| Monocrotophos is a highly toxic organic phosphorus pesticide, not only having high acute toxicity and neurotoxicity to aquatic organisms, but aslo having impact on the reproductive and development of individual. Pre-job of our aboratory had proved that monocrotophos was found as a potential environmental estrogens, having reproductive toxicity, causing ultrastructure damage of goldfish testis, also affecting multi-generations breeding of zebrafish, it is suggested that the monocrotophos may have a negative impact to population dynamics of aquatic organisms. Lindane has a long half-life, history of usage, the one of the organochlorine pesticides with the highest detection rate in surface water in China, together with the organic phosphorus pesticide caused combined pollution in aquatic ecosystem, having a joint impact on population dynamics of aquatic organisms. To study the impact of pesticides on population dynamics of aquatic organisms, the key is to selection an experimental organism with short generation time, Chromadorina germanica with worldwide distribution, easy to cultivate, and a short generation time. Used as an organism to study the impact of pesticides on population dynamics, and many generations can be observed in a relatively short time.Therefore, using C. germanica as an experimental organism, Choosing monocrotophos, an organophosphorus pesticides with shorter half-life, and lindane, a organochlorine pesticides with longer half-life, to study the population dynamics changes, using individual endpoints such as fecundity, growth and development, and population endpoints such as intrinsic growth rate, population growth rate and sex ratio, under separate and combined exposure of the two pesticides pure. Meanwhile, using RAPD method and Nile Red fat staining in vivo with fluorescence quantificationm, the changes of genomic DNA polymorphism and intestinal fat storage of C. germanica were detected, caused by monocrotophos and lindane. Joint effects of monocrotophos and lindane on population dynamics, genome DNA polymorphism and intestinal fat storage of C. germanica were determined. The mechanism that population dynamics changes of C. germanica caused by monocrotophos and lindane was primary studied. The results could supply the experimental data to answer the effects of pesticides on aquatic ecosystems. Results showed:(1) The population dynamics of the first and second offspring of C. germanica were changed by monocrotophos. After exposed to 0.1, 1.0, 10.0, 100.0, 1000.0μg/L monocrotophos, the total fecundity of the parental and offspring were significant reduced, of the first and second offspring, egg fertilization rate and embryo hatchability reduced, embryonic development were delayed, deformity rate of L1 larvae was increased, the number of adults was reducing and the intrinsic growth rate and population growth were suppressed, sex ratio deviated from the one and more female. of which, after exposed to 1000.0μg/L monocrotophos, no second offsprings was observed.(2) The RAPD profiles of offsprings of C. germanica was changed by monocrotophos; value of polymorphisms of offspring C. germanica genomic DNA are as follows: 26.7%, 19.8%, 19.8% and 24.4% for 0.1, 1.0, 10.0 and 100.0μg/L monocrotophos.(3) Nile red fluorescence of intestine of C. germanica offsprings was changed by monocrotophos, fat storage of front and post part of intestine increased, but the middle part of intestine reduced; the fat storage of the whole intestine increased, treated by 100.0, 1000.0μg/L monocrotophos(4) The population dynamics, genomic DNA polymorphisms and fat storage of intestine of the first and second offspring of C. germanica were also changed by lindane. The total fecundity of the parental and offspring was decreased andegg fertilization rate was decreased, the number of adults was reduced, the intrinsic growth rate and population growth were suppressed, in the first and second offspring treated by 0.005, 0.05, 0.5, 5.0 and 50.0μg/L lindane; the embryonic development of first offspring was delayed in 0.5, 5.0 and 50.0μg/L lindane treatment, deformity rate of L1 larvae of first offspring was increased in 5.0 and 50.0μg/L lindane treatment. The value of polymorphisms of offspring C. germanica genomic DNA are as follows: 20.9%, 20.9%, 22.1%, 18.6% and 17.4% for 0.005, 0.05, 0.5, 5.0 and 50.0μg/L lindane. Fat storage of front and post part of intestine was increased, of middle part was decreased for 0.005, 0.05, 0.5, 5.0 and 50.0μg/L lindane. The fat storage of the whole intestine was significantly increased for 0.5, 5.0 and 50.0μg/L lindane.(5) The population dynamics, genomic DNA polymorphisms and fat storage of intestine of the first and second offspring of C. germanica were strongly changed for joint of monocrotophos and lindane. No first offsprings of C. germanica was observed in the highest joint treatment V. The value of polymorphisms of offspring C. germanica genomic DNA are as follows: 40.9%, 38.2%, 41.8% and 41.8% for joint treatment I, II, III, IV of monocrotophos and lindane. By comparing the results of monocrotophos, lindane separate treatment to the joint treatment, additive effects on the population dynamics, genomic DNA polymorphism and intestinal fat storage of C. germanica were found, after joint treated by monocrotophos and lindane.
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