Fine structure of the cocoon filaments of the silkworm differing relative amounts of sericin

• Published in: The Journal of Sericultural Science of Japan Vol. 56; no. 4; pp. 343 - 349
• Main Authors: MACHIDA, YUKIO, MORI, TADASU
• Format: Journal Article
• Language: English
• Published: The Japanese Society of Sericultural Science 1987
• ISSN: 0037-2455; 1884-796X
• DOI: 10.11416/kontyushigen1930.56.343

Cross sections of the cocoon filaments from several strains of the silkworm, Bombyx mori were observed by transmission electron microscopy. Vacuolar structures were seen in the paired core fibroin region covered with the sericin layer. Under higher magnification, the sericin layer of the cocoon filaments was clearly resolved into four sub-layers. The outer-most a-layer was shown to be the darkest and contained many bubble-like structures, and the second b-layer was seen as a bright zone. The c-layer corresponded to the widest region and was darkish but did not contain bubbles, while the d-layer adjacent to the core fibroin was a mixed region containing both sericin and fibroin. Measurement of the dimensions in a cross section gave a 3:1:12:1 ratio for the sericin layers a, b, c and d, but the ratio differed remarkably among the parts of a cocoon filament and also among the strains. There was a linear relationship between the degumming loss percentage of the cocoon shell and the ratio of sericin layers in the cross section of the cocoon filament.