Conclusions
Attacus atlas produces considerably heavier cocoons with three distinct layers. The intermediate layer formed the bulk (43 %) of the cocoons whereas the outer and in- ner layers accounted for 23 and 34 %, of the weight of the cocoon, respectively. Degumming was necessary to obtain fibers from the cocoons and the extent of degum- ming loss decreased from the outer to the inner layers. The amino acid composition in the A. atlas fibers was found to be considerably different than the amino acid composition in B. mori silk fibers. Fibers in the outer layer of the cocoons were relatively coarser than the fi- bers in the intermediate and inner layer. Breaking tenac- ity (3.6–4.3 g/den) of the fibers from the three layers of A. atlas cocoons was similar to that of B. mori silk but much higher than that of the common wild silks. Elon- gation of the A. atlas fibers was similar to that of B. mori silk fibers but much lower than that of the wild silks. The A. atlas fibers showed considerably higher attach- ment and proliferation of cells than B. mori silk and ex- tensive growth of F-actin demonstrating that the fibers were biocompatible. Overall, the ability of the A. at- las caterpillars to produce larger cocoons and silk fibers with properties similar to that of B. mori silk offers an opportunity to rear the A. atlas as alternative to the com- mon silks for commercial silk production.