Effect Of Diet And Mating Status On Ovarian Development In An Omnivorous Bug Apolygus Lucorum(Hemiptera: Miridae)

Over the past10years, mirid bugs, formerly a group of secondary insect pest, have become keypests of cotton in China with increasing adoption of Bacillus thuringiensis (Bt) cotton. Studies aboutApolygus lucorum (Hemiptera: Miridae) on its reproductive physiology were rare because of its longbeen secondary pest on cotton. We studied effect of diet and mating status on ovarian development in A.lucorum. The results as followed:A female of A. lucorum had two clear ovaries, and each ovary contained seven yellowish ovarioles.The ovarioles were joined with the terminal filaments, forming a compact spindle-shaped structure.Each ovariole could be divided into four parts of terminal filament, germarium, vitellarium and pedicel.A. lucorum ovarioles were classified as meroistic telotrophic with nurse cells located at the apex of theovarioles. Based on the length of ovarioles, the developmental status of follicles and the deposition ofyolk protein, the development of A. lucorum ovary could be classified into five levels (Ⅰ-Ⅴ). Nodeveloped follicles in the vitellarium were observed for freshly emerged females. When the ovariesdeveloped into levelⅡ, oocytes with visible yolk protein could be seen in the vitellarium. In general,the females of A. lucorum at preoviposition period had ovaries at the levels of I–III, and the females atoviposition period had ovaries at the levels of IV–V.The ovarian development in A. lucorum adult females was investigated when they were fed ongreen beans, combination of green beans and Helicoverpa armigera eggs or H. armigera eggs. Ourresults showed the morphology of the ovaries of A. lucorum females was not affected by food sources,but their ovary development was significantly affected by feeding on different diets. Females fed ongreen beans or combination food of green beans and H. armigera eggs had larger ovaries and theovarioles contained larger numbers of oocytes compared to those fed on H. armigera eggs. The ovariandevelopment significantly delayed for females fed on H. armigera eggs. Females fed on combinationfood of green beans and H. armigera eggs had significantly higher number of follicles at previtellogenic,vitellogenic and mature stages throughout the whole adult period compared to those in Gb or Hetreatment.In A. lucorum, mating stimulated ovarian development and oviposition. During preovipositionperiod(ages before7days after emergence), mated A. lucorum females had higher number of follicles atvitellogenic and mature stages compared to virgin females. Furthermore, the ovary scores were alsosignificantly higher for mated females during this period. When grown into oviposition period, unmatedfemales laid few eggs with larger number of mature follicles in ovaries, especially20days later afteremergence than mated females.The cDNA sequence of vitellogenin was cloned from A. lucorum. The full length of cDNA in A.lucorum was6131bp with5988bp of open reading frame. The molecular weight deduced by aminoacid sequence was218.3kDa, coded by1996amino acid including an17-residue putative signalpeptide. The calculated isoelectric point was9.02.3’ non-coding area was86bp,5’ non-coding area was 57bp. The expression profile revealed that the amount of Vg mRNA were significantly influnencd byfood and mating status.In conclusion, systematic studies on A. lucorum ovarian development revealed effect of diet andmating status on ovarian development. The results indicated that combination of plant and insect eggs asfood sources facilitates ovarian development in A. lucorum, and mating stimulated ovarian developmentand oviposition. Moreover, the cDNA sequence of vitellogenin was cloned from A. lucorum. Thoseresults will be helpful for monitoring and forecasting on the pest population.