Structural Characterisation of the Silk Gland of the Endemic Silkworm, Antheraea assamensis Helfer

ABSTRACT Silkworms spin the highly prized and versatile silk among all the silk‐secreting insects. The silk gland of these silkworms is the most efficient protein synthesizing system yielding a good variety of silk cocoons. Anthereaea assamensis Helfer is an endemic and unique non‐mulberry silkworm species belonging to the Brahmaputra valley of Assam and adjoining hilly areas. Herein this study, the silk gland was dissected out and divided into three distinctive parts: posterior (PSG), middle (MSG) and anterior (ASG) silk gland. Various microscopic techniques were adopted to understand the histological and ultrastructural components of the silk gland along with the flow of liquid silk in it. The fluorescence microscopic examination of the three silk gland parts showed nuclear ramification with an increasing pattern during the 4th and 5th instars. Light microscopic study of the PSG and MSG showed a tight secretory nuclear structure with a distinct epithelium and an unorganised, thin epithelial structure with large secretory vesicles, respectively. The ultrastructural study of the 5th instar matured larval PSG displayed a uniform and thick layer of basement membrane. MSG showed similar characteristics with the occurrence of sparsely distributed infoldings. This first comprehensive organisational study of the silk gland parts of A. assamensis Helfer revealed the structural features responsible for silk synthesis, storage and its secretion.