Interaction between chromatoid bodies and mitochondria in neoblasts and gonial cells of the asexual and spontaneously sexualized planarian, Girardia (Dugesia) tigrina

Abstract

Summary The interaction between chromatoid bodies and mitochondria in neoblasts of the asexually reproducing planarian Girardia (Dugesia) tigrina, as well as in oogonial cells of the spontaneously sexualized individual G. tigrina, was studied using transmission electron microscopy. Mitochondria-chromatoid body complexes (chromatoid bodies surrounded by several mitochondria) are typical of planarian neoblasts and oogonia. In many mitochondria contacting the chromatoid bodies in gonial cells, the outer mitochondrial membrane disappeared, and release of the mitochondrial matrix was observed. The mitochondial derivatives devoid of an outer membrane and initially containing cristae of the inner mitochondrial membrane apparently were integrated with the material of chromatoid bodies. These findings agree with our previous ultrastructural data on sea urchin, fish and holothurian gonial cells and also with the molecular evidence provided by other authors for the presence of mitochondrial ribosomal RNA in germline granules. It is proposed that the release of a mitochondrial matrix into the cytoplasm mediates the transport and incorporation of mitochondrial derivatives into chromatoid and germinal bodies where both mitochondrial and nuclear genome products are involved in structural organization and functioning of the macromolecular complex.