The timings of vitellogenesis and choriogenesis in the Henosepilachna vigintioctopunctata oocytes

Abstract

In order to provide a biological basis for the development of population management strategies, a critical need is to better understand the reproduction of agricultural pests. In the current paper, we timed the previtellogenesis, vitellogenesis and choriogenesis processes in Henosepilachna vigintioctopunctata (Fabricius), (Coleoptera, Coccinellidae), a serious polyphagous defoliator damaging a wide range of crops in Solanaceae and Cucurbitaceae. The female reproductive system was comprised of two ovaries, two lateral oviducts, a median oviduct, a spermathecal sac and a genital chamber. Each ovary had an average of 28 (±0.4) telotrophic meroistic ovarioles. In the ovarioles of 4-day-old females, only previtellogenesis process was observed. The vitellogenesis occurred at 5 to 7 days after female emergence, while the choriogenesis took place at 8 and 9 days post eclosion. Copulation and oviposition occurred before and at 8 days post emergence. In order to confirm the observation, HvVgR and HvVg were identified and their expression was examined. HvVgR was abundantly transcribed in the ovary, whereas HvVg was richly expressed in the fat body. The temporal expression profiles showed that the high levels of HvVgR and HvVg were accompanied with the active accumulation of yolk proteins and the occurrence of intercellular spaces among follicle cells. Moreover, only one oocyte was observed per ovariole in active vitellogenesis. The observation demonstrates that oocytes are continuously matured and the oviposition persists in females from 8 days to at least 13 days post eclosion.