,pH7.0时较低,pH4.0和9.0时最低;而pH9.5时为负增长。当pH值偏离7.0(偏酸或偏碱)时CAT、GSH-PX、Na+-K+-ATP酶和Ca2+-Mg2+-ATP酶活力整体均呈现增加的趋势,而SOD和LDH活力整体呈下降趋势。pH值偏离7.0(偏酸或偏碱)时涡虫6种酶活力均产生明显的变化,这与pH4.5—6.5和pH7.5—8.5时涡虫具有比pH7.0实验组涡虫较高的无性横裂生殖率之间可能存在一定的内在联系。本文研究结果可为实验室培养日本三角涡虫提供适宜的pH值指标。

The planarian Dugesiajaponica has a very wide distribution throughout fresh water body in China,especially in mountain streams. Because of the advantages of easy laboratory culture and fast asexual reproduction rate, Dugesia japonica is generally used as an experimental animal for cell biology, reproductive biology and stem cell as well as animal regeneration research, pH is one of the important factor affecting population dynamics, reproductive and other life activities of aquatic organisms, and is also the basic laboratory culture condition of planarian. However, there were no reports about the effect of pH on planarin asexual reproduction and population dynamics. The purpose of the present study was to make certain appropriate pH value for large-scale laboratory cultivation of the planarian. In addition, the study can provide the first-hand information for the in-depth research about planarian adaptability to the environment. With the method of population accumulation culture, the effect of medium pH on survival, population growth, asexual reproduction and the activities of superoxide dismutase （ SOD）, catalase （ CAT）, glutathione peroxidase （ GSH-PX）, lactic dehydroge- nase （LDH）, Na^＋ -K^＋ -ATPase and Ca^2＋ -Mg^2＋ -ATPase of Dugesiajaponica was observed. The result indicates that the threshold of pH is 3.0-11.0,the appropriate pH range is 4.5-8.5. pH had evident effects on planarian population growth, population density and population instantaneous growth rate varied obviously with different media pH. After 27 days, the planarian population increased positively at pH 4.0-9.0, and at pH 4.5-6.5, the planarian population density was the highest, at pH 7.5-8.5, it was higher, at pH 7.0 was lower, and at pH 4.0 and pH 9.0, it was the lowest;whereas, at pH 9.5 the planarian population increased negatively. Planarian at pH 7.0 is in very good condition （ such as normal feeding and locomotion behavior, maintaining a certain asexual reproductive rate and zero mortality）, but the asexual reproductive rate of planarian at pH 7.0 is lower than that at pH 4.5-6.5 and pH 7.5-8.5. It is possibility that the higher asexual reproduction rate of the planarians at pH 4.5-6.5 and pH 7.5-8.5 than that at pH 7.0 is the response of planarian to the intimidation of acidity or alkalinity, another possibility is that the moderate pH value for planarian survival is not consistent with one for asexual reproduction by transverse fission. When media pH departed from 7.0 （media pH becomes acid or alkali）, the activities of CAT, GSH-PX, Na^＋ -K^ -ATPase and Ca^2＋ -Mg^2＋ -ATPase had the increasing trend, while the activities of SOD and LDH had the decreasing trend. That is to say, the activities of the planarian＇ s six enzymes all changed evidently with the departure of media from pH 7.0. Especially, planarian population density in the range of pH 4.0-9.5 correlated positively with the level of CAT activity which is deemed as an important indicator of antioxidant level of organisms. For example, the formula of the regression relationship between CAT activity （Y） and planarian population density （X） at the 27^th day is Y = 0.706 X ＋ 1. 567 （ R^2 = 0. 614, p = 0. 003）. Furthermore, the level of CAT activity at pH 4.5-6.5 and pH 7.5-8.5 is 3-8 times higher than that at pH 7.0. Inverse environment usually causes the raise of antioxidant enzyme level, and it was a hint that pH 7.0 is the most suitable pH value for planarian survival.