title: Presence of intranuclear micro cables in a primitive dinoflagellate protist: morphological description and discussion of their possible evolutionary significance.
abstract: An intranuclear "cable" system has been demonstrated in the nucleus of the so-called primitive dinoflagellate Prorocentrum micans E. by means of a new cryofixation technique. Numerous cables are situated between the chromosomes. They are composed of several helically twisted filaments of 50-60 A diameter. The diameter of the cables varies from 200 A. In most dinoflagellates the microtubular spindle is permanently extranuclear, whereas this filament system is always located in the nucleus and is permanently surrounded by the nuclear envelope. The possible function of these cables is discussed. In evolutionary terms, such a complex fibrillar system must be taken into account as much as the microtubular system, particularly in these cells which are still considered as lower eukaryotes, although the special position of the dinoflagellates becomes more and more separate.
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002467:Cell Nucleus / Q000648:ultrastructure*; D002875:Chromosomes / Q000648:ultrastructure; D004141:Dinoflagellida / Q000648:ultrastructure*; D008854:Microscopy, Electron