Do germ line cells in Allacma fusca (Insecta, Collembola, Symphypleona) have a higher metabolic rate than somatic cells

Stereological analysis of the ultrastructure of primordial germ cells (PGCs ) and the somatic (ectoderm) cells in two developmental stages of embryos a nd freshly hatched juveniles of Allacma fusca have shown great differences in mitochondria volume density (vd) between the two types of cells. In youn ger embryos (migration phase of the PGCs) the vd of mitochondria in the cyt oplasm of the PGCs is 74.64% higher than in the ectoderm cells. In older em bryos, (PGCs in the gonads) the vd of mitochondria is 123% higher than the corresponding value for the somatic cells cytoplasm. In the juvenile the vd of mitochondria in the ectoderm cells grows twice but is still only 2/3 of the value for the PGCs. On the basis of papers describing a direct relatio nship between stereological and physiological results the authors conclude that the metabolism of the primordial germ cells during embryonic developme nt of Allacma fusca is much higher than that of the somatic ones. If the ab ove conclusion is correct, the results presented here confirm the "disposab le soma theory" (KIRKWOOD & HOLLIDAY 1979).