[Volume variations and DNA content of the nuclei ofScapsipedus marginatus Afz. and Br. (Orthoptera, Gryllidae) during embryogenesis].

The average volume of the nuclei in the egg ofScapsipedus marginatus varies from 3101 μ3 at the tetra-nucleate cleavage stage, to 40,7 μ3 in the hatching embryo, with a constant decrease throughout development. The nuclear volume of neuroblasts remains constant; in the pleuropodia, it increases from 190 to 561 μ3 and decreases rapidly before hatching.The nuclei of the amnion derive from peripheral nuclei of the germ disk. After a small increase during anatrepsis, their volume decreases until the degeneration of this membrane.The serosa shows a great nuclear volume increase during the first three days of incubation, then a rapid decrease during its disappearance. Yolk cells present an important increase of their nuclear volume which remains high.Estimation of DNA content of the different nuclei at about the 96 hour stage, shows that those whose volume increases are polyploid. Amnion nuclei remain diploid together with neuroblasts. The relation between nuclear increase, polyploidy and physiological functions shows that the amnion is not involved in a particular secretory activity.Estimation of DNA content of the nuclei ofGryllus domesticus andLocusta migratoria at the same developmental stage give comparable results. The degrees of polyploidy found inGryllus are the same as inScapsipedus. InLocusta they are higher, yolk cells attaining values up to 128 C.