The effect of thyroxine on silk gland and the effect of two thyroxine-treated mulberry species feeding on silk quality in the silkworm Bombyx mori (Lepidoptera: Bombycidae)

The influence of feeding mulberry leaves treated with thyroxine to the growth of the silk gland, and the effect of two different mulberry species, that is, Morus nigra and Morus multicaulis treated with thyroxine on silk quality in the silkworm were studied. The silk glands from thyroxine treated Bombyx mori larvae weighed heavier than control. The weight of the posterior silk gland, where fibroin is synthesized, increased significantly compared to the anterior and median silk glands. No difference between thyroxine treatment on the second instar and fourth instar larvae in terms of silk gland weight was observed. Different mulberry species treated with thyroxine fed to silkworm larvae, affected silk quality. Higher silk tenacity and elongation were observed when silkworm larvae were fed thyroxinetreated M. nigra, while silkworm larvae fed on thyroxine treated M. multicaulis produced longer unbreakable filament.