Light and Electron Microscopic Study on the Development of Nosema Bombyics Naegeli in the Midgut of Silkworm Bombyx Mori L.

Abstract

Infection effect of Nosema bombycis on the midgut of silkworm Bombyx mori and subsequent appearance of spores and the performance of larvae was studied. Autopsy of larvae showed white pustules on the surface of midgut at 5 days of post infection (pi). At later stage, important organs like midgut, silk gland and gonads reduced in size and all these organs showed white pustules. Light microscope observation of pustules revealed enormous spores. Spore multiplication was at a faster rate in young larvae. Infection of the adult larvae resulted in pebrinized pupa and moths. Larval weight, cocoon weight and cocoon shell ratio reduced as the post infection period increased. Transverse sections of midgut showed N. bombycis infection limited to a few columnar cells at 3-5 days of pi. At 7 days pi, cell volume increased, cells were swollen and elongated. Heavily infected cells looked like sacks filled with parasite and the apical region of certain cells were bulging into the gut lumen. Later at 8-9 days of pi, spores or its developing stages leaked into the lumen either freely or enclosed within the globules of host cytoplasm. Besides columnar cells, development of N. bombycis was observed in the regenerative cells and rarely in goblet cells. Development of N. bombycis was also observed in both longitudinal and circular muscles at the late pi period. The histopathological changes, deformities and spore production time in the host were all influenced by the spore dosage and age of the host.

Journal of Plant Protection Research

“…Some studies show that chemical treatments performed long before mulberry plantations were established in a given place resulted in long-term accumulation of toxins in the soil. The effects of those accumulations affected larval mortality up to 36 months after sprayings (Jyothi et al 2019). Even small amounts of pesticides can have a significant impact on different aspects of development and rearing performance of silkworms.…”

Infectivity of Two Isolates of Microsporidia on Silkworm (Bombyx mori L.) in South Sulawesi

“…This result similar to Rao et al (2004) that suggests that at a dose of 10 7 spores ml -1 mortality can reach more than 50% after infection. While studies of Jyothi and Patil (2011) showed that fourth instar mortality was 86% at a concentration of 1×10 6 spores larva -1 , infectivity can reach 90% at a concentration 1.52×10 6 spores ml -1 . …”

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“…This result similar to Rao et al (2004) that suggests that at a dose of 10 7 spores ml -1 mortality can reach more than 50% after infection. While studies of Jyothi and Patil (2011) showed that fourth instar mortality was 86% at a concentration of 1×10 6 spores larva -1 , infectivity can reach 90% at a concentration 1.52×10 6 spores ml -1 (Chakrabarty et al, 2012).…”

“…The new external symptoms were observed after day 10 DAI and mortality of larvae increased in both inoculation instar 3 or 4. Histopathological study by Jyothi and Patil (2011) shows the midgut has formed sporoblast phase on the third day after infection. Hossain et al (2012), sporo plasma gradually increased in size and developed into meronts 24-48 hrs after inoculation.…”