| Phytoseius persimilis Athias-Henriot(Acari: Phytoseiidae), a obligatory predator for spider mites(Tetranychidae), is widely used for the biological control spider mites in greenhouses or orchards. Its reproductive mode is strange and rare, called “Paternal Genome Loss(PGL)”, because both diploid females and haploid males arise from fertilized eggs. People want to improve the production and application’s quality of predatory mite, making it necessary to study the reproductive mode and sex determination. As a result, there are some experiments in our research: Process of spermatheca produce and disappear; Effect of spermathecal change on oviposition and sex radio; Role or function of paternal chromosomes; Duration of heterochromatinization in paternal chromosomes.In first section, we designed the experiment of effect of mating duration on volume of spermatheca, oviposition and sex radio. A single completely mating, virgin female and male who are less than one day’s adulthood, was average of 112.8±1.2min. With the mating duration prolonged, fertilized female had bigger spermathecal and outputted more eggs, but offspring’s sex ratio was steady. The relationship between volume of spermatheca and number of eggs was fitted with nonlinear regression. We acquired a key point of volume of spermatheca that was 1159um3. Only reached the point can fertilized female output eggs. The relationship between number of eggs and female-all rate was fitted with logistic curve, which we acquired a maximum female-all radio that is 0.861. Process of spermatheca disappear was divided into three stages, first of which is disappear stage of the interspace spermathecal from 2.4h to 4h after mating begin, second of which is preparation stage from 4h to 8h after mating begin, and last of which is transfer stage of spermatid from 12 h to 24 h after mating begin. At 24 h after mating begin, volume of spermathecal reached the key point of 1159um3, which indicated the end of spermatid transfer stage. In addition, we noticed significant difference about length, width and ength-width ratio of eggs in the aspects of gender. In other word, male destined eggs are thin and small, and female destined eggs are fat and bigger. Researched the process of spermatheca produce and disappear revealed inner connection among reproductive parameters, which is in favour of reproduction.In second section, we studied the effect of irradiated several stages of Phytoseius persimilis Athias-Henriot via γ-ray on reproductive parameters, then speculated role of paternal chromosomes and duration of heterochromatinization. Survival unmated irradiated mites need to mate with normal mites in test. Then we need to record the number of eggs and gender of egg every day. Finally we need to test whether offspring can lay eggs. The results are as follows: under 160-640 Gy, unmated irradiated male mated with normal unmated female, whose offspring’s all were male and only 1/3 were fertile; under 45-90 Gy, unmated irradiated female mated with normal unmated male, whose offspring’s female-all ratio were decrease with increasing of irradiated dose, and who couldn’t lay eggs at 90 Gy. Irradiated female, before oviposition and after copulation, whose offspring’s female-all ratio ranged from 0.78 to 0.85. Irradiated eggs, at 24-48 h age of eggs, developed for adult mites, whose female-all ratio were increase with increasing of irradiated dose. In according with the test, we can speculate as follows: paternal genome was activated, formed gamete and decided gender; duration of heterochromatinization in paternal chromosomes may be the duration from egg shell forming to 12 h age of eggs. In the research, we explain the mechanism of sex determination via paternal genome, which is in favour of the mechanism of sex determination and biological evolution. |
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