Abstract
Changes of urea contents in the hemolymph from pupation to adult emergence were compared between silkworms fed on mulberry leaves and those fed on artificial diet. Urea-N contents in the hemolymph of pupae from larvae reared on artificial diet ranged from 600 to 1, 200μg per ml. On the other hand, ureá-N was hardly detected in the hemolymph of pupae from larvae reared on mulberry leaf. Urea did not accumulate in the pupal hemolymph, even when the larvae reared on artificial diet were subsequently fed on mulberry leaves only for 2 days before spinning. Urea content in the hemolymph of pupae reared on artificial diet varied with the silkworm varieties and dietary conditions, but it always exceeded the level of that in the hemolymph of pupae reared on mulberry leaves. In the eggs laid by adults reared on artificial diet, urea-N contents ranged from approximately 300 to 750μg per g. Furthermore, urea contents in the hemolymph of adults which laid a large number of nonfertilized eggs, were higher than those of adults which laid normal eggs.
