| Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is a well-known aphidophagous, but also feeds on other small insects, such as eggs and larvae of Lepidoptera, whiteflies, mites and scale insects. Because of its characters, such as very prolificacy, long lifespan and voracious, H. axyridis is a potential biological natural enemies insect. In this paper, the structure of female reproductive system, ovarian development and oogenesis in H. axyridis were investigated. Effect of different diets on the development, oviposition and vitellogenesis of H. axyridis was studied. And then, in order to explore the reasons of poor fecundity of H. axyridis females on substitution prey, biochemical analyses were conducted on preys and ladybeetles. Aiming at offering theoretical reference and basis for developing the substitution prey and raising H. axyridis reproductive efficiency. The main results are as follows:1. Based on external morphology characteristics and the vitellines deposition conditions, the ovarian development in the adult stage of H. axyridis could be divided into 4 stages. The oogenesis was studied using histological techniques. Basing on the changes of the oocyte’s size, nucleus of the oocyte, follicle cells and the accumulation of vitellines, oogenesis in the adult stage could be divided into 3 periods which were oocytes differentiation, oocytes growth and the oocytes maturation. And the 3 periods could be divided into 7 stages.2. The vitellin of H. axyridis was extracted with 0.4mol/L NaCl and then precipitated in cold distilled water. The characterization of vitellin was carried out by Native-PAGE and SDS-PAGE analyses. The results shown that the vitellin had a native molecular mass of 625.9 kDa and was composed of four subunits, two large ones 154.6 kDa and 133.2 kDa, and two small ones 44.1 kDa and 40.0 kDa. Carbohydrates and lipids were found assoeiated with it. The content of insects’essential amino acid was 41.47%, and the higher contents between them was Lys and Val, which were 6.93% and 6.94%. The Glu and Pro were higher among all the species, which were 11.32% and 10.83%.3. The potential of rearing H. axyridis on 11 different diets was evaluated, and using Myzus persicae as control. The results indicated that Sitotroga cerealella eggs could satisfy the nutritional requirements ofH.axyridis larvae, and the freezing ones was better than the refrigerated ones. The duration of larvae and survival rate from larvae to adults were 10.9 days and 91.0%, respectively, on freezing S. cerealella eggs. They had no significantly difference with the control (10.4 days and 72.8%). Preoviposition of S. cerealella eggs were 18.2 days, which was significantly longer than control (8.1 days). The number of eggs laid was 424.7 and twofold higher in control (938.4). The freezing S. cerealella eggs could be used as supplementary diet to keep the larvae or adults of H. axyridis, when natural prey is inadequate or absent. The 9 artificial diets in this paper shown low values. The best one among them was Diet 7, which was prepared by a portion of fresh pork liver, honey, sucrose, olive oil, yeast extract and Vanderzant’s vitamin mixture. The viability from larvae to adults and number of eggs laid of H. axyridis fed on it were 17.6%and 231.3, respectively.17.6% females did not lay eggs.4. A polyclonal antibody against vitellin was prepared in male rabbit. After purification, HRP was used to mark the antibody, then ELISA was set up to detect vitellin content in fat body, hemolymph and ovary ofH.axyridis fed on freezing S. cerealella eggs and M. persicae The results suggested that the vitellogenin was synthesized in fat body and transferred to ovary. The content of vitellin in ovary of H. axyridis fed on freezing S. cerealella eggs was lower, because of its low content in fat body. But there was no difference between the contents of total protein in fat bodys of 2 treatments.5. Biochemical analyses were conducted on the proteins and lipids of these two different prey species as above. M. persicae were 2 times richer in amino acids than S. cerealella eggs (2718.7 nmol/mg vs1431.8 nmol/mg). Thus, the patterns of amino acids expressed in% of total amino acids were similar for the two kinds of prey. While, S. cerealella eggs were 2 times richer in fatty acids than M. persicae (77.3μg/mg vs 31.4μg/mg). The patterns were completely different for the two kinds of prey, aphids had high quantities of myristic acid (58.4%) and palmitic acid (18.7%), and S. cerealella eggs was high in oleic acid (54.0%), linoleic acid (14.1%) and palmitic acid (13.7%). The food source had no significant effect on amino acids composition of H. axyridis adults. The patterns of relative fatty acid content were also similar for females ofH. axyridis grown on M. persicae or S. cerealella eggs. Stearic acid, oleic acid and linoleic acid were higher in them. Significant differences were observed for myristic acid, it was 8.3% and 4.5% in newly-emerged and females at the first oviposition ofH. axyridis fed on M. persicae, but only 0.5% and 1.6% in them which fed on S. cerealella eggs. So the deficiencies in myristic acid could partially explain the poor fecundity of females grown on S. cerealella eggs.6. The variation to vitellin was studied by SDS-PAGE and direct ELISA during embryogenic and postembryonic development to H. axyridis. The results indicated that vitellin was degradated constantly during embryonic development, but some of them were retained after eggs hatched. |
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