Studies on ultra structure and life cycle of Nosema assamensis (Protozoa: Microsporida), a parasite of muga silkworm, Antheraea assamensis Ww.

摘要

The muga silkworm, Antheraea assamensis Ww., produces golden yellow silk and primarily confined to Assam, India. Nosema assamensis, a pathogenic microsporidian cause pebrine disease in A. assamensis. Detailed morphology and life cycle stages of N. assamensis in light and electron microscopy were studied. Spores of N. assamensis were elongated, 4.375+or-0.051 micro m in length and 2.681+or-0.022 micro m in breadth. Length and breadth ratio was 1.636+or-0.025 and volume of a mature spore was 16.450 micro m3. The spore contained fibrous hard coating and slight concavity at the middle as found in SEM. The main components of the spore, sporoplasm, polar filament, polar cap, anterior and posterior vacuole and spore shell were observed in TEM study. The polar filament run an oblique course backward from its base at the centre of the polar sac, narrowed slightly in diameter gradually upto the end and formed a coil in the peripheral layer of cytoplasm. Extra-cellular binucleate Plannont and intra-cellular binucleate, tetranucleate and octanucleate Schizont/Meront were observed in TEM study. The number of coils was 9-10. Life cycle of N. assamensis includes two distinct stages, spore and vegetative. The life cycle is completed in 6-8 days in cold climate and in 5-6 days in hot weather.