| Popis: |
The nature and the evolution of different lipids (phospholipids, glycerides, sterols) of Locusta migratoria migratorioides L. eggs during the embryo genesis, which requires 18 days, have been studied. These lipids were separated with a silicic acid column and identified by chromatography on silicic acid impregnated paper. The lipids, which, at laying, are 26 per cent of the egg dry weight (19·5 per cent of phospholipids, 78·5 per cent of glycerides, 2 per cent of sterols), show a total decrease of 31·2 per cent to form only 20·7 per cent at the end of embryonic development (phospholipids 31 per cent, glycerides 66 per cent, sterols 3 per cent). Our study shows that this fall is due only to the catabolism of glycerides. The phospholipids, consisting of cephalins (phosphatidylethanolamines for the most part and a few phosphatidylserines), lecithins, and of small quantity of lipids similar to sphingomyelin (we could not prove the existence of phosphatidylinositol), account for 19·5 per cent of the total lipids of the egg when it is laid (26·5 per cent of cephalins, 70·5 per cent of lecithins, 3·5 per cent of ‘sphingomyelin’). During the whole of embryogenesis they show no qualitative variation. During the first 8 days, they are transferred from vitellus to the embryo. Blastokinesis is marked by a decrease of 11 per cent of lecithins. The cephalins do not vary. We could not determine whether this degradation of lecithins occurs in the vitellus or in the embryo. The end of blastokinesis is marked by an increase of lecithins and cephalins up to the fifteenth day. Thus blastokinesis seems to play an important role in embryonic development, since its end permits the synthesis of phospholipids. After the fifteenth day there is an increase of cephalins whereas lecithins decrease. These facts can be related to the differentiation of tissues rich in phosphatidylethanolamines or in phosphatidylserines. All these phenomena are shown by a total increase of phospholipids which at the time of hatching constitute 31 per cent of total lipids (37·4 per cent of cephalins, 58·6 per cent of lecithins, and 4 per cent of ‘sphingomyelin’). The glycerides constitute at the beginning as well as at the end the majority of the lipids (respectively 78·5 per cent and 66 per cent of total lipids). It is their decrease (52 per cent) from the sixth day which is the cause of the total lipid decrease. This fall is only due to the catabolism of triglycerides, which constitute the most part (83 per cent of total esterified fat acids). The mono-and di-glycerides show no variation. |
