élevage de Vers à soie; bacologues; sériciculteurs; alimentation; production de soie; 4ème âge larvaire; croissance de l'organisme; glandes séricigènes; biochimie; acides aminés; digestion intestinale; feuilles de mûrier; synthèse de la soie; race européenne monovoltine Alpes; mûrier blanc
Abstract :
[en] The quality and the quantity of the food taken by the silkworm during the periods of tissues-growth, the period of "facultative" alimentation, in the middle of the 5th stage, have an important indirect repercussion on the quantity of the silk which will be spun. In the silkworm, the elaboration of fibroin by the silk glands is realiezd to the expense of some free amino acids of haemolymph. The amino acids that we used were essentially : glycine, aspartic and glutamic acids (either free or under the form of amids) sericin and threonine. These amino acids are from alimentary origin, some of them are lajd by in tissues when they are ingested before the time when the silk glands come into activity, that is to say till the middle of the alimentary-period of the 5th age. They are them released during histolysis which starts during the facultive alimentary period, and they are used for the silk synthesis at the same time when the amino acid component of blood is secured only by the progressive lysis of the tissues. The activity of the sericigenous glands is such that the quantity of used amino acids exceeds the quantity provided by histolysis. This disproportion induces an important decrease in the glycin concentration, in the aspartic and glutamic acids in the threonine and serine free in the blood. At the end of the spinning, the sericigenous glandular activity being ended, the amino acids content of blood gets back to the initial value. Among the other amino acids provided by the alimentation, histidlne does not have shere in the silk elaboration, neither directely nor indirectly. But the histidine content of blood is the object for a compensation which seems to stand against the decrease of the osmotic pression caused by the use of the other amino acids by the glands. Methionine which is synthetized from endogenous elements, as soon as the first defecation, seems to play the same part.
