A Particular Nuclear Division Mechanism and Plasmodieresis in Euglena Terricola (Dang.) Lemm

SUMMARY

By performing cytogenetic investigations in several Euglena terricola (Dang.) Lemm. and Euglena clara Skuja populations, as well as in other species of Euglena, we found that besides the usual type of euglenoid division which was minutely described by DANGEARD (1901), HOLLANDE (1952) and LEEDALE (1966, 1967), and which we likewise evidenced in Euglena clara, a particular mechanism of nuclear division and plasmodieresis is to be found, which we evidenced in Euglena terricola. It is a nuclear division and plasmodieresis unique in the living world. This particular euglenoid division mechanism evidenced in E. terricola is, according to us, due to the biology of this species, which populates the waters most intensely polluted with organic detergents. It seems probable that as a result of genetic material endo-ploidy or polyteny, phenomena which disturb the normal euglenoid division mechanism and namely the nucleolus function, which during normal division elongates, assumes a dumb-bell shape, polarizing the cell, chromosomes placing themselves parallely with the elongated nucleolus (plates I and II). It is very interesting that in Euglena terricola we failed to evidence the normal euglenoid division type neither in natural nor in culture populations. In certain cases, in other species of Euglena too, aspects of this particular division mechanism and plasmodieresis appear, which were evidenced by us in Euglena terricola.

In principle, within this particular euglenoid division mechanism the nucleolus disappears in the early division stages, being restored at the end of division on account of the functioning of a nucleolar organiser chromosome. Within the framework of this particular euglenoid division mechanism, the complicated nuclear metamorphosis is described, which in entering into division assumes the characteristic shape of chromosome bearing horseshoe. The complicated chromosomal metamorphosis is evidenced, which from moniliform or rodlike shape, changes into the spherical shape. The plasmodieresis phenomenon is likewise described and unfolds according to two modalities, by longitudinal scission and by budding.