钩虾等位酶基因型对马拉硫磷致死性响应研究

Lethal Responses Among Allozyme Genotypes of Gammarus pulex to Acute Exposure to Malathion

钩虾的Idh-1、Idh-2、Pgm、PgiAo-1和Ao-2基因座位具有多态性,从平均每个基因座位的等位基因数(A=2.6～2.9)、多态基因座位百分率(P=71.4%)、平均观察杂合度(Ho=0.226～0.246)和平均期望杂合度(He=0.394～0.409)4个参数可知,钩虾具有较高的遗传多样性,适合于农药马拉硫磷作为选择因子用于对具有不同基因型的个体的致死性差异研究。本实验以钩虾为对象,通过急性毒性实验方法,研究了钩虾等位酶基因型与马拉硫磷急性致死作用的关系。结果表明,供试钩虾用10-6g·L-1马拉硫磷溶液处理382只,96h后死亡率为68.8%。分别对存活个体和死亡个体的Idh-1、Idh-2、Pgm、PgiAo-1和Ao-2基因座位进行等位酶分析以确定每个个体的基因型。列联表χ2检验表明:马拉硫磷对Idh-1、Idh-2、Pgm和Ao-2各基因型个体的选择呈现随机特征,各基因型与死亡率未见显著的相关(P>0.05)。但在Gpi和Ao-1基因座位上,Pgi-AC和Pgi-AD基因型死亡率间存在显著差异;Ao-1-AC和Ao-1-BB、Ao-1-CC基因型死亡率之间存在显著差异。显示马拉硫磷的致死作用对Pgi和Ao-1基因座位的不同基因型呈现出非随机特征,Pgi-AD和Ao-1-AC基因型很可能与钩虾对马拉硫磷的耐药性有关。

A population of Amphipods Gammarus p ulex from Yuanping City, Shanxi Province in China were found polymorphie at the loci of Idh-1, Idh-2, Pgm, Pgi, Ao-1 and Ao-2, using horizontal starch gel eleetrophoresis. The data of the mean number of alleles per locus （A = 2.6-2.9）, percentage of polymorphic loci （P = 71.4% ）, the observed mean heterozygosity （Ho = 0.226-0.246）and the expected mean heterozygosity（Ho = 0.394-0.409 ）suggest that this population possesses sufficient genetic diversity, which makes it feasible for studying the possible differential mortality among the individuals of various genotypes aeutely exposed to malathion, the pesticide commonly found in agricultural runoff. A total of 382 G. pulex individuals were exposed to malathion at 10^-6g·L^-1 to achieve a mortality of 68.8% after 96 hours followed by allozyme analysis to identify the genotypes of each individual. Contingency table x^2-tests showed that malathion displayed random lethal effects among the genotypes at Idh- 1, Idh-2, Pgm, Pgi and Ao-2, where no correlation between the genotype and lethality was observed （P〉 0.05 ）. However, significant differential mortalities were observed in the following genotype pairs ： Pgi-AC （ 93 % ）vs. Pgi-AD （ 25% ）, A o- 1- AC （ 37% ）vs. A o- 1 -BB （ 69% ）, and A o- 1 -AC （ 37% ）vs. A o- 1 -CC （ 72% ）. Since the sample size of Pgi-AC （ 27 ）and Pgi-AD （ 8 ）may not be sufficiently large further exanfination is needed. At the loci of A o-1, under the assumptions of 1 ）the presence of uniform biological characters other than A o-1 genotypes, and 2 ）the presence of allelic interaction and heterozygotic vigor for the alleles of A o-1-A and A o-l-C, it is expected that Ao-I-AC would display lower mortality than Ao-I-CC when exposed to malathion. The data obtained from the study were found consistent with such reasoning, which suggests that the correlation of A o-1-AC genotype to the resistance to pesticide malathion in G. p ulex. The data imply that monitoring the dynamics of Ao-1-AC genotypes and perhaps Ao-1-A allele frequency may be useful in evaluating the resistance potential of this population against malathion exposure.