Effect of age, diet, diapause and juvenile hormone on oogenesis and the amount of vitellogenin and vitellin in the twospotted stink bug, Perillus bioculatus (Heteroptera: pentatomidae)

Abstract

Vitellogenic oocytes from Perillus bioculatus have two native vitellins, Vt1 and Vt2, with molecular masses of 553 and 228 kDa, respectively. The hemolymph contains a major vitellogenin, Vg, with a molecular mass of 528 kDa that consists of three apoproteins with masses of 177, 84 and 59 kDa, respectively. Antibodies to purified Vt2 reacted with ovary extracts, egg extracts and female hemolymph, but not with male hemolymph in immunodiffusion tests. Western blots showed that anti Vt2 reacted with both Vt1, Vt2 and with Vg. Vitellogenesis starts at an ovarian score of 12 at 2.4 days after emergence. The first cycle of egg development is completed in ovaries with a score of 112 at 7.7 days. During this 5.3 day period, the ovaries of a single female incorporated 1833 μg of protein to form vitellin. Vitellogenin levels start to increase in females 2.5 days after emergence and reached 17.8 μg/μl by 5.5 days. After 5.5 days vitellogenin levels fluctuated between 9.7 and 19.9 μg/μl. Most diapausing females contained no ovarian follicles in the vitellarium and their hemolymph contained less than 1 μg/μl of vitellogenin. Treating diapausing females with 1 μg of JH III increased vitellogenin levels over 120-fold. Insects maintained on a liver-based artificial diet had lower vitellogenin levels than the controls at all sample times and did not show an increase in vitellogenin concentration until 11.5 days. Treating insects on the artificial diet with 10 μg of JH III elevated vitellogenin levels to about a fourth of that found in prey-fed insects of a comparable age. This suggests that females fed the artificial diet have low levels of essential materials needed for vitellogenin production.